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190 records found
1.
Džubinský, M., Y. Sidor, et al. (2004). "Kinetics of
columnar abnormal grain growth in low-Si non-oriented electrical
steel." Materials Science and Engineering A 385(1-2):
449-454.
Decarburising annealing in the two-phase region is a well-known method to
provide abnormal columnar grain growth in non-oriented electrical steel.
Previous investigations have revealed that columnar-grained material
produced in this way has an increased intensity of the “random
cube” 1 0 0 <0 v w > and reduced 1 1 1 <u v w >
deformation texture components in comparison with the same material with a
typical equiaxed microstructure. In the present paper, the kinetics of the
microstructure and texture development during the columnar grain growth is
investigated by means of electron backscatter diffraction with emphasis on
the early stages of the process. It has been found that texture changes
reflect the character of the columnar grain growth when with further
propagation of the columnar grains from the surface to the midplane the
global texture becomes similar to the one of the near surface region in
primary recrystallised material.
2.
Díaz-Fuentes, M., E. Novillo, et al. (2004). Cold Rolled
Microstructure and Its Evolution during Recovery and First Recrystallisation
Stages in Low Carbon Steels. Second Joint International Conference on
Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France,
Trans Tech Publications Ltd.
During annealing of cold rolled steel sheets, the evolution of the texture,
to produce the characteristic texture of a recrystallised material, depends
on a series of factors, including the starting deformation texture,
composition and processing conditions. In the present work, electron
backscattered diffraction (EBSD) techniques have been used to investigate
the deformation substructures being developed by cold rolling into grains
belonging to different texture components. The strain localisation, the
deformation banding, the spread in orientation into grains with different
orientations are some of the aspects that have been considered. Annealing
cycles at different temperatures have also been carried out in order to
promote recovery and initial stages of recrystallisation. The obtained
substructures have been compared to the as-cold rolled ones. It has been
observed that recovery induces the dislocation structures to arrange into
subgrains. Associated to the ND fibre, a network of relatively high angle
boundaries develop within the subgrain structure. The recrystallisation
nuclei have been observed to evolve from such a network.
3.
Da Costa Viana, C. S., A. L. Pinto, et al. (2006). "Study of the
recrystallization of ferritic steels using Electron Backscatter Diffraction
(EBSD)." Metalurgia and Materials 62(565): 155-157.
Electron bockscatter diffraction EBSD is a powerful technique to study
recrystallizotion in steels. The present paper presents a few examples of
the use of conventional and high resolution EBSD to follow the
microstructural changes developed during recrystallization of two ferritic
steels.
4.
da Silva, M. D. C. A., M. F. De Campos, et al. (2004). Deformation Texture
in a Go Steel Rolled at 0, 22.5, 45, 67.5 ad 90 Degrees to the Original
Rolling Direction. 59 deg Congresso Anual da Associacao Brasileira de
Metalurgia e Materiais: 59th Annual ABM International Congress, Sao Paulo,
Brazil, Associacao Brasileira de Metalurgia e Materiais.
This paper evaluates deformation inhomogeneities in steels. To constrain the
variables, the starting point is a sample with a very specific crystal
orientation: a grain oriented 3%Si steel, with a strong (110) 001 Goss
texture. Samples were cold rolled with 25% area reduction, in different
angles relative to the original 100 direction. Different deformation
structures are observed, by optical microscopy and by SEM equipped with EBSD
Hardness measurements were also performed. Deformation twins are easily
observed in samples rolled at 0 and 22.5 deg relative to the original
Rolling direction (RD). The higher the angle, less twins are observed.
Plastic deformation induced the presence of {112} components.
5.
Daaland, O. and E. Nes (1996). "Origin of Cube Texture During
Hot-Rolling of Commercial Al-Mn-Mg Alloys." Acta Materialia
44(4): 1389-1411.
Investigation of samples taken at different gauges during multi-pass hot
rolling has been made with emphasis on characterisation of the
through-thickness variation in microstructure and texture. The evolution of
the cube texture ((001),(100)), which is a major cause of anisotropy after
hot rolling is of particular interest. In the present study a detailed
investigation of the origin of the cube texture component during hot rolling
has been performed. Information on the characteristics of this special
crystallographic orientation during the hot rolling operation has been
obtained by applying the electron back scattering pattern (EBSP) technique
in SEM. The results show that the cube orientation is metastable during hot
deformation in the sense that large fractions of the cube are able to
survive through heavy reductions without rotating towards the stable texture
components. Cube grains, which during a few hot rolling passes get flattened
to a critical thickness, subsequently serve as sites for the nucleation of
second generation cube grains.
6.
Dabritz, S., E. Langer, et al. (1997). "Combined Use of Lattice Source
Interferences and Divergent Beam X-Ray Interferences to Investigate the
Microstructure of Ion-Bombarded Cu-Sn-Diffusion Zones." Fresenius
Journal of Analytical Chemistry 358(1-2): 148-153.
7.
Dabritz, S., E. Langer, et al. (1999). "New Observation Method for
Divergent Beam X-Ray-Diffraction Patterns." Journal of Analytical
Atomic Spectrometry 14(3): 409-412.
8.
Dabritz, S., E. Langer, et al. (2000). A comparison of lattice-source and
divergent-beam X-ray interferences as well as electron backscattering
diffraction for the determination of crystal parameters. Microbeam Analysis
2000. D. B. Williams and R. Shimizu. Bristol, Institute of Physics
Publishing: 193-4.
9.
Dabritz, S., E. Langer, et al. (2001). "Kossel and Pseudo-Kossel CCD
Pattern in Comparison with Electron Backscattering Diffraction
Diagrams." Applied Surface Science 179(1-4): 38-44.
10.
Dabritz, S., H. Horn, et al. (1999). "Detection of Crystal-Lattice
Defects in Microranges of Copper by X-Ray Interferences." Journal of
Analytical Atomic Spectrometry 14(3): 487-492.
11.
Dabritz, S., V. Hoffman, et al. (1986). "Investigation of the
Crystalline State of Identical Sample Domains by Means of Devergent
X-Ray-Beam Technique in the Direction of Transmission and Reflection in the
Scanning Electron-Microscope (SEM)." Crystal Research and Technology
21(12): 1531-1539.
12.
Dahle, A. K., C. Dinnis, et al. (2004). Recent progress in understanding
eutectic solidification in aluminum-silicon foundry alloys. Solidification
Processes and Microstructures: A Symposium in Honor of Wilfried Kurz,
Charlotte, North Carolina, USA.
It is now well established that three different eutectic solidification
mechanisms may occur in Al-Si foundry alloys. The operation of each
mechanism can be controlled by altering the chemical composition and casting
conditions. Recent research has focussed on the understanding of the
mechanisms determining the eutectic solidification mode by investigating the
growth mechanisms in ultra-high purity and commercial purity alloys, the
effect of a wide range of different potential modifying elements and
investigating the eutectic nucleation mode. It is concluded that nucleation
of eutectic grains is prolific in unmodified commercial purity alloys. In
contrast, high-purity alloys have relatively few nuclei and only a few
eutectic grains nucleate. Nuclei can also be removed, or rendered inactive,
by the addition of modifying elements to commercial purity alloys. There is
a relationship between the number of eutectic grains and the morphology of
the eutectic because the growth rate of the eutectic depends on the surface
area, The three eutectic solidification modes have widely differing spatial
distributions of growing eutectic and therefore significant effects on the
feeding efficiency of the alloys. Porosity is significantly affected by
eutectic solidification mode and there is a direct relationship between
them.
13.
Dahle, A. K., K. Nogita, et al. (2001). "Eutectic nucleation and growth
in hypoeutectic Al-Si alloys at different strontium levels."
Metallurgical and Materials Transactions A 32(No. 4): 949-60.
14.
Dai, Z., C. Bednarski-Meinke, et al. (2004). "Heteroepitaxial diamond
film growth: the a-plane sapphire–iridium system." Diamond and
Related Materials 13: 552-556.
A substrate system with suitable physical and chemical properties is a
necessary component for achieving large- scale heteroepitaxial diamond
growth. We have developed a two-stage process to produce (001) diamond films
using a- plane (112¯0) α -Al2O3 (sapphire)
as a substrate. Epitaxial (001) iridium films are first grown on terraced,
vicinal a-plane sapphire by ultrahigh vacuum electron-beam evaporation at
950°C. The epitaxial relationship, Ir(100)
//Al2O3(1120) with Ir[011]
//Al2O3 [1100], was determined by analysis of X-ray
and electron backscattering diffraction. For a 300-nm thickness of Ir, a
(200) rocking curve yielded a linewidth of 0.2°. After transfer to a CVD
system, a diamond film was grown on the Ir layer by low-pressure chemical
vapor deposition using methane and hydrogen. A key step in the process is
the initial exposure of the epitaxial Ir to a d.c.- biased plasma that leads
to uniform coverage of the surface by a dense array of diamond crystallites
prior to growth. A subsequent growth step for approximately 60 min yields a
continuous and highly homogenous (001) diamond film over areas more than 50
mm2. The epitaxial relationship between diamond and the Ir
substrate is diamond(001)≤Ir(001) with diamondw100x≤Irw100x. The
films have also been characterized by AFM, SEM, TEM, and Raman. As a result
of the superior thermomechanical properties of sapphire, this
heteroepitaxial system may enable wafer-size heteroepitaxial diamond growth
in the near future.
15.
Dariavach, N., Z. Z. Fang, et al. (2004). "Microtextural analysis of
lead free solder alloys." JOM 56(11): 156.
There is a thrust to develop lead free solder alloys, having better or at
least similar properties to conventional tin-lead solder alloys. Tin based
eutectic and near-eutectic compositions similar to Sn-4Ag-1Cu are most
promising alloys. However, there is still a lack of comprehensive
understanding of the microstructure of these materials, hence their
dependence on processing variable. In order to achieve best possible
properties a comprehensive physical metallurgical analysis is required. In
this direction, for alloy Sn-3.8Ag-0.7Cu, microstructural and microtextural
analysis was done using Scanning Electron Microscope (SEM) and Electron
Back-Scattered Diffraction (EBSD) technique. Composition and
crystallographic details for different phases were measured and it was found
that the intermetallics had a different composition from that of reported in
literature. Orientation of different microstructural components was found.
Misorientation relationship between different microstructural constituents
including copper substrate was found. It is found that intermetallics have a
definitive misorientation relationship with tin matrix and copper substrate.
16.
Dark, C. J., S. C. Speller, et al. (2006). "The development of
bi-epitaxial texture and high grain boundary Jcvalues in Tl-2212
films on MgO substrates." Superconductor Science & Technology
19(6): 484-492.
We have found that naturally occurring grain boundaries in
Tl2Ba2CaCu2O8 (Tl-2212) thin
films grown on MgO substrates have significantly higher critical current
values (Jcgb) than expected. In particular, films
grown on clean MgO are bi-epitaxial, containing almost exclusively 45
degrees tilt grain boundaries with Jcgb values as high
as 106 A cm-2 at 77 K. We have used high resolution
electron backscatter diffraction (EBSD) to analyse the structure of both
`natural' grain boundaries in Tl-2212 films grown on MgO substrates, and
`artificial' grain boundaries forced to form in Tl-2212 films grown on
lattice-matched bicrystal substrates such as LaAlO3.
Polycrystalline, c-axis aligned Tl-2212 films on `dirty' MgO contain diffuse
or highly dissociated grain boundaries, thus explaining their high
Jc values. Artificial grain boundaries, however, show a much more
abrupt change in orientation at the grain boundary. The bi-epitaxial 45
degrees grain boundaries are also abrupt; therefore, the high
Jcgb values suggest that the local structure or
chemistry at these grain boundaries is different from those of both
artificial and other natural grain boundaries in polycrystalline
films.
17.
Dastur, Y. N. and W. C. Leslie (1981). "Mechanism of Work-Hardening in
Hadfield Manganese Steel." Metallurgical Transactions A 12(5):
749-759.
18.
Dave, V. R., M. J. Cola, et al. (2004). "Grain Boundary Character in
Alloy 690 and Ductility-Dip Cracking Susceptibility." Welding Journal
83(1): 1-5.
A complete elucidation of the physical mechanisms responsible for
intermediate temperature ductility loss in metals (ductility dip) is
elusive. This article provides insight pertaining to ductility dip cracking
in Alloy 690, namely that the fraction and interconnectivity of low-energy
coincidence site lattice grain boundaries have a pronounced effect on
material susceptibility to ductility-dip cracking. In this work, as-received
wrought Alloy 690 is compared to Alloy 690 that was strain annealed to
achieve a different configuration of special boundaries. Hot ductility tests
are performed using a Gleeble" thermomechanical simulator. It is shown
that the intermediate temperature ductility dip is less pronounced in the
strain-annealed material, that it is shifted toward lower temperatures, and
that the on-cooling ductility recovery temperature (DRT) is higher. Scanning
electron microscope fractographic analysis is coupled with electron
backscattered diffraction (EBSD) pattern analysis to provide a preliminary
metallurgical explanation of this improvement. It is qualitatively shown
that improving the topological connectivity of these special boundaries in
Alloy 690 enhances material resistance to cracking. Although this current
study does not examine all possible factors contributing to ductility-dip
cracking (DDC), it does suggest that grain boundary character and
specifically the topological connectivity of special boundaries are
important but, previously, not widely appreciated microstructural
influencing factors in DDC.
19.
Davenport, A. J., A. Fones, et al. (2005). Crystallographic effects in the
passivation and dissolution of magnesium. 207th Meeting of the
Electrochemical Society, Quebec, Canada.
Magnesium is protected from corrosion by a nanometer-scale passive oxide
film with an inner layer of MgO adjacent to the metal. This film is
thermodynamically stable above pH 10.8, and below this value, is kinetically
stable as film growth is more facile than active dissolution of Mg.
Galvanostatic measurements have shown that the growth of the film at high pH
(where no detectable dissolution takes place) is consistent with the high
field Cabrera-Mott model rather than the point defect model. Furthermore,
the rate of film growth is affected by the crystallography of the metal
surface. This was determined on textured magnesium plate, where the kinetic
behavior on the plate surface (which has grains that are predominantly
parallel to the basal plane of the metal (0001)) is significantly different
from that on the cross section of the plate (which has predominantly
prismatic planes of the form [101õ0]). The effect of the
crystallography of the metal surface on film growth kinetics was confirmed
with microelectrochemical measurements on individual grains. Grain
orientation was determined by using electron backscattered diffraction
(EBSD). The form of the film growth kinetics and the relationship between
the growth rate and the crystallography of the metal/film interface suggests
that the rate-limiting step in film growth may be the injection of cations
into the film. Citrate is a known complexant for magnesium ions, and can be
used to etch the surface of magnesium. Examination of etched polycrystalline
surfaces with EBSD and atomic force microscopy (AFM) reveals that the basal
planes of magnesium are etched more slowly than prismatic planes. Localized
corrosion of magnesium in the presence of chloride ions takes place in the
form of hemispherical pits, or long filaments that grow with a stream of
hydrogen bubbles from the filament tip. The propagation of these filaments
also shows some dependence on the crystallography of the substrate, and the
filaments tend to change direction at grain boundaries.
20.
Davepon, B., J. W. Schultze, et al. (2003). "Crystallographic
orientation of single grains of polycrystalline titanium and their influence
on electrochemical processes." Surface and Coatings Technology
169-170: 85-90.
In electrochemical materials science, the coating of metal surfaces by oxide
films plays an important role. The preparation of anodic oxide films
strongly depends on the crystallographic orientation of the substrate grains
which can be obtained from anisotropy-micro-ellipsometry and electron back
scattering diffraction. Interference colours of the formed oxide films and
electrochemical measurements on single grains of titanium prove differences
in film thickness and electronic properties. Therefore, the rate of ion
transfer reactions (e.g. corrosion), electron transfer reactions (e.g. metal
deposition and oxygen evolution), and photo- electrochemical reactions (e.g.
laser induced reactions) differ from grain to grain. Examples are discussed
for anodic and thermal film formation, metal deposition and laser-induced
corrosion. In clear difference to the grains, twins have a much higher
activity which can be proved in cyclovoltamograms as well as with metal
deposition.
21.
Davies, G., S. Galloway, et al. (2004). Correlation between G-line
luminescence and structure of grain boundaries in electron-irradiated EFG
silicon. Design and Nature II: Comparing Design in Nature with Science and
Engineering, Rhodes, Greece, published in Design and Nature.
Edge-defined film-fed growth (EFG) is an economical method of producing
multi-crystalline silicon ribbon for solar cells. Such silicon is heavily
doped with carbon. Scanning cathodoluminescence studies of
electron-irradiated EFG silicon show that the dominant line in the
luminescence spectrum is the G-line (due to CSQj
defects). The optical behaviour of the grain boundaries in this material is
found to depend on the boundary structure, which is determined by electron
backscattered diffraction analysis. A possible explanation for the variation
in optical behaviour is suggested.
22.
Davies, G., S. Galloway, et al. (2005). "Electronic and structural
properties of grain boundaries in electron-irradiated edge-defined film-fed
growth silicon." Semiconductor Science and Technology 20(2):
171-174.
Edge-defined film-fed growth (EFG) is an economical method of producing
multicrystalline silicon ribbon for solar cells. Such silicon is heavily
doped with carbon. After electron irradiation, the dominant defect found in
this material is the G-centre, which is associated with the
CsQi defect. In this paper, the techniques of scanning
cathodoluminescence and electron backscattered diffraction pattern analysis
are used to correlate the luminescence from the G-centre with the grain
boundary structure in electron-irradiated EFG silicon. A localized
enhancement of G-centre luminescence is found near twin boundaries at
temperatures above 20 K, whereas no such enhancement is found near low-angle
grain boundaries at temperatures up to 80 K or at twin boundaries below 20
K. This behaviour may be caused by thermal ionization of excitons from traps
at the twin boundaries, and their subsequent capture at G-centres.
23.
Davies, H. and V. Randle (2002). "Single-section plane assessment in
grain boundary engineered brass." Journal of Microscopy 205(3):
253-258.
The present paper reports a comparative analysis of Σ3 (in the
coincidence site lattice notation) grain boundary types, in two grain
boundary engineered brass specimens, by use of electron backscatter
diffraction (EBSD) data coupled to the measurement of boundary traces in a
single section. Although most of the data were analysed using the new
single-section technique, an analysis of boundary plane orientations in
three dimensions was made in a subset of the data in order to validate the
single section methodology. The single-section trace analysis procedure,
coupled with EBSD, is a viable and robust tool for analysis of Σ3 grain
boundary planes. The procedure provides data which suggest that part of the
enhanced strain-to-failure in specimen B compared to specimen A is the
result of an increased proportion of mobile Σ3 boundaries, i.e. those
which are displaced from the {111} symmetrical tilt configuration.
24.
Davies, P. A. and V. Randle (2001). "Combined application of electron
backscatter diffraction and stereo-photogrammetry in fractography
studies." Journal of Microscopy 204(Pt. 1): 29-38.
The main aim of this paper is to report on recent experimental developments
that have succeeded in combining electron back-scatter diffraction (EBSD)
with stereophotogrammetry, compared with two other methods for study of
fracture surfaces, namely visual fractography analysis in the scanning
electron microscope (SEM) and EBSD directly from facets. These approaches
will be illustrated with data relating to the cleavage plane orientation
analysis in a ferritic and C-Mn steel. It is demonstrated that the combined
use of EBSD and stereophotogrammetry represents a significant advance in the
methodology for facet crystallography analysis. The results of point
counting from fractograph characterization determined that the proportions
of intergranular fracture in C-Mn and ferritic steels were 10.4% and 9.4%,
respectively. The crystallographic orientation was determined directly from
the fracture surface of a ferritic steel sample and produced an orientation
distribution with a clear trend towards the {001} plane. A
stereo-photogrammetry technique was validated using the known geometry of a
Vickers hardness indent. The technique was then successfully employed to
measure the macroscopic orientation of individual cleavage facets in the
same reference frame as the EBSD measurements. Correlating the results of
these measurements indicated that the actual crystallographic orientation of
every cleavage facet identified in the steel specimens is {001}.
25.
Davies, P. A., M. Novovic, et al. (2002). "Application of electron
backscatter diffraction (EBSD) to fracture studies of ferritic steels."
Journal of Microscopy 205(3): 278-284.
The application of electron backscatter diffraction (EBSD) to fracture
studies has provided a new method for investigating the crystallography of
fracture surfaces. The crystallographic indices of cleavage planes can be
measured both directly from the fracture surface and indirectly from
metallographic sections perpendicular to the plane of the adjoining fracture
surfaces. The results of direct individual cleavage facet plane orientation
measurements are presented for carbon–manganese (C–Mn) and
low-alloy Mn–Mo–Ni (similar to ASTM A553 type-B). Pressure
vessel steel weld metals, obtained from fracture surfaces of Charpy impact
test specimens fractured at various test temperatures and for an ultra-low
carbon steel (Fe–0.002C–0.058P) fractured at –196 °C
by impact. In addition to the direct measurement from the fracture surface,
cleavage facet orientation measurements for the ultra-low carbon steel were
complemented by the results obtained from the metallographic sections.
Fractographic observations revealed that cleavage fracture is accommodated
by a microvoid coalescence fracture micromechanism, which was induced by
decohesion of second phase particles (inclusions). The correlation between
the direct and indirect methodologies shows that the cleavage facet planes
are dominated by the {001} plane orientations, and indicated that even when
information concerning the full five degrees of freedom is inaccessible, the
cleavage facet plane could still be determined. Finally, the advantages and
disadvantages of direct orientation measurements from the fracture surface
and indirectly by a destructive sectioning technique are discussed.
26.
Davies, P., V. Randle, et al. (2002). "Triple junction distribution
profiles as assessed by electron backscatter diffraction." Journal of
Materials Science 37: 4203-4209.
The connectivity between the boundaries is very important because the defect
character of triple junctions is expected to have a significant influence on
the bulk properties of materials, particularly mechanical behaviour. The
investigation of triple junction investigations presented here indicates
that a restricted Coincidence Site Lattice (CSL) model was found to be the
most relevant and practicable for the characterisation of triple junctions
in “Grain Boundary Engineered” materials. The triple junction
character distribution was measured using the automated Electron
Back-Scatter Diffraction (EBSD) application of Crystal Orientation Mapping
(COM) for a series of thermomechanically processed copper and alpha-brass
specimens. Triple junction character statistics were determined from COM
data, automatically using a custom- built computer program, utilising the
CSL model. The alpha-brass data were then compared with a series of
previously acquired triple junction data for a series of strain-
recrystallisation copper specimens. The main aim of the investigation was to
determine the relationship between the grain boundary and triple junction
character distributions, which was found to be essentially a linear
relationship.
27.
Davies, R. and V. Randle (1996). "Secondary Processing of Electron
Basckscatter Data from an Aluminum Alloy." Materials Characterization
37: 131-141.
28.
Davies, R. and V. Randle (1997). Applications of Crystal Orientation Mapping
to Intra-grain Misorientations. Microscopy and Microanalysis, Cleveland,
Ohio, Springer.
29.
Davies, R. K. and V. Randle (1999). "Application of crystal orientation
mapping to local orientation perturbations." EPJ Applied Physics
7(No. 1): 25-32.
30.
Davies, R. K. and V. Randle (2000). "Orientation perturbations near
triple junctions in a non-cell forming aluminum-magnesium alloy."
Materials Science and Engineering A283(1-2): 251-265.
The orientation perturbation behaviour near triple junctions in a deformed
Al–3wt.%Mg alloy has been investigated using electron back-scatter
diffraction by performing line scan measurements both perpendicular and
parallel to grain boundaries within a distance of 15 mm from the triple
junction. Crystal orientation map’s were also generated to identify
local orientation perturbations and to reveal the spatial distribution of
domain boundaries. The effect of grain orientation on the degree of
perturbation and the presence of grain boundary zones are also investigated.
The orientation perturbations followed three characteristic patterns: (i)
perturbations were present near the triple junction only; (ii) perturbations
were present near the triple junction and within the grain interior and
(iii) no perturbations were displayed either near the triple junction or
within the grain interior. Enhanced zones of perturbation were also observed
near triple junctions, the frequency and magnitude of which increased with
strain. There was no apparent relationship between grain orientation and the
degree of perturbation although the results did imply that for individual
grains, perturbation levels are influenced by the crystallographic
orientation of the neighbouring grains.
31.
Davydov, A. V., L. A. Bendersky, et al. (2004). Combinatorial investigation
of structural quality of Au/Ni contacts on GaN. Second Japan-US Workshop on
Combinatorial Materials Science and Technology, Winter Park, CO, USA,
Elsevier.
A combinatorial library of Au/Ni metallizations on GaN was microstructurally
characterized by X-ray diffraction (XRD), electron back-scattered
diffraction (EBSD) and transmission electron microscopy (TEM). The array of
single- and bi-layered metal elements of systematically varying thicknesses
was deposited by electron-beam evaporation on a GaN/c-sapphire wafer. The
elements with a single layer of Au on GaN had a fiber texture with
<111> preferred growth orientation. TEM revealed a 2 nm thick
amorphous contamination layer between the Au and GaN, which prevented the
gold from being epitaxial. By contrast, nickel in both the single-layered Ni
and bi-layered Au/Ni elements formed epitaxially on the GaN with a
(111)fcc// (0001)hex, <110>fcc//<
;1120>hex orientation relation, as observed by TEM and EBSD
The Ni layer formed two types of domains related by a 60 degrees rotation
about <111>fcc, which were replicated by the Au over-layer
in the Au/Ni structures. The improved structural quality of the bi-layered
Au/Ni as compared to the single-layered Au was due to the removal of native
contamination from the GaN surface during the initial step of Ni deposition;
this promoted epitaxial growth of both metal layers. However, as the nickel
interlayer thickness was increased above 5 nm, the Au/Ni structural quality
decreased, as measured by increased deviations from the (111)fcc
(0001)hex orientation relation.
32.
Dawson, P. R., D. E. Boyce, et al. (2005). "An isoparametric piecewise
representation of the anisotropic strength of polycrystalline solids."
International Journal of Plasticity 21(2): 251-283.
A methodology for representing the anisotropic strength of polycrystalline
solids using an isoparametric mapping is presented. A four-dimensional
hypersphere in five-dimensional (deviatoric) deformation rate space is
defined using Lagrange elements for a suite of deformation rate directions
with a specified (reference) magnitude. Onto this surface are mapped values
of the flow stress required to induce plastic flow for the corresponding
values of the reference deformation rate. The flow stress values are
evaluated from a combination of experimental data and computational results
using polycrystal plasticity. The methodology is demonstrated for three
example systems: Ti–6Al–4V plate, AA5182 hot rolled plate, and
AL6XN hot rolled plate
33.
Dawson, P. R., M. P. Miller, et al. (1998). "Quantification and
Interpolation of Texture and its Gradients in Rolled Aluminum
Plate."
34.
Day, A. (1998). "Is that one grain or two?" Materials World
6(1): 8-10.
Measuring grain size is not always easy, and results can be misleading.
Paper describes the maze of old and new techniques available to size up
those grain. New techniques based on the electron microscope, such as
orientation/channeling contrast imaging and electron backscatter diffraction
(EBSD), offer useful alternatives to conventional metallographic methods.
The ability of these new methods to relate crystallography and
microstructure is extremely useful for measuring multiphase, deformed and
difficult materials. (Edited author abstract) [References: 5]
35.
Day, A. and G. Shafirstein (1996). "Assessment of local residual strain
by electron backscatter patterns and nanoindentation." Materials
Science and Technology 12(10): 873-879.
Electron back-scatter diffraction (EBSD) has been shown to be the most
appropriate technique to study the orientation and carbide morphology of
small (<0.5 mu m) regions of microstructure of high chromium white irons.
The carbides in a slightly hypo-eutectic Fe-Cr-C alloy show a distinct
texture close to 1011 whereas those in a 1.3 wt% Si commercial white iron
have a diffuse texture, with regions near to major crystal directions, i.e.,
0011, 1210, 0110, unpopulated. Using EBSD, it has been shown that the
interconnectivity of the eutectic (Cr, Fe)7C3 carbide
is less in a 1.3 wt% Si alloy compared with a low (0.1 wt%) Si alloy. This
reduced interconnectivity is consistent with the increased fracture
toughness in the as-cast condition. (10 References).
36.
Day, A. P. and T. E. Quested (1999). "A comparison of grain imaging and
measurement using horizontal orientation and colour orientation contrast
imaging, electron backscatter pattern and optical methods." Journal of
Microscopy 195(Pt. 3): 186-196.
The problems associated with the definition of a grain, grain size
measurement, and the issues associated with making one- and two-dimensional
measurements on a three-dimensional structure are discussed. The relatively
new scanning electron microscope (SEM)-based techniques of colour
orientation contrast imaging (COCI) and automated electron backscatter
pattern (EBSP) are explained and examples given. Comparisons with
conventional (horizontal) orientation contrast imaging (HOCI) in the SEM are
made. A direct comparison is made between conventional metallographic
methods and these new techniques on precisely the same region of an
interstitial free iron specimen. Both optical imaging and HOCI were found to
miss a large number of grain boundaries (7 and 12%, respectively), and to
create boundaries (approximate to 2%). COCI was found to be reliable, with
only 3% of boundaries missed. EBSP was taken to be the standard against
which the others were compared, as it unambiguously measured changes in
crystallographic orientation. Errors in the number of grain boundaries that
are detected have a considerable effect on grain size measurements, e.g.
mean linear intercept, and a follow-on effect on the modelling of mechanical
properties. New methods for increasing the acquisition speed of orientation
maps are discussed, along with examples, The combination of COCI (for grain
location) and EBSP (for orientation measurement) is promising, but requires
improvements in either imaging or image analysis to be totally
reliable.
37.
Day, A. P., A. Gholinia, et al. (2005). Characterization of nitride thin
films by electron backscatter diffraction and electron channeling contrast
imaging. 2005 Materials Research Society Fall Meeting, Boston,
Massachusetts, USA.
In this paper we describe the use of electron backscatter diffraction (EBSD)
mapping and electron channeling contrast imaging - in the scanning electron
microscope - to study tilt, atomic steps and dislocations in epitaxial GaN
thin films. We show results from epitaxial GaN thin films and from a just
coalesced epitaxial laterally overgrown GaN thin film. From our results we
deduce that EBSD may be used to measure orientation changes of the order of
0.02 iety. 22, in GaN thin films. As EBSD has a spatial resolution of a 20
nm, this means we have a powerful technique with which to quantitatively map
surface tilt. We also demonstrate that channeling contrast in electron
channeling contrast images may be used to image tilt, atomic steps and
threading dislocations in GaN thin films.
38.
de Campos, M. F., H. Goldenstein, et al. (2005). "Texture and
microtexture studies in different types of cast irons." Materials
Science and Engineering A 398(1-2): 164-170.
Drum and disk brake for trucks are important applications for cast irons. In
the design of these components the low cycle fatigue strength is a critical
attribute for material selection. It is known that fatigue strength is
closely related to microtexture and grain boundary structure. In the present
study, these two significant microstructure factors were evaluated for three
types of cast irons with the aid of a scanning electron microscope equipped
with of electron back scattered diffraction (EBSD) patterns technique.
Samples of grey cast iron, compacted graphite cast iron and nodular cast
iron were extensively studied, and the microstructure, microtexture and
grain boundary misorientation evaluated. Complementarily macrotexture
measurements were performed in X-ray diffractometer with texture goniometer
to determine the orientation texture of the nodular and compacted graphite
cast iron. Differences in the morphologies of pearlite found in those three
types of cast irons are also discussed. The microtexture was evaluated by
means of EBSD. The analysis of texture suggests random distribution of the
orientations of ferrite grains, as a consequence of the process of
production, which includes solidification followed by phase transformation.
The absence of preferential texture is attributed to the inoculation
process, where random nuclei are introduced in the melt. Phase
transformations also favors randomization and this occurs in cast irons
because solidification first gives origin to austenite with subsequent
transformation of austenite into ferrite, after cooling.
39.
de Castro, S. F., J. Gallego, et al. (2005). A Study of Temper Rolling in
Semiprocessed Electric Steel: Correlation with Taylor Factors. 60DG
Congresso Anual da Associacao Brasileira de Metalurgia e Materiais: 60th
Annual ABM International Congress, Brasil, Belo Horizonte-MG, Associacao
Brasileira de Metalurgia e Materiais.
Microhardness measurements were carried out in individual grains with the
aim of estimating the level of work hardening and, therefore, the stored
energy as a function of crystallographic orientation, as determined by EBSD
(Electron Back Scattered Diffraction). Two different conditions of a
commercial semi-processed electric steel were investigated: The original
cold-rolled and annealed material with 0.07%C, and an additional sample that
had been subjected to a decarburizing heat treatment. A reduction of 6% in
thickness was chosen to simulate the industrial step of temper rolling. The
results showed a much better correlation between stored energy and Taylor
factors than what has previously been reported in the literature. The
improvement is thought to be related to the rather small plastic deformation
during which grains should not rotate to any significant extent, and
therefore the Taylor factors could be considered to remain constant.
40.
De Hosson, J. T. M. and V. Ocelik (2003). Functionally graded materials
produced with high power lasers. Thermec' 2003, Leganés, Madrid,
Spain, Trans Tech Publications Ltd.
In this keynote paper two examples will be present of functionally graded
materials produced with high power Nd:TAG lasers. In particular the
conditions for a successful Laser Melt Injection (LMI) of SiC and WC
particles into the melt pool of Al8Si and Ti6Al4V alloys are presented. The
formation of a relatively thick aluminum oxide layer on Al melt surface was
confirmed during in-situ melting in an Environmental Scanning Electron
Microscope (ESEM) at temperatures above 900° C. This oxide layer acts as
a barrier for particle penetration but it can be dissolved in the melt at
temperatures above 1250° C and consequently it opens a window for
particles injection. The finite element analysis of the laser melting
process of Al-Si alloy leads to the conclusions that the laser scan velocity
has only a small influence on the substrate temperature distribution in the
vicinity of the laser beam and that the size of an elongated laser melt pool
(which is the best place for injection) is extremely small. This is in
contrast to the second example of particle injection in Ti-alloys in which
an extension of a melt pool size behind the laser beam serves as an
effective instrument for successful LMI of ceramic particles. Further, the
relationships between microstructure, tensile and wear properties have been
investigated for SiC/Al-Si and WC/Ti-Al-V metal matrix composite
layers.
41.
de Kerckhove, D. G., M. B. H. Breese, et al. (1998). "Detection of
small lattice strains using beam rocking on a nuclear microprobe."
Nuclear Instruments & Methods in Physics Research 136-138:
1240-1243.
42.
de Kloe, R., M. M. Nowell, et al. (2004). A systematic study of
pseudo-symmetry problems in EBSD. European Microscopy Congress 2004,
Antwerp, Belgium.
EBSD has proven to be a powerful tool for characterizing polycrystalline
microstructures. However, some crystal structures produce patterns that are
difficult to unambiguously index. A good example is a material structure
that is only slightly tetragonal. In this case, it can be very difficult to
differentiate a (010) pole from a (100) pole from an EBSD pattern. Figure 1
shows an example of two potential indexing solutions to a pattern from a
material that is only 2% tetragonal. This ambiguity can be overcome by
simply indexing the patterns as if the diffracting lattice possessed cubic
crystal symmetry. However, such an approach introduces a pseudo-symmetry in
data collected from such materials. In other materials, such ambiguities
appear only for patterns from specific orientations. This is apparent in the
orientation map for quartz shown in Figure 2 shown without any filtering to
remove ambiguities. The speckled appearance of a few of the grains shows
that the indexing software selected multiple orientation solutions to the
patterns from these grains. The pseudo-symmetry problem in these grains can
be removed by identifying the pseudo-symmetry relation and then selecting
the majority solution within the grain. These ambiguities may also occur
when trying to differentiate between phases, even when the phases have
dissimilar crystal structures [1]. Using simulated patterns, it is possible
to identify orientations for which it may be potentially difficult to obtain
unambiguous indexing solutions. The confidence index [2] is a good indicator
of ambiguity. If the confidence index has a value of 0 then an unambiguous
indexing solution cannot be found for a pattern. By tracking the confidence
index while simulating patterns throughout orientation space it is possible
to identify orientations that may exhibit the ambiguity problem. An example
is shown in Figure 3 for the zirconium oxide for two conditions. Such
figures can be generated to reflect a variety of parameters used in
automated indexing of EBSD patterns. Such factors include the solid angle,
the number of bands detected and the tolerances allowed on the interplanar
angle matching. The effect of parameters such as solid angle and those
associated with band detection can be tracked using confidence results from
simulated patterns. In this way, it is possible to optimise indexing
parameters to mitigate the pseudo-symmetry problem.
43.
de Kloe, R., M. R. Drury, et al. (2002). Determination of Activated Slip
Systems in Experimentally Deformed Olivine-Orthopyroxene Polycrystals using
EBSD. Microscopy and Microanalysis 2002, Québec City, Québec,
Canada, Cambridge University Press.
44.
de La Chapelle, S. (2001). "Cube recrystallization textures in a hot
deformed Al-Mg-Si alloy." Scripta Materialia 45(12):
1387-1391.
The formation of cube recrystallization textures has been studied on
Al-Mg-Si polycrystals deformed at 400°C by channel die compression tests
and annealed at 510°C. A cube recrystallization texture was observed on
samples presenting a very low fraction of cube volumes before and after
deformation.
45.
De Lima, N. B., C. Herrera, et al. (2006). "Texture and relationships
of orientation in duplex stainless steels." Metalurgia and Materials
62(565): 158-161.
The textures of austenite and ferrite in o duplex stainless steel UNS 531803
were investigated by X-ray and electron (EBSD) diffraction. EBSD was also
used to analyze the orientation relationship between austenite and ferrite
in the as received condition and after solution annealing treatment.
46.
De Magalhaes, M. S. and P. R. G. Brandao (2001). Texture analysis of iron
ore and sinter from electron diffraction. III Simposio Brasileiro de Minerio
de Ferro, Ouro Preto, MG, Brasil, Associacao Brasileira de Metalurgia e
Materiais.
Electron backscattering diffraction and other scanning electron microscopy
facilities (analysis of morphology and chemistry) can allow just the use of
the scanning electron microscope (SEM) to analyse the most important aspects
of iron ores and their products. Therefore, textural results from the
electron diffraction data related to backscattered electron images (BSE) and
chemical evaluation (electron microprobe - EDS) have permitted the
recognition of all analysed phases. In this method, an electron beam is
focused onto a surface of the specimen (polished section or recently
fractured/cleaved surface) tilted at an angle of 60 deg -75 deg, this tilt
increases the signal of BSE. The obtained image characterises the symmetry
corresponding to the lattice planes of the analysed mineral and it is
referred to Kikuchi pattern. This technique is known either EBSDP, EBSP or
EBSD (electron backscattering diffraction patterns). The textural analysis
has been applied as a technique of mineral identification when morphological
analysis of hematite (Fe2 O3) and magnetite
(Fe3 O4) in the SEM (BSE and secondary electrons - SE)
do not show contrast, which could define the mineralogy and, on the basis of
chemistry data, they can not be distinguished, too. As these minerals have
different crystallographic structures, the electron diffraction application
in research of iron ores and iron based materials is justified. The first
results have showed the power of the method. Afterwards, an automated system
of Kikuchi patterns analysis will provide the crystallographic orientation
mapping.
47.
De Messemaeker, J., B. Verlinden, et al. (2004). "On the strength of
boundaries in submicron IF steel." Materials Letters 58(29):
November 2004.
Samples of interstitial free (IF) steel with a fine microstructure were
produced by different amounts of strain in ECAP, followed by an annealing
treatment. The relation between the yield stress and the microstructure of
these samples was investigated. The Hall-Petch behaviour is maintained when
a dependence of the Hall-Petch slope on the boundary misorientation is taken
into account. In calculating the average misorientation, the strength of the
low angle boundaries is assumed to increase with increasing misorientation,
whereas the strength of the high angle boundaries is assumed to be
constant.
48.
De Messemaeker, J., B. Verlinden, et al. (2004). Structural Evolution of IF
Steel during Annealing after ECAP. Second Joint International Conference on
Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France,
Trans Tech Publications Ltd.
IF steel processed by equal channel angular pressing to an equivalent strain
of 9.2 via route BA was annealed for different times at 500°C
and 600°C. At both temperatures, the microstructural evolution shows
continuous recrystallization followed by grain growth, in absence of primary
recrystallization. At 600°C a slightly bimodal grain size distribution
develops.
49.
De Messemaeker, J., B. Verlinden, et al. (2004). Mechanical behavior of IF
steel processed by equal channel angular pressing. Ultrafine Grained
Materials 3 Symposium (as held at the 2003 TMS Annual Meeting), Charlotte,
North Carolina, USA, TMS.
The evolution of the yield stress and hardening rate measured in a
compression test on IF steel processed by equal channel angular pressing
(ECAP) at 473 K via route BA., is followed up to a von Mises
equivalent strain of 9.2. At the highest strain the dependence of the
mechanical behavior on strain path is established by comparison of the 4
classical routes A, C, BA, and Bc. After annealing at
773 K for 3h the recovered microstructure, showing slight grain growth, is
quantitatively analyzed by EBSD The change in yield stress and hardening
rate with respect to the as-deformed samples is discussed.
50.
de Oliveira, T. R. and F. Montheillet (2005). Dynamic Recrystalization
During Hot Deformation of Ferritic Stainlss Steels Stabilized with Niobium
and Titanium. 60DG Congresso Anual da Associacao Brasileira de Metalurgia e
Materiais: 60th Annual ABM International Congress, Brasil, Belo
Horizonte-MG, Associacao Brasileira de Metalurgia e Materiais.
The study was carried out to understand the mechanisms occurring during
dynamic recrystallization of hot deformed 11 % chromium stabilized ferritic
stainless steels and to compare the behaviour induced by various types of
stabilization. The tests were performed at 900 and 1050DGC at various
strains and with holding times after strainning. For all test conditions,
microstructures and textures were investigated by EBSD As conclusion,
niobium has a more pronounced influence on hardening than titanium during
hot deformation, which was explained to be due to solid solution
strengthening and also to the reduction or stopping of grain boundary
migration by solute drag effect. It was observed that continuous dynamic
recrystallization (CDRX) operates in all materials starting at the onset of
straining. The D2 component, {1 1 2} < 111 >, was found as the major
texture component at the steady state for the torsion tests carried along
the negative shear direction. It was likely to be formed by the combination
of straining and growth of the grains exhibiting both low stored energy and
low rotation rate of the crystallographic axes.
51.
De Souza, E. G., F. S. Candido, et al. (2003). Primary recrystallization
texture in a extra low carbon boron added steel. Anais do 58DG Congresso
Anual da Associacao Brasileira de Metalurgia e Materiais, Rio de Janeiro,
Brasil, Associacao Brasileira de Metalurgia e Materiais.
The primary recrystallization texture of an extra low carbon boron added
steel, 90% cold rolled, box annealed at 540 deg C for 1 h, was analysed in
the scanning electron microscope using the EBSD and OIM techniques. The
results indicate that a strong gamma fibre and intense {111}<-1 -1 2>
components is developed in this material. These fibre and components are
similar to those obtained in IF steels under similar processing
conditions.
52.
de Valle, J. A., M. T. Perez-Prado, et al. (2003). Microstructural Evolution
During Hot Rolling of an AZ31 Mg Alloy. Thermec' 2003, Leganés,
Madrid, Spain, Trans Tech Publications Ltd.
The microstructural evolution of an AZ31 Mg alloy during hot rolling has
been investigated using optical microscopy and texture (macro and micro)
analysis as the main characterization tools. In particular, the differences
between the microstructure obtained by unidirectional rolling (UR) and cross
rolling (CR) are studied. Significant twinning activity is observed in both
cases. Additionally, after cross rolling, a rather heterogeneous
microstructure develops, with scattered regions populated by very fine
grains. The strong basal fiber texture of the as-received material remains
present after both hot rolling schemes. The impossibility to obtain accurate
EBSD measurements within the twinned regions suggests that significant
localized deformation takes place in those areas. Thus these regions become
preferential sites for the onset of recrystallization due to the increase in
the local strain energy.
53.
Deal, A., X. Tao, et al. (2005). "EBSD geometry in the SEM: simulation
and representation." Surface and Interface Analysis 37(11):
1017-1020.
To obtain a sufficient electron backscatter diffraction (EBSD) signal in the
scanning electron microscope (SEM), the sample is highly tilted. This
significantly increases both the backscatter yield and the percentage of
electrons that are scattered in a forward direction, making them available
for detection by the phosphor screen of the EBSD camera. Unlike a
conventional Everhart-Thornley detector in SE mode, which collects electrons
of multiple trajectories via an applied voltage, the exact position of the
phosphor screen with respect to the sample determines what solid angle of
the forward scattered electrons is detected. Poor positioning of the camera
or an unfavorable working distance may result in patterns that are less than
ideal, increasing the difficulty of automated indexing or phase
identification. Accordingly, we have used a single-scattering Monte Carlo
model to simulate electron transport through tilted samples. Results of the
simulations include tracking the spatial and energy distributions of the
electrons during three phases of the process: within the interaction volume,
on exiting the sample surface, and when reaching the phosphor screen.
Subsequent analysis fosters a better understanding of the geometric
requirements for EBSD Furthermore, our graphical representation of the Monte
Carlo results is, we feel, a significant improvement over 'connect-the-dots'
figures typical of the literature, providing greater insight into the nature
of the backscatter yield from tilted samples.
54.
DeArdo, A. J., C. I. Garcia, et al. (2005). An advanced understanding of the
polygonal ferrite microstructures of if steel using image quality analysis.
Materials Science and Technology 2005, MS and T'05, Pittsburgh,
Pennsylvania, USA.
Traditionally, descriptions of microstructures have been based on
visualization. While this may lead to classification systems that permit
differentiation, it does not allow for quantification, and does not lend
itself to either developing or applying accurate structure-property
relationships. A new technique to characterize complex microstructures has
been developed in which the image quality (IQ) of the diffraction pattern
from EBSD has been used as an index distinguishing the degree of lattice
imperfection. Since austenite decomposition products formed at different
transformation temperatures have various dislocation or sub-grain boundary
densities, this technique has been used to identify, group, and quantify the
different types of ferrite that can form in HSLA and other high strength
steels. As a more generalized application, in this paper, a study of the
dislocation density variation associated with different cooling procedures
with a commercial IF steel using this IQ analysis technique will be
presented.
55.
DeArdo, A. J., C. I. Garcia, et al. (2005). "Image quality analysis: A
new method of characterizing microstructures." ISIJ International
45(2): 254-262.
Polycrystalline aggregates are comprised of three microstructural features:
grain centers, grain boundaries, and regions affected by grain boundaries.
It is these features that determine the mechanical properties, and any
advanced understanding of microstructure-property relations requires their
quantitative description. Traditionally, descriptions of microstructures
have been based on visualization, i.e., how grains appear in the optical or
scanning electron microscope (SEM). While this may lead to classification
systems that permit differentiation, it does not allow for quantification,
especially in complex microstructures, and does not lend itself to either
developing or applying structure-property relationships. The goal of this
paper is to present a new approach to the characterization of complex
microstructures, especially those found in advanced modern high strength
steels. For such steels, the new approach employs the fact that different
types of ferrite formed at different transformation temperatures have
different dislocation or sub-grain boundary densities. Hence, measuring the
degree of lattice imperfection of the grain centers of the ferrite is one
way of first identifying, then grouping, and finally quantifying, the
different types or forms of ferrite. The index chosen in this study to
distinguish the degree of lattice imperfection is the image quality (10).
Finally, as part of the new approach a procedure has been developed to
improve the accuracy of applying IQ measurements.
56.
Deb, B., A. Altay, et al. (2004). Technique for Monitoring the Etching Rate
of Alumina. Interfacial Engineering for Optical Properties III, San
Francisco, California, USA, Materials Research Society.
The effect of chemical and thermal treatments on the grains and grain
boundaries of polycrystalline α-Al2O3 has been
examined using a combination of microscopy techniques. Commercially
available alumina samples (Lucalox™) were chemically etched in
phosphoric acid at 200°C in increments of 15 min. Thermal treatments
were carried out at 1650°C before chemical treatments. Using maps
obtained by visible-light microscopy (VLM) as a guide, the same regions were
re-examined using atomic force microscopy (AFM) after subsequent treatments.
Variations in the dissolution rates of different grains and grain boundaries
could then be studied using AFM. The geometry of the grain-boundary grooves
was compared after thermal and chemical treatments. Electron backscattered
diffraction (EBSD) patterns recorded in the scanning electron microscope
(SEM) were used to obtain crystallographic orientations of the grains which
enabled variations in dissolution rates between grains to be correlated to
orientation.
57.
Decocker, R., L. Kestens, et al. (2003). Revealing a parent based structure
after transformation based on crystallographic relations. Thermec' 2003,
Leganés, Madrid, Spain, Trans Tech Publications Ltd.
An algorithm was developed to calculate the misorientation between the
different product orientations after transforming according to the
crystallographic relation of Bain and Kurdjumov-Sachs. The routine was
applied afterwards on an experimentally measured microstructure with the
intention to reconstruct the initial parent phase structure, using the
crystallographic properties of the grain boundaries.
58.
Degallaix, S. and A. Soussan (1990). "Combined Effect of
Nitrogen-Content and Grain-Size on the Flow-Stress in Type AlSl 316L-316Ln
Austenitic Stainless-Steels." Memoires et Etudes Scientifiques de la
Revue de Matallurgie 87(7-8): 443-456.
59.
Dehghan-Manshadi, A., H. Beladi, et al. (2004). Recrystallization in 304
Austenitic Stainless Steel. Second Joint International Conference on
Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France,
Trans Tech Publications Ltd.
60.
DeHoff, R. T. (1999). "Engineering of Microstructures." Materials
Research 2(3): 111-126.
Structure is at the heart of the materials science paradigm connecting
processing with properties. In the hierarchy of structures that exist in
materials microstructure offers the richest variety of structural
arrangements. This variety is often conveniently accessible, e.g., simply by
heat treatment or mechanical deformation. Exploration of the relation
between properties and microstructure serves to establish a target range of
microstructural states that will perform. In order to attain a target
microstructure it is necessary to understand what microstructures are, and
how they evolve in processing. This presentation focuses upon the set of
tools that must be combined to achieve this control: 1. Geometry,
2.Thermodynamics, 3. Kinematics, 4. Kinetics. The content of these tools is
reviewed briefly and their uses illustrated in developing an understanding
of how microstructures evolve. In this development an attempt is made to
carry the description of each microstructural process as far as possible
without making simplifying assumptions. The study of microstructures with
this rigorous point of view was termed by F.N. Rhines,
“microstructology”.
61.
Deka, D., D. S. Joseph, et al. (2006). "Crystal plasticity modeling of
deformation and creep in polycrystalline Ti-6242." Metallurgical and
Materials Transactions A 37(5): 1371-1388.
This paper develops an experimentally validated computational model based on
crystal plasticity for the analysis of two-phase α/ β Ti-6242
polycrystalline alloys. A rate-dependent elastic-crystal plasticity model is
incorporated in this model to accommodate anisotropy in material behavior
and tension-compression asymmetry inherent to this alloy. A combination of
microtesting, orientation imaging microscopy, computational simulations, and
minimization process, involving genetic algorithms, is implemented in this
study for careful characterization and calibration of the material
parameters. Size effects are considered in this analysis through a simple
scaling process. A homogenized equivalent model of the primary α with
transformed b colonies is developed for incorporation in the Ti-6242 FE
model. The polycrystalline Ti-6242 computational model incorporates accurate
phase volume fractions, as well as statistically equivalent orientation
distributions to those observed in the orientation imaging microscopy scans.
The effects of orientation, misorientations, and micro-texture distributions
are investigated through simulations by this computational model. The model
is used to simulate constant strain rate and creep tests in compression and
tension, and the results are compared with experiments. The effects of
microstructure and creep-induced load-shedding on the localization of
microstructural stresses and strains are studied for potential crack
initiation criteria.
62.
del Valle, J. A., M. Eddahbi, et al. (2004). "Comparison of the
microstructure and thermal stability of an AZ31 alloy processed by different
severe plastic deformation processing routes." JOM 56(11):
223.
The aim of this work is to compare the microstructure, the texture, as well
as the thermal stability of an AZ31 Mg alloy processed via two different
severe plastic deformation (SPD) processing techniques, namely large strain
hot rolling (LSHR) and equal channel angular pressing (ECAP). The
microstructure was characterized by optical microscopy and the texture was
measured both by X-ray diffraction (XRD) and electron backscatter
diffraction (EBSD). The processing conditions were chosen to achieve similar
strain levels using both routes. The microstructure obtained via LSHR is
finer, with average grain sizes around 3 nm, but quite heterogeneous. During
large strain hot rolling a well define basal texture develops. The sample
processed by ECAE is comparatively more homogeneous and slightly coarser,
with an average grain size of 7 mm. Simultaneously, a shear-type texture
develops. It was found that the sample processed via LSHR was prone to
heterogeneous grain growth and secondary recrystallization after annealing
at 250ion elect C for 15 h whereas the sample processed via ECAE underwent
homogeneous grain growth under the same annealing conditions. The influence
of the microstructure on the thermal stability is explored.
63.
del Valle, J. A., M. T. Perez-Prado, et al. (2005). "Deformation
Mechanisms Responsible for the High Ductility in a Mg AZ31 Alloy Analyzed by
Electron Backscattered Diffraction." Metallurgical and Materials
Transactions 36A(6): 1427-1438.
The microstructural evolution during tensile deformation of an AZ31 alloy
with grain size ranging from 17 to 40 m, at intermediate temperatures, has
been studied using electron backscattered diffraction (EBSD) and optical
microscopy (OM) as the main characterization tools. Two deformation regimes
could be distinguished. In the high-strain-rate regime, the stress exponent
was found to be about 6, and the activation energy is close to that for Mg
self-diffusion. These values are indicative of climbcontrolled creep. In the
lower strain rate range, elongations higher than 300 pct were measured. In
this range, significant dynamic grain growth takes place during the test,
and thus, the predominant deformation mechanisms have been investigated by
means of strain-rate-change tests. It was found that the stress exponent
varied during the test between 1.7 and 2.5, while the activation energy
remains close to that for grain-boundary diffusion. The EBSD analysis
revealed, additionally, the appearance of low to moderately misoriented
boundaries that tend to lay perpendicular to the tensile axis. The enhanced
ductility of this AZ31 alloy in this regime is attributed to the operation
of a sequence of deformation mechanisms. Initially, grain-boundary sliding
governs deformation; once dynamic grain growth occurs, dislocation slip
becomes gradually more important. Dislocation interaction gives rise to the
appearance of new interfaces by continuous dynamic recrystallization
(CDRX).
64.
Delannay, F., S. Godet, et al. (2003). "Microtextural study of variant
selection by EBSD in a bainitic steel containing retained austenite."
Journal De Physique IV 112(I): 309-312.
The phenomenon of variant selection in a bainitic steel containing retained
austenite was investigated. The steel was hot-rolled below the Tnr to true
strains of ε = 0.2 and ε = 0.8 in the austenite temperature
range. The orientation relationships between bainite and austenite are
expressed in Rodrigues space. A strain of 0.2 is shown to be insufficient to
induced variant selection. A hot deformation of 0.8 leads to a much smaller
number of variants being created, which are shown to be related to the slip
systems active during austenite deformation.
65.
Delannay, L., O. V. Mishin, et al. (2001). "Quantitative analysis of
grain subdivision in cold rolled aluminum." Acta Materialia
49(13): 2441-51.
A procedure is proposed for a statistical characterisation of deformed
microstructures from the data collected using Orientation Imaging Microscopy
(OIM). This procedure has been applied for a characterisation of 352 grains
in commercial purity aluminium cold-rolled to a reduction of 40%. The
results demonstrate the different behaviour of grains with different
orientations: (i) grains having orientations near the {001}<100> and
{025}<100> components develop orientation gradients over distances of
10–20 μm; (ii) grains with orientations close to the
{205}<502> component form fragments with relatively large
misorientations, and (iii) grains within the β-fibre form fragments
with relatively small misorientations. The experimental results are compared
to previous observations by transmission electron microscopy (TEM) and good
agreement is found. Finally, possible applications of the present
observations for advanced texture modelling are discussed.
66.
Delannay, L., R. E. Loge, et al. (2003). "Measurement of In-Grain
Orientation Gradients by EBSD and Comparison with Finite Element
Results." Advanced Engineering Materials 5(8): 597-600.
The electron backscatter diffraction (EBSD) technique allows rapid
orientation mapping over large sample areas. This enables the analysis of
tendencies that can only be derived from the averaged behavior of many
grains. In this communication, we present a recent study based on this
feature, in order to gather statistically relevant information about the
orientation gradients that developed within grains of a coldrolled aluminum
plate. We also check whether the orientation gradients observed can be
attributed to the interaction of adjacent grains. We rely on the finite
element (FE) technique to simulate plane strain compression of an aggregate
of 1200 grains. Twelve of these grains have an identical initial orientation
that has been selected, either close to {001}<100>, or along the
(3-fiber (i.e., {110}<112>, {123}<634>, and {112}<111>).
Every one of the 12 grains has a distinct neighborhood and follows thereby a
different deformation path. In concordance with experimental measurements,
the FE simulations lead to a larger average orientation spread within grains
oriented near {001}<100>. However, the amplitude of the orientation
spread is underestimated, whatever the initial orientation of
grains.
67.
Demeester, P., S. T. F. Grimson, et al. (2000). "Probing nitride thin
films in 3-dimensions using a variable energy electron beam." MRS
Internet Journal of Nitride Semiconductor Research 5(Suppl. 1):
6.
In this paper we illustrate the application of electron beam techniques to
the measurement of strain, defect and alloy concentrations in nitride thin
films. We present brief comparative studies of CL spectra of AlGaN and InGaN
epilayers and EBSD patterns obtained from two silicon-doped 3 µm thick
GaN epilayers grown on an on-axis (0001) sapphire substrate and a sapphire
substrate misoriented by 10° toward the m-plane (10-10).
68.
Demirel, M. C., A. P. Kuprat, et al. (2002). Large scale statistics for
computational verification of grain growth simulations with experiments.
Modeling and Numerical Simulation of Materials Behavior and Evolution.
Symposium, San Francisco, CA, USA, Materials Research Society.
It is known that by controlling microstructural development, desirable
properties of materials can be achieved. The main objective of our research
is to understand and control interface dominated material properties, and
finally, to verify experimental results with computer simulations. We have
previously showed a strong similarity between small-scale grain growth
experiments and anisotropic three-dimensional simulations obtained from the
Electron Backscattered Diffraction (EBSD) measurements. Using the same
technique, we obtained 5170-grain data from an Aluminum-film (120 mu m
thick) with a columnar grain structure. Experimentally obtained starting
microstructure and grain boundary properties are input for the
three-dimensional grain growth simulation. In the computational model,
minimization of the interface energy is the driving force for the grain
boundary motion. The computed evolved microstructure is compared with the
final experimental microstructure, after annealing at 550 degrees C.
69.
Demirel, M. C., A. P. Kuprat, et al. (2002). "Linking Experimental
Characterization and Computational Modeling of Grain Growth in
Al-Foil." Interface Science 10: 137-141.
Experimental results on grain boundary properties and grain growth obtained
using the Electron Backscattered Diffraction (EBSD) technique are compared
with the Finite Element simulation results of an Alfoil with a columnar
grain structure. The starting microstructure and grain boundary properties
are implemented as an input for the three-dimensional grain growth
simulation. In the computational model, minimization of the interface energy
is the driving force for the grain boundary motion. The computed evolved
microstructure is compared with the final experimental microstructure, after
annealing at 550◦C. Good agreement is observed between the
experimentally obtained microstructure and the simulated microstructure. The
constitutive description of the grain boundary properties was based on a
1-parameter characterization of the variation in mobility with
misorientation angle.
70.
Demirel, M. C., B. S. El-Dasher, et al. (2000). Studies on the Accuracy of
Electron Backscatter Diffraction Measurements. Electron Backscatter
Diffraction in Materials Science. A. J. Schwartz, M. Kumar and B. L. Adams.
New York, Kluwer Academic/Plenum Publishers: 65-74.
71.
Demirel, M. C., D. C. George, et al. (2003). "Bridging simulations and
experiments in microstructure evolution." Physical Review Letters
90(1).
By performing electron backscatter diffraction (EBSD) measurements, data
were obtained for 5170 grains from 19 thin aluminum foil samples with
columnar grain structure. Computational results were compared to those of
experiments. It was found that microstructural evolution in columnar
aluminum foils can be correctly modeled using anisotropic
parameters.
72.
Demura, M., K. Kishida, et al. (2004). Texture Development of Ni3Al Thin
Foils during Recrystallization and Grain Growth. Second Joint International
Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M,
Annecy, France, Trans Tech Publications Ltd.
The texture evolution of 83% cold-rolled Ni3Al foils during
recrystallization was examined through heat treatments at 600°C,
800°C, and 1000°C for 30 min. X-ray texture measurements revealed
that the texture changed from the as-rolled Goss to a transitional
complicated one by primary recrystallization and eventually returned to the
Goss texture during grain growth. The SEM-EBSD analysis revealed that the
return to the Goss texture was accompanied by the decrease of random
boundaries (RBs) and the increase of Σ1 boundaries. The preferential
growth of the Goss-oriented grains was explained by the difference in the
grain boundary energy between the RBs and Σ1, based on the observed
grain-orientation maps.
73.
Demura, M., Y. Suga, et al. (2001). "Fabrication of Ni3Al
thin foil by cold-rolling." Intermetallics 9: 157-167.
Thin foils of stoichiometric Ni3Al with thicknesses ranging from
57 to 315 mm were successfully fabricated by heavily cold-rolling without
intermediate annealing. Starting materials were produced by directional
solidification using the floating zone method. The total reduction in
thickness obtained was as much as 95.5%. This high rolling ductility is
considered to be due to the monocrystalline or near monocrystalline form of
the starting materials. X-ray pole figures showed the formation of {110}
rolling texture. This {110} texture is considered to develop mainly as a
result of compressive deformation normal to the rolling plane. The foils
recrystallized at temperatures over 1273 K had some tensile ductility (3.0
-14.6%) at room temperature in air, in contrast to the usual brittleness of
polycrystalline Ni3Al. Electron back scatter diffraction
measurements revealed that low angle and Σ3 coincidence site lattice
boundaries, which are considered to be crack-resistant, comprised 41 - 84%
of the total grain boundary area in the recrystallized foils. This large
fraction is probably a chief cause of the observed ductility. These results
demonstrate that it may be possible to utilize Ni3Al thin foils
as lightweight, high-temperature structural materials, e.g. honeycomb
structures.
74.
Deng, J. N., E. Bouzy, et al. (2005). Texture Control in Silver. Textures of
Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
We find that a severely rolled FeCo alloy has anomalous enhancement of the
rotated-cube {100}<011> texture component and a decrease of the {111}
components after annealing, which is contrast to the recrystallization
behaviors reported in traditional BCC metals and alloys. The local texture
measurements show that two kinds of grains with obviously different
orientations, i.e. {100} and {111}, are heterogeneously distributed in the
deformed specimen and the migration of high-angle grain boundaries is
observed after annealing in the disordering temperature region.
75.
Deshpande, A. R. and J. M. K. Wiezorek (2006). "Texture evolution in
equiaxed polycrystalline L10-ordered FePd during coarsening at
600 L12 C." Zeitschrift fuer Metallkunde 97(3):
304-309.
The texture evolution in equiaxed polycrystalline L10-FePd during
the coarsening regime of annealing at 600tructure) C after cold-rolling has
been investigated, using X-ray diffraction and scanning electron microscopy.
A change in dominant texture was observed. Using the nomenclature
established for texture description of face-centered cubic metals, the
texture of the L10-FePd develops from a brass-type texture into a
strong cube-type texture during coarsening. Also, a large density of special
high-angle grain boundaries emerged during coarsening, which can be
described as coherent Σ2-boundaries and are associated with (90
ependent beha 5) of the t -rotations about a common cube-axis between the
neighboring grains. The emergence of Σ-boundaries may play an
important role for previously reported abnormalities in the grain growth
kinetics. xponent n Carl Hanser Verlag.
76.
Detavernier, C. and C. Lavoie (2005). Texture in thin films. Textures of
Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
First, a brief overview is given of different experimental methods that can
be used to characterize texture (x-ray diffraction pole figure measurements
and electron backscattered diffraction), with an emphasis on the challenges
that are presented by the small grain size and limited amount of material
present in thin film samples. Second, a classification is presented of the
types of texture that have been reported for thin films, and various
terminologies are discussed (fiber texture, in-plane texture, biaxial
texture, epitaxy, epitaxial alignment and axiotaxy). Finally, several
driving forces are described that can cause texture selection and texture
evolution in thin films.
77.
Deville, S., G. Guénin, et al. (2004). "Martensitic
transformation in zirconia - Part I. Nanometer scale prediction and
measurement of transformation induced relief." Acta Materialia
52(19): 5697-5707.
We investigate by atomic force microscopy (AFM) the surface relief resulting
from martensitic tetragonal to monoclinic phase transformation induced by
low temperature autoclave aging in ceria-stabilized zirconia. AFM appears as
a very powerful tool to investigate martensite relief quantitatively and
with a great precision. The crystallographic phenomenological theory is used
to predict the expected relief induced by the transformation, for the
particular case of lattice correspondence ABC1, where tetragonal c axis
becomes the monoclinic c axis. A model for variants spatial arrangement for
this lattice correspondence is proposed and validated by the experimental
observations. An excellent agreement is found between the quantitative
calculations outputs and the experimental measurements at nanometer scale
yielded by AFM. All the observed features are explained fully quantitatively
by the calculations, with discrepancies between calculations and
quantitative experimental measurements within the measurements and
calculations precision range. In particular, the crystallographic
orientation of the transformed grains is determined from the local
characteristics of transformation induced relief. It is finally demonstrated
that the strain energy is the controlling factor of the surface
transformation induced by low temperature autoclave treatments in this
material.
78.
Devilliers, D., T. Baudin, et al. (2004). "Selective electrodeposition
of PbO2 on anodised-polycrystalline titanium."
Electrochimica Acta 49(14): 2369-2377.
Electrochemical experiments on titanium electrodes were coupled with
electron backscattered diffraction (EBSD) experiments. The substrates were
thermally treated and electropolished in order to have flat and reproducible
polycrystalline surfaces, leading to EBSD orientation mapping. Afterwards,
the samples were anodised by a galvanostatic procedure. It was shown that
electrodeposition of PbO2 from a 0.5 M
Pb(NO3)2 + 2.5M HNO3 solution occurs
selectively on the near {000l} grains, whereas lead electrodeposition occurs
on all the grains, whatever their orientation. These results are discussed,
taking into account the fact that on {0 0 0 1} grains, the oxide layers are
thinner than on other grains. It was concluded that electrodeposition is
observed locally on Ti/TiO2 electrodes for (i) cathodic
electrodeposition of metals at low overvoltage; (ii) anodic
electrodeposition of PbO2, in potentiostatic or galvanostatic
conditions.
79.
Dewobroto, N., N. Bozzolo, et al. (2004). Experimental Investigations of
Recrystallization Texture Development in Zirconium (Zr702). Second Joint
International Conference on Recrystallization and Grain Growth, ReX &
GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
80.
Dewobroto, N., N. Bozzolo, et al. (2005). Influence of Deformatio
Substructures on the Early Mechanisms of Recrystallization in Cold-Rolled
Titanium and Zirconium. Textures of Materials - ICOTOM 14, Leuven, Belgium,
Trans Tech Publications.
The mechanisms governing the very first stage of static recrystallization in
two hexagonal alloys (commercially pure titanium and low alloyed zirconium)
are investigated in this paper. Initially fully recrystallized and equiaxed
materials were cold-rolled to 80% thickness reduction and subsequently
recrystallized at 500°C for short times. High resolution EBSD maps were
acquired in a FEG-SEM before and after annealing in order to see where and
how the new grains appear. Non-oriented nucleation mechanisms are involved
in both materials, and there is a strong correlation between the local
deformation substructures and the recrystallization kinetics.
Recrystallization is extremely fast in the areas where the deformation cells
are small and highly misoriented, i.e. in the areas which underwent severe
grain fragmentation. Twinning plays an important role for that purpose in
the studied titanium sheet.
81.
Dey, S. R., A. Hazotte, et al. (2005). "Development of
Widmanstätten laths in a near-ψ TiAl alloy." Acta Materialia
53(14): 3783-3794.
Microstructures composed of Widmanstätten laths embedded in lamellar
colonies were obtained by moderate rapid cooling of a quaternary near-γ
TiAl alloy, Ti–46.8Al–1.7Cr–1.8Nb (at.%). The
morphological and crystallographic features of these microstructures were
characterized using SEM (with EBSD) and TEM. Identification of different
γ variants was done using an original approach based on automatic
analysis of Kikuchi patterns obtained by TEM in convergent beam mode.
Widmanstätten laths systematically show misorientations of ~65°
around the axis <1100>α2 with respect to
the embedding lamellar structure. The inner structure shows similarities
with the lamellar structures, i.e., multi-platelet structure with Blackburn
relationship between γ and α2 phases and {1 1 1}y habit
planes. It also presents strong differences in terms of lamellae fineness
and the amount and morphology of α2 phase. Moreover, the
Widmanstätten laths contain a lot of internal structure defects. From
the results presented, and taking into account that the 65°
misorientation between the Widmanstätten laths and the lamellar
structures is associated with a twinning system of the hexagonal phase
({1122}<1123>), we suggest a new transformation mechanism for the
development of Widmanstätten laths during cooling.
82.
Dey, S. R., E. Bouzy, et al. (2006). "EBSD characterisation of massive
γ nucleation and growth in a TiAl-based alloy." Intermetallics
14(4): 444-449.
Electron backscattered diffraction (EBSD) has been carried out to obtain
large orientation maps of massive γ (γm) structures
in a Ti–46.8Al–1.7Cr–1.8Nb (at.%) alloy.
γm grains presenting a Blackburn orientation relationship
with one of the two parent α grains were detected along several
α/α boundaries. According to previous studies, they were
identified as original γm nuclei. Along a given α/α grain
boundary, gm nuclei in relation with one α grain were always
shown to be dominant with respect to the other. Moreover, while two twin
variants are expected for this γm nucleus type, our study
pointed out the predominance of one of the two twins. These clear selection
phenomena are analysed in terms of favourable orientation relationship
between the grain boundary plane and the habit plane of γm
nucleus. An original analysis of EBSD maps pointed out that a large majority
of the γ m grains present in the microstructure can be
grouped in as large ‘twin-domains’, inherited from the growth of
these initially favoured Blackburn orientation related (OR)
γm nuclei, through a mechanism of successive twinnings.
This growth firstly occurs in the α grain having no Blackburn
orientation relationship with the original nucleus, but later generations of
γm twins can further re-enter into the original parent
α grain in Blackburn orientation relationship. Although some
misoriented or unfavourable Blackburn OR gm nuclei have also been
detected close to the grain boundaries, they were always found to be dormant
with respect to further growth. Depending upon the description on
γm grains, a mechanism of their germination and growth is
proposed.
83.
Diaz-Fuentes, M., A. Iza-Mendia, et al. (2003). "Analysis of Different
Acicular Ferrite Microstructures in Low-Carbon Steels by Electron
Backscattered Diffraction. Study of their Toughness Behavior."
Metallurgical and Materials Transactions A 34A(11):
2505-2516.
Acicular ferrite formation, promoted by the intragranular nucleation of
ferrite plates, is well known to be beneficial for achieving a good
combination of mechanical properties. However, the set of microstructures
that can be obtained during the subsequent development of the transformation
from the primary plates generated at particles can be quite complex and
depends on a certain number of variables: steel composition, temperature
range, prior austenite grain size, and particle density. In the present
work, acicular ferrite microstructures have been produced by isothermal
treatments in three different steels with different active particle types
and densities. The morphology of the obtained intragranular microstructures
has been found to depend on the steel composition, the prior austenite grain
size, and the density of particles able to promote intragranular nucleation.
Electron backscattered diffraction (EBSD) techniques have been used to
define the microstructural unit defining toughness in these types of
microstructures.
84.
Dickey, E. C., Y. M. Bagiyonoa, et al. (2000). "Preferred
crystallographic orientation relationships of nickel films deposited on
(100) cubic-zirconia substrates." Thin Solid Films 372:
37-44.
Preferred crystallographic orientation relationships between nickel films
grown on (100)cubic-zirconia substrates were studied by a variety of
electron diffraction techniques. The predominant orientation relationship
found was Ni(111)ZrO2(100); Ni <110> ZrO2 010,
while a secondary cube-on-cube orientation relationship was also observed.
Orientation imaging microscopy (OIM) shows the different orientations to be
distributed homogeneously across the substrate. The near coincident site
lattice (NCSL) theory was employed to rationalize the observed orientation
relationships from a geometrical perspective. The experimentally observed
orientations do lead to small NCSL unit cells, but not always the smallest
possible. It is also found that the choice of sublattice for calculating the
NCSL is significant in this system, since the Zr and O sublattices of
cubic-zirconia have different atomic spacings and coordination.
85.
DiDomizio, R., J. S. Marte, et al. (2006). Structure and properties of
NI-20CR produced by severe plastic deformation. 2006 TMS Annual Meeting, San
Antonio, Texas, USA.
Nanostructured and ultrafine-grained metallic systems are of interest as
structural materials because of their superior mechanical properties. This
paper will examine two severe plastic deformation (SPD) processes for
producing nanostructured and ultrafine-grained alloys: multi-axis forging
(MAP) and equal channel angular extrusion (ECAE). The two processes were
applied to a Ni-20 wt.% Cr alloy to determine the extent of grain refinement
achievable via SPD. The multi-axis forging process resulted in an equiaxed
microstructure with an average grain size of 1.3 micron. The ECAE process
resulted in a heavily dislocated structure with shear bands and sub-grain
sizes of approximately 100-300 nm. Heat treatment of the ECAE alloys
resulted in dislocation-free structures and substantial grain growth. The
evolution of micro-texture was examined by electron backscatter diffraction.
Low levels of micro-texture were observed after heat treatment. Tensile
tests were performed on the SPD processed Ni-20Cr. A significant increase in
tensile strength was observed in SPD material compared to its conventionally
processed counterpart.
86.
Dijkstra, A. H., M. R. Drury, et al. (2002). "On the role of melt-rock
reaction in mantle shear zone formation in the Othris Peridotite Massif
(Greece)." Journal of Structural Geology 24(9):
1431-1450.
A 1-km-wide peridotite mylonite shear zone is exposed in the Othris
peridotite massif in central Greece. The mylonites contain lenses of
relatively coarse olivine crystals, which are interpreted as remnants of the
tectonite microstructure in the adjacent wall rocks. Microstructure and
texture analysis using light and SEM microscopy suggests that the dominant
deformation mechanism in the tectonites was dislocation creep, whereas the
deformation in the mylonites was probably controlled by grain-size sensitive
(GSS) creep in fine-grained (<50 μm) bands consisting of a mixture
of olivine and orthopyroxene. The development of the fine-grained material
in the mylonites can be explained by a melt-present reaction taking place in
the tectonite protolith. This reaction led to the replacement of
orthopyroxene porphyroclasts by fine-grained olivine and orthopyroxene.
Tectonites adjacent to the mylonite zone preserve evidence for this reaction
in the form of rims of fine-grained olivine and orthopyroxene around
orthopyroxene porphyroclasts. This study illustrates the significance of
rheological weakening of oceanic mantle lithosphere as a result of a change
from dislocation to GSS creep
87.
Dillen, H., C. Xhoffer, et al. (2000). "Application of Microbeam
Techniques in the Steel-Industry." Mikrochimica Acta 132(2-4):
323-335.
88.
Dillen, R., A. D. Vyt, et al. (2004). "From Substrate to Coating:
Micro- and Surface Analysis Techniques for the Development of Steel
Products." Microchimica Acta 145: 29-39.
For the development of ultra high strength steel and hyperdrawable steel
grades precipitates had to be tailored at the nanoscale. Microbeam
techniques helped to reach a superior quality of metallic coatings and a
superb adhesion to the steel substrate. In this paper the use of
micro-analytical techniques in steel product development is
illustrated.
89.
Dingley, D. (2004). "Progressive steps in the development of electron
backscatter diffraction and orientation imaging microscopy." Journal of
Microscopy 213(Pt 3): 214-224.
Ten years ago electron backscatter diffraction (EBSD) became available to a
wider group active in materials research. This paper highlights some of the
more significant developments in camera technology and software developments
that have arisen since then. The use of slow-scan charge couple device
cameras for phase identification and rapid determination of orientation
image micrographs is reviewed. The current limiting spatial resolution of
the technique is shown to be less than 10 nm. A procedure for improving
lattice spacing measurement by utilizing the full resolution of the camera
is described with experimental measurements on silicon and nickel showing
relative errors of plus/minus 3%. An investigation of partially
recrystallized aluminium shows how the recrystallized fraction can be
extracted with confidence but that the mapping of substructure in the highly
deformed regions is questionable. Phase identification is described for
complex cases in which the phase data tabulated in standard databases do not
correspond to what is observed in the EBSD patterns. Phase mapping in a
complex mineral in which chemical data and EBSD data are collected
simultaneously is shown to be improved by recording both the chemical and
the EBSD data into computer memory and proceeding with the phase
discrimination and orientation measurement in off-line analysis.
90.
Dingley, D. J. (1981). "A Comparison of Diffraction Techniques for the
SEM." Scanning Electron Microscopy IV(P4): 273-286.
91.
Dingley, D. J. (1984). "Diffraction from Sub-micron areas using
electron backscattering in a scanning electron-microscope." Scanning
Electron Microscopy 11(P2): 569-575.
92.
Dingley, D. J. (1984). "On-line determination of crystal orientation
and texture determination in an SEM." Proceedings of the Royal
Microscopic Society 19: 74-75.
93.
Dingley, D. J. (1988). On Line Microtexture Determination Using Backscatter
Kikuchi Diffraction in a Scanning Electron Microscope. ICOTOM 8, Santa Fe,
New Mexico, The Metallurgical Society.
94.
Dingley, D. J. (1989). "Orientation measurements using EBSD."
Institute of Physics Conference Series, EMAG, 89: 473-476.
95.
Dingley, D. J. (1990). "Developments in online crystal orientation
determination." Institute of Physics Conference Series(98):
473-476.
96.
Dingley, D. J. (1991). Backscattering in the SEM. Institute of Physics
Conference Series (EMAG).
97.
Dingley, D. J. (1994). Advances in strain measurement using
electron-backscatter diffraction in the SEM. Fifty-Second Annual Meeting
Microscopy Society of America/Twenty-Ninth Annual Meeting Microbeam Analysis
Society, New Orleans, LA, San Fancisco Press, Inc.
The technique of electron back scatter diffraction, EBSD is well established
for measurement of crystal orientation in bulk polycrystalline samples.
Several papers have been published describing the application of method for
strain measurement. In the study presented, analysis was carried out on
digitized television images of the diffraction patterns imaged live on a
phosphors screen. [References: 7]
98.
Dingley, D. J. (1994). Electron backscatter diffraction. Procedures in
Electron Microscopy. A. W. Robards and A. J. Wilson. New York, John Wiley
and Sons.
99.
Dingley, D. J. (1995). Electron Backscatter Diffraction: a New Tool for
Material Characterisation. Microscopy and Microanalysis, Jones and Begall
Publishing.
100.
Dingley, D. J. (1995). Further Advances in Orientation Imaging Microscopy.
Microscopy and Microanalysis, Jones and Begall Publishing.
101.
Dingley, D. J. (1996). An Investigation of Partially Recrystallised Steel
Using Electron Backscatter Diffraction. 6th Asia Pacific Conference on
Electron Microscopy.
102.
Dingley, D. J. (1996). Method and Apparatus for Determining Crystallographic
Characteristics. USA, TexSEM Laboratories, Inc., Provo, Utah:
11.
An apparatus for detemining crystallographic characteristices of a specimen
having at least one crystal includes an electron beam generator, a beam
deflector for adjusting the tilt and azimuth angles of the electron beam
relative to the specimen, a stage for holding the specimen, an image
collection system for obtaining the plurality of dark field images, a data
store, and a processor for processing the dark field images to identify a
plurality of crystal lattice planes associated with the crystals. The dark
field images are obtained under different electron beam tilt and azimuth
deflection conditions. The bright pixels in each dark field image are
identified and utilized to determine the spatial location and orientation of
the crystal lattice planes and the crystals themselves. An orientation image
is produced that represents the orientaiton of the crystals within the
specimen.
103.
Dingley, D. J. (1998). Automated Crystallography Using Electron
Backscattering Patterns. 14th International Congress on Electron Microscopy,
Cancun, Mexico.
104.
Dingley, D. J. (1998). Automated Materials Characterization in Electron
Microscopy. 14th International Congress on Electron Microscopy, Cancun,
Mexico.
105.
Dingley, D. J. (1998). "Observation of recovered recrystallized and
deformation structures in partially recystallized steel using orientation
imaging microscopy."
106.
Dingley, D. J. (1999). Crystal Phase and Orientation Mapping in
Metallurgical and Mineralogical Materials. Eighth International Conference
on Instrumental Analysis, Beijing, China.
107.
Dingley, D. J. (1999). Investigation of Low Symmetry Crystals Using Electron
Backscatter Diffraction. Microscopy and Microanalysis, Portland, Oregon,
Springer-Verlag.
108.
Dingley, D. J. (1999). Orientation Relationships Between Crystals in
Non-cubic Systems. International Conference on Textures and Physical
Properties of Rocks, Gottingen, Germany.
109.
Dingley, D. J. (2000). T he development of automated diffraction in scanning
and transmission electron microscopy. Electron backscatter diffraction in
materials science. A. J. Schwartz, M. Kumar and B. L. Adams. New York,
Kluwer Academic/Plenum Publishers: 1-18.
110.
Dingley, D. J. and D. Dingley (1996). A Novel Method for Measurement and
Mapping of Crystal Orientations in Polycrystalline Materials in the
Transmission Electron Microscope. 6th Asia Pacific Conference on Electron
Microscopy.
111.
Dingley, D. J. and D. P. Field (1995). "Electron Backscatter
Diffraction and Orientation Imaging Microscopy, An Overview." Journal
of Materials Science and Technology.
112.
Dingley, D. J. and D. P. Field (1995). An Experimental Investigation of
Grain Boundaries, the Coincident Site Lattice Theory and their Relevance to
Material Properties. Structural Materials Engineering Applications,
Structure Through Design. Cambridge, UK, Institute of Metals Publishing,
Cambridge University Press: 23-42.
A new technique has been employed to search for coincident site lattice
(CSL) orientation relationships in OFC cooper (copper?) and a nickel base
alloy. The technique, known as orientation imaging microscopy, is based on
automated detection and indexing of electron backscatter diffraction
patterns obtained from a sample mounted in a scanning electron microscope.
No evidence was found to indicate that CSL orientations, apart from twins
and their higher orders, existed in either material at a level above what is
expected in a purely random structure. The technique was also used to
investigate the relationship between grain orientation and the fracture path
taken by a crack in the nickel base alloy. The crack was observed to be
intergranular and avoided all twin boundaries.
113.
Dingley, D. J. and D. P. Field (1996). "Investigation of Aluminum Thin
Films using Electron Backscatter Diffraction and the New Technique of
Orientation Imaging Microscopy." Materials Research Society Symposium
Proceedings(403): 197-206.
114.
Dingley, D. J. and D. P. Field (1997). "Electron backscatter
diffraction and orientation imaging microscopy." Materials Science and
Technology 13(1): 69-78.
An overview of electron backscatter diffraction is presented in which
experimental procedures are reviewed together with a basic theoretical
description of the mechanism of pattern generation. Manual and automated
indexing procedures are described. The new technique of orientation imaging
microscopy is presented, with examples from recrystallised Al-Mg alloy,
deformed superplastic material, and fractured nickel base alloy.
115.
Dingley, D. J. and G. Burns (1983). "Diffraction studies of laser
annealed polysilicon." Institute of Physics Conference Series(68):
433-436.
116.
Dingley, D. J. and K. Baba-Kishi (1986). Use of electron backscatter
diffraction patterns for determination of crystal symmetry elements.
Scanning Electron Microscopy, Chicago, SEM Inc.
117.
Dingley, D. J. and K. Baba-Kishi (1990). "Electron Backscatter
Diffraction in the Scanning Electron Microscope." Microscopy and
Analysis(17).
118.
Dingley, D. J. and K. Kunze (1994). Orientation Imaging Microscopy and
Serial Sectioning. ICEM 13-Paris.
119.
Dingley, D. J. and M. M. Nowell (2004). "The Use of Electron
Backscatter Diffraction for the Investigation of Nano Crystalline Materials
and the Move Towards Orientation Imaging in the TEM." Microchimica Acta
147: 157-165.
Electron backscatter diffraction is shown to have a spatial resolution
between 5 nm and 10 nm and is well suited for the investigation of nano
crystalline materials. A study of texture and mesotexture in copper
Damascene interconnect lines is used as an illustration. Samples were
prepared by electro deposition from baths of different compositions and
under various power cycles. The resulting grain structures were visually
smaller than the 0.3 micron interconnect line width. However, if twin
boundaries were considered as substructure rather than true grain
boundaries, the effective grain size become larger than the line width. The
bath composition affected the 111 texture component from times 5 random to
26 times random whereas different power cycles affected the texture much
less. For structures with a grain size smaller than 20 nm a new transmission
electron microscope technique has been developed. Automated examination of a
sequence of dark field images collected from a selected area lead to the
reconstruction of a diffraction pattern for each pixel within the area.
These patterns are indexed automatically, permitting crystal orientation as
a function of spatial positioning to be mapped. The resulting orientation
information is equivalent to that obtained using electron backscatter
patterns. The practical resolution limit of this technique approaches 1 to 2
nanometers.
120.
Dingley, D. J. and N. Razavizadeh (1981). "The Use of Kossel
Diffraction in the SEM for Precision Crystallographic Studies in Metallurgy,
Mineralogy and Semiconductor-Materials." Scanning Electron
Microscopy(P4): 287-294.
121.
Dingley, D. J. and S. Biggin (1973). "A comparison of the Kossel X-ray
diffraction technique with the electron channelling technique."
Conference on Scanning Electron Microscopy: Systems and
Applications.
There are three alternative techniques for obtaining crystallographic
information from small volumes of bulk specimens in a scanning microscope.
Kossel X-ray diffraction (KDP), selected area electron channelling (SACP),
and electron back scattering (EBSP). Some background notes on KDPs are
presented and then the experimental technique is compared with the SACP
technique. It is shown that KDP is a simple technique to apply, that the
patterns provide more precise information, and that the definition of the
patterns is less dependent on specimen perfection than is that of SACPs. (4
References).
122.
Dingley, D. J. and S. I. Wright (1999). The Combined Use of EBSD and EDS
Analysis in the Mapping of Crystal Orientation and Phase in Mineralogical
Samples. International Conference on Textures and Physical Properties of
Rocks, Gottingen, Germany.
123.
Dingley, D. J. and S. I. Wright (2000). Automated Crystallography in
Electron Microscopy. 7th Asia-Pacific Electron Microscopy - Physical
Sciences, Singapore, Times Printers Pte. Ltd.
124.
Dingley, D. J. and V. Randle (1992). "Microtexture determination by
electron back-scatter diffraction." Journal of Materials Science
27(17): 4545-4566.
A computer procedure for online analysis of electron back scattering
patterns (EBSP) has been developed. An experimental EBSP is
computer-recorded and displayed on a computer monitor. The user identifies
the positions of at least two bands in the EBSP with a cursor. Based on this
input the computer calculates possible crystallographic orientations. The
corresponding EBSPs are simulated and superimposed on the experimental EBSP.
The correct crystallographic orientation is determined from a comparison
between the experimental and simulated EBSPs. Typically, the analysis takes
10-30 seconds per pattern. Advantages of the procedure are that it can be
applied for any crystal symmetry, that it requires no knowledge about
electron diffraction maps, that it can be used for EBSPs with relatively low
contrast, and that the indexing is very precise. For relative orientation
measurements the accuracy is found to be within the range 0.05 degrees -0.20
degrees, whereas, for repeated measurements of a given grain after complete
remounting of sample and EBSP equipment, it
125.
Dingley, D. J. and V. Randle (1992). "Review. Microtexture
determination by electron back-scatter diffraction." Journal of
Materials Science 27: 4545-4566.
126.
Dingley, D. J., A. Day, et al. (1990). Application of Microtexture
Determination using EBSD to Non Cubic Crystals. ICOTOM 9, Avignon, France,
Published in Textures and Microstructures, 14-18.
127.
Dingley, D. J., A. J. Wilkinson, et al. (1990). "Strain Measurement
Using EBSP." Proc. XIIth Int. Conf. on Electron Microscopy:
402-403.
128.
Dingley, D. J., C. Alabaster, et al. (1990). "Phase Identification
Using Backscatter Kikuchi Diffraction in the Scanning
Electron-Microscope." Institute of Physics Conference Series(98):
451-454.
129.
Dingley, D. J., C. Harper, et al. (1982). "Line Profiling of Kossel
X-Ray Diffraction Lines in a SEM Using an Energy-Dispersive X-Ray
Detector." Institute of Physics Conference Series(61): 63-66.
130.
Dingley, D. J., C. Preece, et al. (1993). "Orientation Changes During
Sintering of Nickel." Institute of Physics Conference Series(138):
373-376.
131.
Dingley, D. J., D. P. Field, et al. (1997). Crystallographic Imaging in the
SEM, Phase, Orientation and Deformation Mapping. Japanese Microscopy
Society.
132.
Dingley, D. J., G. Meaden, et al. (2006). "High-resolution elastic
strain measurement from electron backscatter diffraction patterns: New
levels of sensitivity." Ultramicroscopy 106(4-5):
307-313.
In this paper, we demonstrate that the shift between similar features in two
electron backscatter diffraction (EBSD) patterns can be measured using
cross-correlation based methods to $POM@0.05 pixels. For a scintillator
screen positioned to capture the usual large solid angle employed in EBSD
orientation mapping this shift corresponds to only similar to 8.5µ
L@10-5 rad at the pattern centre. For wide-angled EBSD patterns,
the variation in the entire strain and rotation tensor can be determined
from single patterns. Repeated measurements of small rotations applied to a
single-crystal sample, determined using the shifts at four widely separated
parts of the EBSD patterns, showed a standard deviation of 1.3µ
L@10-4 averaged over components of the displacement gradient
tensor. Variations in strains and rotations were measured across the
interface in a cross-sectioned S1-xGex epilayer on a
Si substrate. Expansion of the epilayer close to the section surface is
accommodated by tensile strains and lattice curvature that extend a
considerable distance into the substrate. Smaller and more localised shear
strains are observed close to the substrate-layer interface. EBSD provides
an impressive and unique combination of high strain sensitivity, high
spatial resolution and ease of use.
133.
Dingley, D. J., J. Alderman, et al. (1987). "Online Analysis of
Electron Back Scatter Diffraction Patterns.1. Texture Analysis of Zone
Refined Polysilicon." Scanning Microscopy 1(2): 451-456.
134.
Dingley, D. J., K. Baba-Kishi, et al. (1994). Atlas of Backscatter Kikuchi
Diffraction Patterns. Bristol and Philadelphia, Institute of Physics
Publishing.
135.
Dingley, D. J., L. Baker, et al. (1981). "EBSPs from
semiconductor-materials." Institute of Physics Conference Series(61):
541-544.
Venables et al. (1981) have shown that good electron backscattering patterns
(EBSPs) can be obtained in these circumstances and so the authors have added
this technique to complement that of Kossel diffraction. It has been shown
that Venables' technique for obtaining EBSPs in the SEM can be used in a
routine fashion for investigating semiconductor materials and that the
pattern can be obtained under a wide range of experimental conditions. The
minimum selected area for this technique, using an SEM of average vacuum,
appears to be about 1000 AA and the minimum practical voltage approximately
10 kV. (4 References)
136.
Dingley, D. J., M. Longdon, et al. (1987). "On-line Analysis of
Electron Backscatter Diffraction Patterns, Texture Analysis of
Polysilicon." Scanning Electron Microscopy 1(2):
451-456.
137.
Dingley, D. J., M. Tiner, et al. (2002). Application of Orientation Imaging
Microscopy in the TEM to studies of nano-crystalline materials. Microscopy
and Microanalysis 2002, Québec City, Québec, Canada, Cambridge
University Press.
138.
Dingley, D. J., N. Gravestock, et al. (1987). "Texture determination in
deformed rocks using backscatter Kikuchi diffraction." Institute of
Physics Conference Series(No. 90: Chapter 5).
139.
Dingley, D. J., R. MacKenzie, et al. (1989). "Application of BKD for
Phase Identification of Crystals and Strain Measurement in Materials."
Microbeam Analysis: 435-441.
140.
Dingley, D. J., S. I. Wright, et al. (1998). Crystallographic mapping in
scanning and transmission electron microscopy with application to
semiconductor materials. Electron Microscopy of Semiconducting Materials and
ULSI Devices, San Francisco, CA, USA, Materials Research Society.
The two sister techniques, Electron Backscatter Diffraction and Orientation
Imaging Microscopy which operate in a scanning electron microscope, are well
established tools for the characterization of polycrystalline materials.
Experiment has shown that the limiting resolution for mapping is the order
of 0.1 microns. The basic techniques have been extended to include
multiphase mapping. Whereas it has been possible to distinguish between
phases of different crystal systems easily, it has not been possible to
distinguish between phases that differ in lattice parameter by less than 5%.
An equivalent transmission electron microscope procedure has been developed.
The technique couples standard hollow cone microscopy procedures with dark
field microscopy. All possible dark field images that can be produced by
tilting the electron beam are scanned to detect under what settings each
crystal is brought into a diffracting condition. Subsequent analysis permits
determination of both crystal phase and orientation. (4 References).
141.
Dingley, D. J., S. I. Wright, et al. (2002). "Fast Orientation Imaging
Microscopy." Microscopy Today May/June 2002(#02-3):
10-14.
142.
Dingley, D. J., T. Boal, et al. (1993). "The Orientation of
Grain-Boundaries in Annealed Copper." Institute of Physics Conference
Series(138): 377-380.
143.
Dobatkin, S. V., A. A. Kuznetsov, et al. (2006). ECA pressing up to failure
of oxygen-free copper: Structure, properties, effect of the route. 2006 TMS
Annual Meeting, San Antonio, Texas, USA.
Structure and mechanical properties of oxygen-free copper depending on the
route of ECA pressing at very high strain were studied. Deformation was
performed at an angle of 90° between the channels. The maximum number of
passes upon deformation by routes A, Bc, and C was N=25. The TEM
and EBSD examinations revealed the appearance of subgrains and submicron
grains. The average size of structure elements was similar to 200 nm (by
TEM) and 230-460 nm (by EBSD). The fraction of high-angle boundaries at N=25
is between 69 and 77%. DSC analysis showed that the least equilibrium
structure, including the structure of grain boundaries, is observed upon ECA
pressing by route Bc All strength characteristics have the maximum values
after route Bc. Elongation decreases at the early stage of ECA
pressing, but then it is stabilized or grow. An increase in plasticity is
most pronounced upon deformation by route Bc after sufficiently
high strain.
144.
Dobatkin, S. V., V. I. Kopylov, et al. (2004). Formation of High-Angle Grain
Boundaries in Iron upon Cold Deformation by Equal-Channel Angular Pressing.
Second Joint International Conference on Recrystallization and Grain Growth,
ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
At present, the possibility of the formation of high-angle grain boundaries
upon severe cold deformation, in particular, equal-channel angular (ECA)
pressing, is reliably proved. The structure formation upon multi-cycle ECA
pressing substantially depends on the route determining the shear plane in
the sample upon repeated passes. The route is defined by the rotation of the
sample around its axis upon the multi-cycle ECA pressing. There are four
main routes: route A, in which the sample is deformed by many passes without
any rotations; route Ba, in which the sample is rotated by ± 90°;
route Bc, in which the sample is sequentially rotated in the same direction
by 90°; and route C, in which the sample is rotated by 180° about
its axis before each subsequent pass. By the methods of SEM, TEM and EBSD
analysis, it was shown that the fraction of high-angle boundaries in
α-Fe upon cold ECA pressing with an angle of 90° between the
channels and N=4 depends on the deformation route and increases according to
the route sequence: Ba-C-Bc.
145.
Dobranszky, J., P. J. Szabo, et al. (2003). Energy-dispersive spectroscopy
and electron backscatter diffraction analysis of isothermally aged SAF 2507
type superduplex stainless steel. ICXOM XVII, 17th International Congress on
X-Ray Optics and Microanalysis, Mont Blanc, France.
Due to thermal effects, several precipitation and segregation processes are
known in duplex stainless steels. These microstructural changes influence
both of the original phases, but in different ways. Isothermal ageing in a
large range of temperature was performed on SAF 2507 type steel. The
temperature range was 300-1000 °C, the ageing time was between 100 s and
24 h. This paper discusses the results of ageing at 900°C.
Microstructural changes were investigated by electron microscopy,
energy-dispersive spectroscopy and electron backscattered diffraction
analysis. This technique allowed the determination of the microstructure of
the secondary austenite and S phase and their mutual orientation properties.
Beside this, thermoelectric power measurements were also performed, which
gave information about the kinetics of the precipitation process. Results
showed that Σ-phase precipitation started right after 200 s in the
case of annealed steel, and faster than 100 s in the cold-rolled state.
After 5000 s, the δ-ferrite disappeared. Chemical composition of
Σ phase was independent of the ageing time. A small decrease in nickel
content was observed with a slight increase of Cr content. Small amounts
ofξ phase had also been observed on the ferrite-ferrite boundaries, but
later they changed into Σ phase. Similarly to Σ phase, ξ
phase showed significant phosphorus enrichment. During ageing, small chrome
nitride precipitates developed, which amount increased in time, and some
vanadium could be measured in them. The orientation relationship between
austenite and Σ phase deviated from Nenno-orientationship by about 24
degree, and seems to form a (110) dbl vertical bar (310) relationship, which
was characteristic right from the beginning of the process, and remains more
or less constant.
146.
Doherty, R. D. (1997). "Recrystallization and Texture." Progress
in Materials Science 42(1-4): 39-58.
147.
Doherty, R. D. (2003). "Comments on 'Mechanical deformation of
dendrites by fluid flow during the solidification of undercooled
melts'." Scripta Materialia 49(12): 1219-1222.
The claim of no evidence for dendrite arm bending in conventional
solidification made in the paper by Dragnevski et al. is disputed by the
apparently ubiquitous observation of small (1-10) misorientations that are
found in as-cast grains during conventional solidification. Investigation of
this phenomenon by misorientation measurements by EBSD is
recommended.
148.
Doherty, R. D., I. Samajdar, et al. (1992). "Orientation imaging
microscopy - Application to the study of cube recrystallization texture in
aluminum." Scripta Metallurgica et Materialia 27(11):
1459-1464.
As recently shown by Heijlen et al., the study of local orientations by the
use of Backscattered Kikuchi Diffraction (BKD), sometimes called Electron
Back-Scattering Patterns (EBSP), in a scanning electron microscope, is able
to give very clear insight into the origin of recrystallization textures
(RT). One method of analysis is to present the results as a map of the
orientations on an equivalent grid to that used for the generation of the
data, but at a magnified scale. This map is a novel micrograph of the region
studied. Such maps provide a new metallographic method that is called
Orientation Imaging Microscopy, OIM. The purpose of the present note is to
present some initial studies by OIM of material previously characterised by
manual BKD methods. The results clearly show that the strong
recrystallization texture arises by the much more frequent formation of new
cube grains, the oriented nucleation mechanism, and not by the growth to
larger sizes, the oriented growth mechanism, at least for sample A. Although
this had been previously established by manual methods of BKD, the automated
OIM methods allow much less subjectivity in the chosen data. In addition,
the fully detailed orientation imaging micrographs establish the same
conclusions much more soundly. [References: 11]
149.
Doherty, R. D., K. Kashyap, et al. (1993). "Direct Observation of the
Development of Recrystallization Texture in Commmercial Purity
Aluminum." Acta Metallurgica et Materialia 41(10):
3029-3053.
150.
Doherty, R. D., L.-C. Chen, et al. (1998). "Cube recrystallization
texture - experimental results and modeling." Materials Science and
Engineering A257: 18-36.
151.
Doherty, R., E. Hoffman, et al. (2004). Abnormal Grain Coarsening and Its
Possible Relationship with Particle Limited Normal Grain Coarsening. Second
Joint International Conference on Recrystallization and Grain Growth, ReX
& GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
The prior literature on abnormal grain coarsening (AGC) at low volume
fractions (f) of stable second phase particles in high purity Al alloys is
reviewed and reanalyzed in the light of developments in modeling particle
inhibition of grain boundary migration. With the usual assumptions (i) of
incoherent particles that retain their shape on contact with the grain
boundaries and (ii) that all the grain boundaries are equally mobile, it
appears impossible to account for process of AGC. Normal grain coarsening
(NGC) is shown to be less inhibited by the particles than is AGC.This idea
is explored using a new but simple model of particle inhibition by curvature
removal. The curvature of the smallest grains is always larger than that of
the larger grains. Two possible hypotheses to overcome this difficulty are
proposed: First, the possible change of shape of particles on slowly moving
grain boundaries, of grains with near 14 neighbors should, after a small
increment of NGC, promote AGC at low values of the volume fraction f. The
second hypothesis involves the observed high density of immobile, low angle
grain boundaries (LAGBs) found in recent experiments on high purity Al-Fe-Si
alloys cast with very coarse grain sizes. These alloys undergo rapid AGC
even at higher values of f (>0.01). These LAGBs are expected to inhibit
the shrinkage of many of the small grains, whose loss is the fundamental
mechanism of NGC.
152.
Dollar, M. and S. Gorczyca (1982). "The Effect of Grain-Size on
Polycrystal Hardening." Scripta Metallurgica 16(8):
901-906.
153.
Dollar, M., I. M. Bernstein, et al. (1988). "Influence of Deformation
Substructure on Flow and Fracture of Fully Pearlitic Steel." Acta
Metallurgica 36(2): 311-320.
154.
Donet, S., F. Weiss, et al. (2003). "Reel-to-Reel MOCVD for YBCO Coated
Conductor." IEEE Transactions On Applied Superconductivity
13(2): 2524-2527.
A reel-to reel MOCVD system has been developed for a fast and economic
process to get high quality YBCO coated conductor tapes. Several oxides
buffer layer sequences (based on YSZ, CeO2,
Y2O3...) were then grown epitaxially on two kinds of
tape. Effective stacking for MOCVD reported here are
YSZ/Y2O3/YBCO and YSZ/CeO2/YBCO,
respectively, on oxidized Ni RABiTS microalloys (0,1% W) and on SS/YSZ
(IBAD) tapes. First, EBSD and AFM techniques have been used to characterize
the substrates. Superconducting YBCO films were fully characterized by SEM,
XRD and AC susceptibility measurements Epitaxial growth was depicted with a
strong in-plane and out-of plane texture: FWHM of YBCO j-scans were
8.5º on Ni tape and 9º on IBAD Hastelloy tapes. High performances
were also measured by AC susceptibility, with Jc values of 0.6 MA
/cm2 at 77 K (0 T) on Ni tape and close to 1 MA /cm2 on IBAD
substrates, with a sharp transition (δTc < 0.4 K) and a
Tconset at 90 K. Deposition of 2 meter buffered YSZ and
CeO2/YBCO films have also been performed showing good in-plane
alignment (φ-scan YSZ: FWHM = 11º) with a tape velocity set at 4
m/h.
155.
Donet, S., P. Chaudouet, et al. (2004). "Electron backscattered Kikuchi
diffraction technique: for a better understanding of epitaxial
superconducting film growth on buffered Ni (RABiTS) tapes." physica
status Solidi C 1(7): 1957-1960.
A reel-to-reel MOCVD system has been designed to synthesize high quality
YBCO coated tapes on Ni RABiTS (Rolling Assisted Biaxially Textured
Substrates). Special buffer layer stackings have been deposited to improve
the quality of the superconductor. Several buffer layers architectures rose
in dense YBCO films with a similar texture, but fluctuations in critical
current densities (Jc) were measured. Therefore, a more accurate and
detailed measurement method such as Electron Backscattered Kikuchi
Diffraction (BKD) has been used to assess the crystalline quality of the
stackings. The studied sequence here was NiW /NiO /YSZ /CeO2 /YBCO. The
grain and the subgrain structure as well as their size and disorientation
have been analysed for each layer. First on Ni tape, secondly on the
protecting NiO (200) buffer layer, then on the following CeO2 (200) film.
Finally, unpublished BKD diagrams of the subsequent YBCO (00l) films have
been reported here. The grain evolution has been successfully studied
showing the buffer layer effect on the grain growth. In this work we
highlight the correlation between the misorientation of the grains (inducing
NiO (111) growth and cracks) and the grain boundary morphology (size,
grooves).
156.
Dong, C., H. He, et al. (2004). "Effect of grain orientation on the
nitriding rate of a nickel-based superalloy Inconel 690." Cailiao
Rechuli Xuebao (Transactions of Materials and Heat Treatment) (China)
25(6): 79-82.
Inconel 690, a nickel-based superalloy, was nitrided by means of plasma
nitriding. SEM, XRD and Electron Backscatter Diffraction (EBSD) were
employed to characterize the nitrided layer. The results indicate that a low
temperature plasma nitriding of Inconel 690 produces a supersaturated
nitrogen solid solution in austenite (γN phase). The
thickness of the γN layer is different between grains with
different grain orientation. The γN layer grows faster in
the grains with small t<100> than in the grains with large
t<100>, θ<100> being the smallest
angle between the <100> direction and growth direction of the nitrided
layer. Furthermore, the thickness of the γN layer shows an
approximate linear relationship with θ<100>.
157.
Dong, Q. and Z. Wenzheng (2005). "Measurement and characterization of
the surface relief in a duplex stainless steel." Acta Metallurgica
Sinica (China) 41(9): 897-904.
The surface relief, especially the double-tilt surface relief, associated
with diffusion controlled phase transformations in some alloys, has not been
well understood so far. A bottleneck is the absence of a strict and
systematic measurement method. The present paper introduced a new
measurement method based on the EBSD and AFM technology. Various
crystallographic features were quantitatively determined by this method,
including the orientation relationship (OR), the orientation of the habit
plane (IO), the displacement vector inducing the surface relief and the
maximum relief angle. The OR and IO were consistently in agreement with the
calculated results from the O-line method. However understanding of the
displacement vector and unusual large relief angle needs further
study.
158.
Dongshan, Z., Q. Wenbang, et al. (2004). "Polythermal projection of
primary Al-Cu-Fe icosahedral quasicrystal phase and the related crystal
phase." Acta Metallurgica Sinica (China) 40(1): 14-19.
A series of Al-Cu-Fe alloys with compositions of
Al48-60Cu33-50Fe0-10 was prepared and the
phase constituents in these alloys quenched from various temperatures were
identified by using XRD, SEM, EDXS and EBSD attached to SEM, and TEM
(including HRTEM). Compared with the polythermal projection proposed by
Gayle et al, a main amendment is to divide the previous β-region into
β + phi two regions. A new ternary reaction is the quasiperitectic at
U8: L + β to IQC+ phi. EDXS reveals that the composition of
f phase with Ni2A3 structure is in
Al47.3-50.6Cu45.4-48.1Fe4.5-5.δ2, and
its center composition is
Al47.9Cu47.1Fe5.0.
159.
Dorkel, S., D. Schuster, et al. (1993). "Optimized Hough transform
applied to EBS patterns." Journal of Computer Assisted Microscopy
5(2): 151-157.
The Hough transform (HT) is a powerful method to detect straight lines in
images. However in the standard HT from a binary image, the number of points
on a line is not related to the total line length across the image. We
consider the congestion of the line, i.e., the number of points on a line
divided by the length of the line segment bounded by the image frame. The
method introduced in this paper, modifies the content of the Hough
accumulator as if the input image has been modified on each of its pixels.
This modification depends on two factors: the congestion of the line and on
the global saturation of the image. The method is automatically adapted to
situations with many or few points, and is available for binary and gray
level images. Consequently, the procedure allows the reduction of the number
of lines usually detected as a result of noise in the image. The result
gives an easy way to extract maxima from the accumulator, which is actually
one of the most delicate parts of the HT computation. This method has been
applied to EBS Patterns, in which the pairs of lines characterize the
orientation of the crystal lattice. (Author abstract) [References:
7]
160.
Dorner, D. and S. Zaefferer (2004). Microstructure and texture of shear
bands in cold rolled silicon steel single crystals of Goss orientation. 2nd
International Conference on Texture and Anisotropy of Polycrystals (ITAP 2),
Metz, France, Balaban Publishers; Scitec Publications.
An initially Goss-oriented ({110}<001> preferred crystal orientation)
FeSi single crystal was cold rolled up to 89 % reduction in thickness. The
microstructure and texture of shear bands, which develop at strains higher
than 70 %, were investigated by the EBSD (electron backscatter diffraction)
technique. The texture components within and outside of the shear bands are
the two symmetrical {111}<112> orientations and the {110}<001>
orientation. We conclude that crystallographic slip is the deformation
mechanism that is active both within and outside of the shear bands.
161.
Dorner, D., L. Lahn, et al. (2004). Investigation of the Primary
Recrystallisation Microstructure of Cold Rolled and Annealed Fe 3% Si Single
Crystals with Goss Orientation. Second Joint International Conference on
Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France,
Trans Tech Publications Ltd.
A silicon steel single crystal with {110}<001> Goss orientation was
cold rolled up to 89% thickness reduction and subsequently annealed. The
evolution of the macroscopic cold rolling texture was investigated by x-ray
diffraction. Local orientation relationships and the microstructure around
and within Goss grains of deformed and annealed samples were analysed using
the electron backscatter diffraction (EBSD) technique. During cold rolling a
texture consisting of two strong {111}<112> components and a minor
{110}<001> Goss component develops. After primary recrystallisation
the texture is characterized by a strong Goss component. Goss-oriented
grains that remain after high deformation are considered to be the origin
for the primary recrystallisation texture.
162.
Dorner, D., L. Lahn, et al. (2005). Survival of Goss grains during cold
rolling of a silicon steel single crystal. Textures of Materials - ICOTOM
14, Leuven, Belgium, Trans Tech Publications.
A silicon steel single crystal with initial Goss orientation, i.e. the
{110}<001> orientation, was cold rolled up to 89 % thickness
reduction. Most of the crystal volume rotates into the two symmetrical
equivalent {111}<112> orientations. However, a weak Goss component is
still present after high strain, although the Goss orientation is
mechanically instable under plane strain loading. Two types of Goss-oriented
crystal volumes are found in the highly deformed material. We suggest that
their origin is different. The Goss-oriented regions that are observed
within shear bands form during the cold rolling process. In contrast, those
Goss-oriented crystal volumes that are found inside of microbands survive
the cold rolling.
163.
Dorner, D., L. Lahn, et al. (2006). "Overview of Microstructure and
Microtexture Development in Grain-oriented Silicon Steel." Journal of
Magnetism and Magnetic Materials 304(2): 183-186.
This paper outlines the development of the microstructure and microtexture
of grain-oriented silicon steel during the industrial production process. In
particular the evolution of the Goss orientation was studied in industrial
material as well as in single crystal experiments.
164.
dos Santos, C. M. L., C. S. C. Viana, et al. (2003). Microstructural and
microtextural analyses of a Cu-Al-Ni shape memory alloy single crystal.
Anais do 58DG Congresso Anual da Associacao Brasileira de Metalurgia e
Materiais, Rio de Janeiro, Brasil, Associacao Brasileira de Metalurgia e
Materiais.
The use of Shape Memory Alloys (SMAs) in actuators represent a great
evolution in the aerospace industry in the last years. This technology has
been applied in several devices with great advantages, mainly
thermal-sensor-actuators. Many alloys that present the Shape Memory Effect
(SME) have been developed in the last years, mainly those composed of Ni-Ti
and Cu-Al, to be commercialized. The study of a single crystal Cu-Al-Ni SMA
using the EBSD technique, allows the characterization of the microstructure
of the phases in that it says respect to the orientation assumed for the
crystalline structure in each one of the phases, before and after the
transformation. The results of the analysis for EDS do not have a correction
with the compositions presented in recent bibliographies, being necessary an
another technique for a better evaluation.
165.
dos Santos, J. F., C. M. GarzÓn, et al. (2004). "Improvement of
the cavitation erosion resistance of an AISI 304L austenitic stainless steel
by high temperature gas nitriding." Materials Science and Engineering A
382: 378-386.
An AISI 304L austenitic stainless steel was high temperature gas nitrided in
N2+Ar atmospheres under N2 partial pressures up to
0.10MPa at 1423K for 21.6 ks. Nitrogen contents at the surface up to 0.48
wt.% and case depths up to 1mm were obtained. All the samples showed fully
austenitic microstructures free of precipitates. Solution treated AISI 304L
as well as nitrided samples were tested in distilled water in a vibratory
cavitation erosion (CE) equipment. Characterization of the test specimens
was made by optical microscopy, electron back scattering diffraction coupled
to a scanning electron microscope (EBSD–SEM), X-ray diffraction (XRD),
wavelength dispersive spectroscopy (WDS) microanalysis and depth-sensing
indentation tests. All the samples had almost the same mean grain diameter,
~80µm, similar mesotexture and microtexture, though the nitrogen
contents differed. The nitrided samples exhibited much better cavitation
erosion resistance and the erosion rate was reduced by almost 8.5 times.
Increasing the N2 partial pressure increased the nitrogen content
at the surface, leading to an increase in the incubation period for damage
and a decrease in the erosion rate.
166.
Dou, S. X., S. P. Lau, et al. (2003). "Effects of varying mechanical
deformations on the relationship between mesotexture and current percolation
in (Bi,
Pb)2Sr2Ca2Cu3O10/Ag
superconductor tapes." Superconductor Science and Technology
16(8): 885-892.
In this work, effects of varying mechanical deformations on the relationship
between mesotexture and current percolation in (Bi,
Pb)2Sr2Ca2Cu3O10+x(Bi2223)
tapes are investigated. Electron backscattered diffraction analysis
demonstrates that the mesotexture distribution characteristics influence
critical current density (Jc) as results of the processing
variations. The disorientation angle distribution dependence of
Jc is also discussed using current percolation theory. The
results show that improving the mesotexture distribution in central region
of Bi2223 tapes through optimization of the mechanical deformation
processing can significantly increase Jc.
167.
Drake, A. and S. H. Vale (1995). "Development of an electron
backscatter diffraction and microtexture measurement system." Institute
of Physics Conference Series 147: 137-140.
Microtexture and boundary characteristics have been analyzed in a
comparative study of post-deformation tensile specimens of a
superplastically processed Al-10Mg-0.1Zr alloy using electron backscatter
pattern methods in the scanning electron microscope. Interactive methods
were employed to capture nearest-neighbor (sub) grain diffraction patterns
and the data were subsequently computer analyzed to produce information on
the character of the misorientation between neighboring crystals. The data
from this study are used to determine whether grain boundary character is a
microstructural feature responsible for the distinctly different tensile
behavior observed in material processed according to two different
thermomechanical processing schedules. (9 References).
168.
Dravid, V. P., E. C. Dickey, et al. (1998). Towards (predictive)
structure-property relationships for heterophase interfaces in oxides.
Boundaries & Interfaces in Materials: The David A.Smith Symposium
Proceedings of the TMS Fall Meeting, Minerals, Metals & Materials Soc
(TMS), Warrendale, PA, USA. p.
Several advanced TEM techniques have been utilized to probe the atomic scale
details of structure, local chemistry and bonding of interfaces in
directionally solidified eutectic (DSE) of NiO-ZrO2 (ss). The
three-dimensional residual stress tensor for NiO-ZrO2 (ss) DSE was directly
determined using x-ray diffraction measurements. Crack trajectories induced
by indentation were followed by electron backscattered diffraction (EBSD) in
an SEM. Several general trends in interface structure-crack propagation
behavior seem to emerge from our collective analysis. Oxide-oxide DSEs are
characterized by strong electrostatic bonding across the heterophase
interfaces mediated by a common oxygen plane. The strong interfacial bonding
is manifested in the large residual stresses in the composites which are
both spatially and crystallographically anisotropic. Crack propagation
trajectories appear to be influenced by micro-scale features such as
residual stresses and microstructural imperfections. It is argued that while
dominant microstructural features which seem to dictate crack trajectories
are microscale, the origin and interdependence of atomic scale features and
events are intimately connected to the larger length-scale phenomena. Thus,
the results reinforce the notion that all microstructural length-scales are
of significance in macroscale properties and phenomena in materials in
general, and internal interfaces, in particular. (Author abstract)
[References: 13]
169.
Drawin, S., P. Petit, et al. (2005). "Microstructural Properties of
Nb-Si Alloys Investigated Using EBSD at Large and Small Scale."
Metallurgical and Materials Transactions A 36A(3): 497-505.
Texture and crystallographic orientation relationships in arc-melted
hypoeutectic and hypereutectic binary Nb-Si alloys are investigated.
Electron backscattered diffraction (EBSD) is used here in conventional
conditions, i.e. at relatively high spatial resolution (<1µm) for
~400 x 400 µm fields, as well as on very large fields (1.1 x 1.1 mm),
at lower resolution, to get a stitistical overview of the microstructure. In
as-cast Ni-16Si and Ni-22Si alloys (compositions are in at. pct),
[001]Nb3Si is found parallel to the local thermal gradient, with
Nb3Si + Nb eutectic cells, giving rise to a microstructure
similar to that obtained by directional solidification. In Nb-22Si alloy,
the following orientation relationships between poles of metallic and
silicide phases have been found: (111)Nb // (111)Nb3Si
(as cast), (011)Nb //
(011)α-Nb5Si3, and (111)Nb
// (100)α-Nb5Si3 (heat treated at 1500°C, 75
hours).
170.
Drezet, J.-M. and S. Mokadem (2006). " Marangoni convection and
fragmentation in laser treatment." Materials Science Forum 508:
257-262.
Epitaxial laser metal forming (E-LMF) consists in impinging a jet of
metallic powder onto a molten pool formed by controlled laser heating and
thereby, generating epitaxially a single crystal deposit onto a single
crystal substrate. It is a near net-shape process for rapid prototyping or
repair engineering of single crystal high pressure/high temperature gas
turbines blades. Single crystal repair using E-LMF requires controlled
solidification conditions in order to prevent the nucleation and growth of
crystals ahead of the columnar dendritic front, i.e., to ensure epitaxial
growth and to avoid the columnar to equiaxed transition. A major limitation
to the process lies in the formation of stray grains which can originate
either from heterogeneous nucleation ahead of the solidification front or
from remelting of dendrite arms due to local solute enriched liquid flow,
i.e fragmentation. To study this last aspect, heat and fluid flow modelling
is required to establish the relationship between process parameters such as
laser power, beam diameter and scanning speed, and the local solidification
conditions plus the fluid flow in the vicinity of the mushy zone. Surface
tension driven convection known as the Marangoni effect needs to be included
in the model owing to its large influence on the development of eddies and
on the shape of the liquid pool. The 3D model implemented in the FE software
calcosoft(R) is used to compute the fluid convection within the liquid pool
and to assess the risk of fragmentation using a criterion based on the local
velocity field and thermal gradient. The computed results are compared with
EBSD maps of laser traces carried out at EPF-Lausanne in re-melting
experiments.
171.
Driver, J. H. (1995). "Structural evolution during recrystallisation:
Problems in nucleation and growth." Journal de Physique IV 5(3):
19-28.
This review describes some recent experimental results concerning the
microstructural and texture evolutions during primary recrystallisation of
metallic alloys. The mechanisms which, by their influence on the kinetics of
local events, control the orientations of the new recrystallised grains, are
examined in order to improve our understanding of recrystallisation texture
formation. The use of new techniques such as EBSD (Electron Back-Scattered
Diffraction in a SEM) provides new perspectives for this old problem. In
particular, it is now possible to quantitatively characterise the
microstructure of the deformed state in terms of the local orientations
related to the inhomogeneities of plastic deformation. The importance of
these microtextures for the early stages of nucleation and growth is
underlined by recent recrystallisation studies on steels and aluminium
alloys. (24 References).
172.
Driver, J. H. (2003). "SEMS and MAPS: recent developments in
microstructure mapping." Revue de Metallurgie, Cahiers d'Informations
Techniques 100(5): 551-559.
Recent developments in Scanning Electron Microscopy (SEM) are reviewed
paying particular attention to the modern tendency to determine quantitative
data in the form of microstructure maps: of chemical composition (EDS and
WDS), of crystal orientation (EBSD) and of the deformation
(microextensometry). The maps are then used to provide complete,
quantitative microstructural analyses in terms of the size, orientation and
composition distributions. In this context the new SEM-FEGs have an
important role to play.
173.
Driver, J. H. and J. C. Glez (2003). "Substructure development in hot
plane strain compressed Al-1%Mn crystals." Acta Materialia
51(10): 2989-3003.
Hot PSC (channel-die) tests have been carried out to large strains (1.5) on
3 orientations of Al-1%Mn crystals, Bs{110} <112>, S{123}<412>
and U{110} <11-0>, using a wide range of temperatures and strain rates
(or Zener-Hollomon parameter Z). The deformation substructures are
characterised by EBSD orientation mapping in terms of sub-grain sizes
δ and sub-grain misorientations and their frequency distributions over
large areas. The sub-grain sizes respect the linear relation between
1/δ and lnZ but with significant orientation dependency. The largest
sub-grains are found in the Bs orientation at all Z and the smallest in the
S orientation at high strain rates. Sub-grain misorientations increase
rapidly with strain to 3 or 4° then approximately stabilise after 0.5 or
1. Some high angle boundaries (< 10Simulatio) are formed with frequencies
about 10-2 to 10-3. Many of the size effects can be
attributed to an enhanced rate of sub-boundary generation in the case of the
unstable grain orientations.
174.
Driver, J. H., D. Juul Jensen, et al. (1994). "Large Strain Deformation
Structures in Aluminum Crystals with Rolling Texture Orientations."
Acta Metallurgica et Materialia 42(9): 3015-3114.
Four single crystal orientations of high purity aluminium have been deformed
in channel die compression up to strains of ~ 1 to correlate the dislocation
substructures, in single and polycrystals with the slip system distribution.
Three orientations are close to the stable rolling texture components of fcc
metals: (110)[112], (112)[111], and (112) [174] and one is very unstable
(121) [311]. The substructures are characterized on the longitudinal section
over a wide range of scales by optical microscopy. TEM and SEM with EBSD.
Low energy dislocation matrix structures composed of cells, cell blocks,
dense dislocation walls and first generation microbands are observed in all
orientations in agreement with the microstructures of rolled polycrystals.
The S (213) [142] and C (112)[111]orientations also develop narrow bands of
localized glide associated with relatively high local misorientations. The S
orientation exhibits characteristic S-shaped band structures of first
generation microbands sheared on {111} planes whereas the C orientation
forms non-crystallographic shear bands. These two orientations can be
considered stable in terms of average texture but unstable in terms of
microstructure.
175.
Driver, J. H., Z. Jasienski, et al. (2003). "Shear band microtexture
formation in twinned face centred cubic single crystals." Materials
Science and Engineering A 359(1-2): 178-191.
The formation of brass-type shear bands (SB) in twinned microstructures of
medium and low stacking fault energy (SFE) metal single crystals (copper,
copper-2 wt.% aluminium and silver), with initial orientation
{112}<111> has been investigated after channel-die deformation at 77
and 293 K. The microstructures and local orientations were characterised
over a wide range of scales by convergent beam electron diffraction in a
transmission electron microscope, electron backscattered diffraction in a
scanning electron microscope and optical metallography. For all metals it is
shown that slip initially causes a general rotation to D(4 4 11) 11 11 8-,
which is then followed by partial twinning to the D/supT/(26 26 5) 5-5-52
orientation. Subsequent shear banding of the unstable, layered, twin
structure is responsible for the development of the strong Goss
{110}<100> orientation within the bands. A minor group of components
is observed near {114}<221>, arising from the near primary matrix
orientation. The intensity of mechanical twinning, and therefore, the
relative amounts of primary matrix and twinned material, influences the SB
internal microstructure. Alloys with low SFE such as Cu-2 wt.% Al deformed
at 77 K twin almost completely whereas Cu at 77 K and Ag at 293 K retain
significant quantities of (re-oriented) matrix and hence a relatively strong
secondary microtexture component within the brass-type bands. Copyright 2003
Elsevier Science B.V. All rights reserved.
176.
Du, Y., B. Gu, et al. (2004). "ZnO well-faceted fibers with periodic
junctions." Journal of Physical Chemistry B 108(52):
19901-19903.
ZnO well-faceted microfibers with periodic junctions were prepared by an
evaporation and deposition process. The junctions with spacings of 5-30
µm presented concavo-concave morphologies, and the spacings could be
changed with the growth conditions. The anisotropic growth mechanism was
investigated by X-ray diffraction (XRD), energy-dispersive X-ray (EDX)
analysis, scanning electron microscopy (SEM), and electron backscatter
diffraction (EBSD). The photoluminescence (PL) and PL microscopy studies
showed the structure-related optical character and that the well-faceted and
modulated fibers could serve as microscale waveguides and emit enhanced
green lights at the junctions under UV excitation. These functional
structures should make possible the creation of microscale light-emitting
arrays as well as bar codes used in biotechnology and electronics.
177.
Duan, J., Q. Cao, et al. (2006). "Preparation and characterization of
rectangular tin dioxide microtubes." Journal of Crystal Growth
289(1): 164-167.
Rutile phase SnO2 microtubes were successfully synthesized using
a thermal evaporation method at 1550 °C. The products were characterized
by X-ray diffraction, scanning electron microscopy and micro-Raman
scattering. The microtubes are as long as about 1 mm with almost perfect
rectangular cross-section. They possess a large cavity channel of about 30
μm in width and four smooth side surfaces. The side surfaces of
SnO2 microtubes are (1 1 0) and (1 1 0) planes, while their tube
axes are [0 0 1]. The possible formation mechanism of the rectangular
SnO2 microtubes is presented.
178.
Duckham, A., O. Engler, et al. (2002). "Moderation of the
recrystallization texture by nucleation at copper-type shear bands in
Al-1Mg." Acta Materialia 50(11): 2881-2893.
The critical dependency of copper type shear band formation on deformation
variables in Al-1Mg has been described (Acta mater., 49 (2001) 2739). The
influence of copper type shear bands on recrystallization behaviour during
post-deformation annealing in Al-1Mg is now discussed. Local orientation
measurements and orientation images of grains nucleating at shear bands have
been made using the electron back-scatter diffraction (EBSD) technique. Bulk
recrystallization texture is investigated from X-ray diffraction (XRD)
measurements. Shear bands are shown to be potent nucleation sites during
annealing and a weak, almost random, texture associated with nucleation at
shear bands has been inferred. Most significantly, shear band formation is
found to have a pronounced moderating influence on the strength of the
potentially dominant cube component of the recrystallization
texture.
179.
Dudarev, S. L., P. Rez, et al. (1995). "Theory of Electron
Backscattering from Crystals." Physical Review B 51(6):
3397-3412.
180.
Dueber, O., H. J. Christ, et al. (2006). "Characterizing the
microstructure of multiphase materials using EBSD." Praktische
Metallographie 43(2).
The EBSD technique is a valuable aid in characterizing microstructures. In
this work, it was employed to prepare microstructural images of a duplex
steel and discriminate between grain boundaries and phase boundaries, which
is not readily possible by using conventional etching techniques. This was
intended to determine stereological parameters or detect the spatial
microstructural configuration. The method is not limited to the duplex steel
which was presented, but is generally applicable to all two-phase or
multi-phase materials. The stereological parameters obtained, which are in
Tab. 2, served as input values to a model for a microstructure based
simulation of the growth of microstructurally short cracks in the duplex
steel under examination. Such a model can be helpful, for example, in
determining a configuration of the stereological parameters which is ideal
for a large resistance to crack propagation which allows to infer
indications about how to conduct optimum processes in alloy manufacture and
thermal treatment. Furthermore, in another work, the stereological
parameters were used to determine the obstructing effect of various boundary
types on the propagation of cracks. In addition, the orientation data from
EBSD measurements were successfully used to determine the spatial position
of slip planes, which allows to draw conclusions regarding the mechanisms
accountable for the propagation of cracks.
181.
Duggan, B. J., K. Lucke, et al. (1993). "On the Origin of Cube Texture
in Copper." Acta Metallurgica et Materialia 41(6):
1921-1927.
182.
Duggan, B. J., K. T. Lam, et al. (2003). Increasing desirable
recrystallization texture in IF steel by controlled rolling. Thermec' 2003,
Leganés, Madrid, Spain, Trans Tech Publications Ltd.
A flat {111} <hkl> texture of high intensity in IF steels following
the final anneal produces good drawability, and this is usually derived from
a fairly random hot band material. In the first part of this work,
conventional hot band was subjected to a cold roll-anneal-cold roll-final
anneal procedure in which the total reduction was 80% (i.e. gage control)
but in combinations of, for example, 70%+10% or 10%+70%. The purpose was to
find whether final rolling of essentially a {111} <hkl> (g) texture
enhanced the intensity of {111} <hkl> in the final annealed
conditions. Also the effects of whether the material was fully
recrystallized, partially recrystallized, or merely recovered after the
first annealing was investigated. The results are encouraging in that {111}
<hkl> could be increased when the texture before final cold rolling
and annealing had a high γ and low {hkl} <110> (α) fibre.
An explanation for this is provided based on Deformation Band (DB) theory.
The second part of the work concerned warm rolling of the hot band in the
α phase region, using a single pass reduction of 75%. This was either
annealed and cold rolled or just cold rolled to 80% reduction followed by a
standard recrystallization treatment. The results show the greatest
intensity of {111} <hkl> to be formed when the metal was cold rolled
without intermediate annealing. Global textures were measured using X-rays,
and the SEM techniques of EBSP and OIM coupled with conventional TEM and
STEM were used for local texture and microstructure investigations.
183.
Duggan, B. J., M. Z. Quadir, et al. (2005). Origin of the Deformation
Microstructure in IF Steel After Medium Cold Rolling Reductions. Textures of
Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
In this paper TEM work on the formation of dislocation meshes, cells,
microbands and shear bands is summarized. Following this the results of a
sequential rolling experiment in which the development of microstructure is
followed from the strain free to 50% rolling condition. Crystals behave
according to three generic types. Grains with an orientation close to
α, deform homogenously without much rotation. Grains close to
{111}<110> are also stable, and can have either α or γ
microstructure. Others seem to be able to deform homogenously up to a
certain strain, hence resembling α grains, and then rotate to γ,
forming typical g microstructures.
184.
Duggan, B. J., Y. Y. Tse, et al. (1999). A geometrical theory for
{111}<hkl> recrystallization texture formation in cold rolled IF
steel. Twelfth International Conference on Textures of Materials (ICOTOM
12), McGill University, Montreal, Canada, NRC Research Press.
185.
Duggan, B. J., Y. Y. Tse, et al. (2002). Mechanisms of Recrystallization in
Cold and Warm Rolled Low Carbon Steel and IF Steel. ICOTOM 13, Seoul, Korea,
Trans Tech Publications Inc.
Strain localization is inevitable during the rolling process, and this
manifests itself most clearly in ferrite by the formation of shear bands and
deformation and transition bands. Nucleation of recrystallisation is
strongly associated with these microstructures, and it is clear that
nucleation is a process of subgrain growth out of these features. In this
work it is shown that the Y fiber component of the rolling texture is most
prone to strain localization, and that the rotation of materials in the
shear bands and deformation bands is around<111> //ND, which gives
rise to the {111}<hkl> rolling texture. For shear band and deformation
band nuclei to dominate the final texture, it is necessary to break the
recrystallisation process into two stages, nucleation by growth of
subgrains, and "impingement growth" of strings of small grains
allowing invasion of all other material. The impingement growth provides, in
effect, a super-nucleus, and these comprise strings of {111}<hkl>
recrystallised material in cold and warm rolled IF steel, and also in a low
carbon steel alloy suitable for box annealing.
186.
Dunst, D. and H. Mecking (1996). "Analysis of Experimental and
Theoretical Rolling Textures of 2-Phase Titanium-Alloys." Zeitschrift
fur Metallkunde 87(6): 498-507.
187.
Dupont, M. L., T. Baudin, et al. (1996). "Evolution of Texture and
Microstructure of Gamma/Alpha(2) Biphase Titanium as Function of
Heat-Treatments." Journal de Physique IV 6(C2): 235-240.
188.
Dussieux, A., P. Gouton, et al. (2004). "Study of plastic deformation
modes in zirconium by color image analysis." Journal of Materials
Processing Technology 153-154: 281-287.
Twinning, as a deformation mode, is a complement to slip. This paper deals
with the study from a qualitative point of view, as well as from a
quantitative one. Besides techniques widely used in materials science
studies such as electron backscattered diffraction (EBSD) or X-ray
diffraction (XRD), colour image analysis technique are presented here. Its
results manage to confirm or complete the ones obtained, thanks to others
methods.
189.
Dvorak, J., P. Kral, et al. (2004). "Creep processes in pure aluminium
processed by ECAP technique." JOM 56(11): 216.
Creep tests were conducted on pure aluminum processed by ECAP at
temperatures 423-523K and a 10-25MPa. Specimens were examined by
transmission and scanning electron microscopy equiped with an EBSD facility.
The amount of grain boundary sliding was experimentally determined. Based on
the results. It is suggested that creep of the ECAPed aluminium occurs by
diffusion-controlled movement of dislocations and by grain boundary sliding.
The coexistence of a dislocation climbing process and grain boundary sliding
may explain the observed decrease of the creep resistance with increasing
number of ECAP passes. Since high-angle grain boundaries are necessary in
order to achieve gram boundary sliding, an increase in the fraction of
high-angle boundaries with increasing number of ECAP passes will essentially
lead to an increasing contribution of sliding to the total creep strain as
it was observed experimentally.
190.
Dzubinsky, M., Z. Husain, et al. (2004). "Comparison of
recrystallisation kinetics determined by stress relaxation, double hit,
optical metallography and EBSD approaches." Materials Characterization
52(2): 93-102.
A comparison of the recrystallisation kinetics determined by stress
relaxation (SR), double-hit (DH), optical metallography and scanning
electron microscope/electron backscattered diffraction (SEM/EBSD) mapping
experimental approaches has been conducted. Two different types of steel
were used as experimental material: C-Mn and interstitial-free (IF). Tests
were carried out in the austenitic region for C-Mn steel and just above the
Ar1 temperature for IF steel. Both steels were investigated in
static and postdynamic recrystallisation (SRx and PDRx, respectively)
regions. The work indicates that some differences exist between the results
given by these methods. The biggest correction to the experimental results
in the SRx region has to be performed on the "raw data" obtained
by the SR method. The SR method, owing to its continually applied stress,
tends to accelerate the recrystallisation kinetics. The estimation of the
recrystallised fraction in the PDRx region by the DH test gives even higher
error because of dynamic changes of microstructure during the second hit.
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