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98 records found
1.
Abart, R., K. Kunze, et al. (2004). "Silicon and oxygen self diffusion
in enstatite polycrystals: the Milke et al. (2001) rim growth experiments
revisited." Contributions to Mineralogy and Petrology 147:
633-646.
2.
Abe, T., R. Kondou, et al. (2003). "Evaluation of 3-dimensional plastic
strain of grains in polycrystalline copper during tension by EBSD method and
digital image processing." Nippon Kikai Gakkai Ronbunshu, A Hen
(Transactions of the Japan Society of Mechanical Engineers, Part A)
69(6): 972-979.
A method of evaluation of six components of grain strain in polycrystalline
metal was proposed. In the present method, the electron backscattered
diffraction (EBSD) technique and the digital image processing were
efficiently combined. Four components of grain strain,
εx, εy, εz and
gxy were evaluated based on the change in average
aspect ratio of the number of pixels inside the grain which was obtained by
an optical microscope and digital image analysis, where xy-plane is set on
the specimen surface and z-axis is directed perpendicularly to the surface.
The other two components, γyz, γzx, were
calculated by taking into consideration the restriction of plastic
deformation of each grain which was derived on the assumption that the
plastic deformation occurred by crystallographic slipping on a single set of
slip plane. An angle of the slip planes was 3-dimensionally identified by
observation of the slip line by a scanning electron microscope and EBSD
technique. Grain strain of polycrystalline copper during tension was
evaluated by the proposed method and the results were discussed from the
viewpoints of the distribution of grain strains and the deformation
restriction by neighboring grains.
3.
Abe, T., R. Kondou, et al. (2003). "Orientation change measured by the
EBSD method and the plastic deformation of grains in polycrystalline
copper." Key Engineering Materials: 535-540.
Change in crystal orientation and strain of individual grains during tensile
plastic deformation are studied to clarify on the microscopic deformation
behavior of polycrystalline copper. The orientation of grain is measured by
electron backscatter diffraction technique in the scanning electron
microscope. The principal strain of grain is also measured by obtaining the
approximated ellipse of strain distribution. The deformation of grains
dependent on their initial orientation and the rotation of the principal
strain during uniaxial tension are clarified.
4.
Abeln, T. G., E. J. Kackenko, et al. (1998). Interface Characterization
Techniques for 304L Stainless Steel Resistance Upset Welds. IMS Conference,
Ottawa, Ontario, Canada.
In an effort to better characterize and classify austenitic stainless steel
resistance upset welds, standard methods have been examined and alternative
methods investigated. Optical microscopy yields subjective classification
due to deformation obscured bond lines and individual perception. The use of
specimen preparations that better reveal grain boundaries aids in
substantiating optical information. Electron microscopy techniques produce
quantitative information in relation to microstructural constituents.
Orientation Imaging Microscopy (OIM) is a relatively new technique for
obtaining objective, quantitative information pertaining to weld integrity,
i.e., percent grain boundary growth across the interface.
5.
Abrutis, A., S. Beauquis, et al. (2003). Reel-to-reel MOCVD for YBCO coated
conductor. High Temp. Superconductivity Group Department of Materials
University of Oxford, Oxford OX1 3PH, United Kingdom, Houston, Texas,
USA.
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 8.5°
on Ni tape and 9° 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 Tc onset at 90 K. Deposition of 2 meter buffered YSZ and
CeO2YBCO films have also been performed showing good in-plane
alignment (φ-scan YSZ: FWHM = 11/ (up to) with a tape velocity set at 4
m/h.
6.
Abstract Milke et al. (Contrib Mineral Petrol 142:15–26, 2001) studied
the diffusion of Si, Mg and O in synthetic polycrystalline enstatite
reaction rims. The reaction rims were grown at 1,000° C and 1 GPa at the
contacts between forsterite grains with normal isotopic compositions and a
quartz matrix extremely enriched in 18O and 29Si. The
enstatite reaction rim grew from the original quartz-forsterite interface in
both directions producing an inner portion, which replaced forsterite and an
outer portion, which replaced quartz. Here we present new support for this
statement, as the two portions of the rim are clearly distinguished based on
crystal orientation mapping using electron backscatter diffraction (EBSD).
Milke et al. (Contrib Mineral Petrol 142:15–26, 2001) used the
formalism of LeClaire (J Appl Phys 14:351–356, 1963) to derive the
coefficient of silicon grain boundary diffusion from stable isotope profiles
across the reaction rims. LeClaire’s formalism is designed for grain
boundary tracer diffusion into an infinite half space with fixed geometry. A
fixed geometry is an undesired limitation in the context of rim growth. We
suggest an alternative model, which accounts for simultaneous layer growth
and superimposed silicon and oxygen self diffusion. The effective silicon
bulk diffusivity obtained from our model is approximately equal within both
portions of the enstatite reaction rim:
DSi,Eneff=1.0–4.3x10-16 m2
s-1. The effective oxygen diffusion is relatively slow in the
inner portion of the reaction rim,
DO,Eneff=0.8–1.4X10-16 m2
s-1, and comparatively fast,
DO,Eneff=5.9–11.6X10-16 m2 s-1, in
its outer portion. Microstructural evidence suggests that transient porosity
and small amounts of fluid were concentrated at the quartz-enstatite
interface during rim growth. This leads us to suspect that the presence of
an aqueous fluid accelerated oxygen diffusion in the outer portion of the
reaction rim. In contrast, silica diffusion does not appear to have been
affected by the spatial variation in the availability of an aqueous
fluid.
7.
Adach, Y., K. Hakata, et al. (2005). "Crystallographic analysis of
grain boundary Bcc-precipitates in a Ni–Cr alloy by FESEM/EBSD and
TEM/Kikuchi line methods." Materials Science and Engineering A
412(1-2): 252-263.
Variant selection of intergranular bcc-Cr precipitates in a Ni–43
mass% Cr alloy was studied by electron backscattering diffraction (EBSD) in
a scanning electron microscope equipped with a field emission gun (FESEM)
and Kikuchi line analysis in transmission electron microscope (TEM). A
single variant was invariably selected at the underlying grain boundaries
(GB) when GB-precipitates were KS-related with respect to both the adjacent
matrix grains. Meanwhile multiple variants were formed at the GB when
GB-precipitates were KS-related to one of the adjacent matrix grains. Theses
variant selections were examined with the tilt angle to underlying GB of
low-energy interphase boundaries and the orientation relationship with
respect to both the adjacent matrix grains. The underlying mechanism was
discussed from the viewpoint of activation energy for nucleation of
two-dimensional nuclei.
8.
Adachi, H., K. Iwabuchi, et al. (2006). "Crystal misorientation
plasticaly formed around fatigue crack-tips in CT specimens from pearlitie
rail steel." Journal of the Society of Materials Science, Japan
55(2): 205-210.
The influence of the stress intensity factor on the microstructure near
fatigue crack tips in rail steels was investigated by the orientation
analysis using high-resolution EBSR. Large changes in crystal orientation
and formation of cell structure were observed around the crack, and a
plastic deformation zone was confirmed to be formed by the stress
concentration at the crack tip. The size of the maximum plastic zone
perpendicular to the crack was quantitatively determined based on the Kernel
average misorientation, which is the average misorientation between all
neighboring pairs of measurement points in the grain, to be 6.9, 8.2 and
>50 µm for Kmax=9.55, 10.88 and 15.84
MPa.m1/2, respectively. For Delta Keff=10.39
MPa.m1/2, a strongly plastic deformation zone of size in 1.3
µm formed around the crack, and maximum plastic deformation zone was
found outside the strongly plastic deformation zone. Although large
misorientation (Dt - 37.5 degrees) was observed between the strongly plastic
deformation zone and the maximum plastic deformation zone, the fluctuation
of the crystal orientation inside the strongly plastic deformation zone was
comparatively small, and the dislocation density was considered to have been
small as well. On the other hand, cell structure was observed in the maximum
plastic zone. A large difference in the development of cell structure was
observed between the grain having a crack and neighbor grain, indicating
that the size of the plastic deformation zone depends strongly on the grain
size.
9.
Adachi, H., K. Osamura, et al. (2005). "Effect of Zr Addition on
Dynamic Recrystallization during Hot Extrusion in Al Alloys." Materials
Transactions 46(2): 211-214.
The presence of Al3Zr precipitates promotes continuous dynamic
recrystallization in Al-Zn-Mg alloys during hot extrusion, resulting in a
fine-grained structure. The mechanism for this phenomenon was investigated
by observing the change in microstructure under hot extrusion using high
resolution EBSP In the rear of the extrusion die mouth, grain boundary
mobility is low since the flow stress is comparatively low and grain
boundary migration is inhibited by Al3Zr particles. Thus, in
order to reduce the deformation-induced high dislocation density, continuous
dynamic recrystallization occurs, which does not involve long-range grain
boundary migration, resulting in a finer-grained structure. The flow stress,
and hence, the mobility of the grain boundary increase near the die mouth.
This promotes long-range grain boundary migration, which reduces the
dislocation density. Continuous dynamic recrystallization is not observed
under these conditions. Since Al3Zr precipitates inhibit
long-range grain boundary migration, increase of the Al3Zr
precipitate content expands the region where continuous dynamic
recrystallization occurs towards the die mouth, resulting in a finer-grained
structure.
10.
Adachi, H., K. Osamura, et al. (2005). "Effect of Zr addition on
microstructure of hot extruded P/M Al-Zn-Mg-Cu alloys." Journal of
Japan Institute of Light Metals 55(4): 164-168.
In this study, the microstructure of hot-extruded and under-extruded Zr
bearing aluminum alloys (Mesoalite10(Registered)-1.3mass%Zr) was
investigated by high-resolution EBSP analysis and the effect of Zr addition
on microstructure formation during hot extrusion was studied. In an extruded
Zr free alloy, coarse fibrous grains elongated to the extrusion direction
were predominantly evolved. And these grains were considered to be formed by
elongation of the original equi-axial grains by extrusion. Whereas, in
extruded Meso1O-1.3 Zr alloy, many fine grains were evolved near the grain
boundaries of the fibrous grains. In under-extruded Meso1O-1.3 Zr alloy,
inhomogeneous local strains were developed near random grain boundaries and
new fine grains were formed by continuous dynamic recrystallization. It is
considered that in aluminum alloys, the addition of Zr promotes continuous
dynamic recrystallization during hot extrusion.
11.
Adachi, Y. and A. Seki (1998). "Diffusion-Induced Recrystallization in
Fe(Zn) System Characterized by Ebsd." Journal of the Japan Institute of
Metals 62(8): 754-760.
12.
Adachi, Y. and K. Tsuzaki (2005). Coherent-to-incoherent transition of
intergranular bcc-precipitates by pre-/post-deformations in a ni-43Cr alloy.
International Conference on Solid-Solid Phase Transformations in Inorganic
Materials 2005, Phoenix, Arizona, USA.
To understand the physical meaning of 'dynamic'
transformation/precipitation, effects of light deformations before and after
precipitation (pre-deformation and post-deformation) on orientation
distribution of intergranular bcc-precipitates were examined in a
Ni-43mass%Cr alloy by electron backscattered diffraction. The deviation
angles from both the plane/direction parallel orientation relationships in
the Kurdjumov-Sachs orientation relationship of intergranular precipitates
were evaluated with both pre- and post-deformations. Based on this result,
microstructural evolution of intergranular precipitates formed dynamically
was discussed with particular attention to coherent-to-incoherent transition
of precipitates.
13.
Adachi, Y. and K. Tsuzaki (2005). "Coherent-to-incoherent transition of
intergranular bcc precipitates by pre-/post-deformations in a Ni-43Cr
alloy." ISIJ International 45(11): 1703-1710.
Effects of light deformations before and after precipitation
(pre-deformation and post-deformation) on orientation distribution of
intergranular bcc-precipitates were examined in a Ni-43mass%Cr alloy by
electron backscattered diffraction. It was found that the deviation angles
from both the plane/direction parallel orientation relationships in the
Kurdjumov-Sachs orientation relationship of intergranular precipitates were
increased by both pre- and post-deformations, but post-deformation was more
effective. Based on this result, microstructural evolution of intergranular
precipitates formed dynamically was discussed with particular attention to
coherent-to-incoherent transition of precipitates.
14.
Adachi, Y. and K. Tsuzaki (2005). "Light Pre-Deformation Induced
Misorientation of Grain Boundary Bcc-Precipitates from the Kurdjumov-Sacks
Relationship in a Ni-Cr Alloy." Metals and Materials International
11(5): 341-349.
Crystallography of grain boundary (GB) bcc-precipitates formed in a lightly
pre-deformed fcc-matrix phase was examined in a Ni-43Cr alloy by EBSD with
emphasis on a misorientation from the Kurdjumov-Sachs orientation
relationship. The misorientation of GB bcc-precipitates became somewhat
larger when the matrix phase was lightly pre-deformed. The GB
bcc-precipitates were preferentially formed at the intersection of
geometrically necessary dislocation boundaries (GNB) with grain boundaries.
In contrast, the pre-deformation did not influence the misorientation of
intragranular bcc-precipitates. The preferential precipitation and the
increased misorientation at the GNB-GB intersection- were discussed.
15.
Adams, B. L. (1993). "Orientation Imaging Microscopy." Institute
of Physics Conference Series (138): 489-494.
16.
Adams, B. L. (1993). "Orientation imaging microscopy: application to
the measurement of grain boundary structure." Materials Science and
Engineering A 1993: 59-66.
The method or orientation imaging microscopy (OIM), which utilizes rapid,
direct measurements of local lattice orientation on a grid of points fixed
upon flat surfaces sectioned from polycrystals, is described, and connected
with established stereological theory. Examples of OIM applied to an
Fe-2wt.%Si alloy are presented. Procedures associated with the SV/PL
stereology are extended to obtain a new SV/f2 stereology linking two-point
statistics of lattice orientation with the distribution of grain boundary
structure. The chief advantage of the new stereology is that it can be
implemented directly from OIM. It is shown that the reliability of the
method depends, not only on the number of sectioned surfaces interrogated
(as is the case with established SV/PL stereology), but also on the
magnitude of the spacing between grid points. (Author abstract) [References:
18]
17.
Adams, B. L. (1994). Orientation imaging of microstructures. Fifty-Second
Annual Meeting Microscopy Society of America/Twenty-Ninth Annual Meeting
Microbeam Analysis Society, New Orleans, LA, San Fancisco Press,
Inc.
18.
Adams, B. L. (1997). "Advances in the Mesoscale Approach to
Structure-Sensitive Properties Relations in Polycrystalline
Materials."
19.
Adams, B. L. (1997). "Orientation imaging microscopy: Emerging and
future applications." Ultramicroscopy 67(1-4): 11-17.
Orientation imaging microscopy (OIM), which images the microstructure using
the electron backscattered diffraction probe, has proven to be a powerful
tool for the study of polycrystalline materials. OIM's chief strength lies
in its ability to couple the morphological aspects of microstructure, with
lattice orientation. With spatial and angular resolution of at least 100 nm
and 1°, OIM is ideally suited to investigations at the mesoscale. In
this paper three examples are described which illustrate emerging and future
applications of OIM to important problems in materials science at the
mesoscale. The first example is the use of higher-order point statistics to
obtain improved bounds on structure-insensitive properties. It is emphasized
that the approach may be used, not only to enhance material properties, but
also to control their variability. The second example is an emerging
analysis to map the relationships between the character (type) of grain
boundaries and their intrinsic properties. The main idea is illustrated for
mappings linking character and excess free energy. The third example focuses
on the ability of OIM to measure lattice curvature, and to thereby obtain
information about the geometrically necessary dislocation content of the
microstructure. This example is illustrated by analysis to extract the
dislocation density tensor. (Author abstract) [References: 21]
20.
Adams, B. L. and C. T. Wu (1996). Mapping the Grain Boundary Character/Free
Energy Relationship in Polycrystalline Materials: Pure <100> and
<111> Tilt Boundaries. Eleventh International Conference on Textures
of Materials, Xi'an, China, International Academic Publishers.
21.
Adams, B. L. and T. Olson (1998). "The Mesostructure - Properties
Linkage in Polycrystals." Progress in Materials Science 43(1):
1-87.
22.
Adams, B. L., B. Cai, et al. (2005). Microstructure characteristics of
friction stir processed A1 7075 via macroscopic approach. 2006 TMS Annual
Meeting, San Francisco, California, USA.
A new methodology, called macroscopic or 3-dimensional approach, coupling
observations of microstructural characteristics with their corresponding
geometrical locations, is introduced to describe the microstructure
characteristics of friction stir processed 7075-T6 A1. Data is recovered
from plan view in the microstructure, with spatial specificity in the
transverse plane. Orientation imaging microscopy (OIM) was extensively
employed; and the results via OIM are presented and discussed. Grain sizes
at the welding center decrease from top to bottom. Very fine grains were
found in the weld nugget with prominent alignment. This observation
indicates that grains in the nugget are not 3-dimensional equiaxial, but
2-dimensional. Different regions of welds can be readily detected from
contour plots of grain sizes in transverse cross section.
23.
Adams, B. L., B. L. Henrie, et al. (2000). Structure-Property Relations:
EBSD-Based Material-Sensitive Design. Electron Backscatter Diffraction in
Materials Science. A. J. Schwartz, M. Kumar and B. L. Adams. New York,
Kluwer Academic/Plenum Publishers: 171-9.
24.
Adams, B. L., B. S. El-Dasher, et al. (2003). Grain rotations during tensile
deformation of columnar tantalum. Multiscale Phenomena in Materials -
Experiments and Modeling Related to Mechanical Behavior, San Francisco, CA,
United States.
We report on tensile tests performed on thin sheet samples of tantalum that
have a near-columnar structure. By annealing sheet of approximately 1 mm
thickness at high temperatures, a columnar structure is generated with grain
boundaries nearly perpendicular to the flat surfaces. The purpose of the
experiments is to investigate the mechanical behavior in terms of crystal
plasticity in a geometry that is readily amenable to both experimental
characterization and computer simulation. Automated electron backscatter
diffraction (EBSD) has been used to obtain orientation maps both before and
after deformation. For the small strains used in this study (<10%), the
grains deform rather uniformly with little evidence of cell formation.
Analysis of the lattice rotations shows considerable scatter in the rotation
axis and demonstrates significant disagreement with polycrystal plasticity
calculations.
25.
Adams, B. L., C. L. Bauer, et al. (1999). Extraction of grain boundary
energies from triple junction geometry. Twelfth International Conference on
Textures of Materials (ICOTOM 12), McGill University, Montreal, Canada, NRC
Research Press.
26.
Adams, B. L., D. J. Dingley, et al. (1994). "Orientation Imaging
Microscopy: New Possibilities for Microstructural Investigations using
Automated BKD Analysis." Materials Science Forum 157-62:
31-42.
A new microscopy, called Orientation Imaging Microscopy, is described.
Imaging results from precise measurements of local lattice orientation
rapidly obtained by Backscattered Kikuchi Diffraction. The hardware
configuration of the microscope is described, and a description of image
formation is presented. Applications of the method to several materials of
differing lattice structure are described. Connections of the microscopy
with various aspects of meodern texture analysis are emphasized.
27.
Adams, B. L., D. J. Dingley, et al. (1995). Method and Apparatus for
Identification of Crystallographid Defects. USA: 12.
An imaging apparatus includes a scanning electron microscope which is
controlled to bombard numerous points of a material sample with an electron
beam. Backscatter diffraction patterns are collected by an image collection
system which may include a slower responding video camera and a faster
responding diode array. For a baseline point, and electron backscatter
patteren collected at the video camera is analyzed to identify
representatiive pixels which reside along Kikuchi bands. Backscatter images
from subsequent points are rapidly compared with the baseline to detect
changes. When changes are not detected, EBSPs are not analyzed. When changes
are detected, EBSPs are analyzed to generate new baselines. The resulting
collection of analyzed EBSPs are processed to identify microstructure
attributes and to characterize defects.
28.
Adams, B. L., G. H. Campbell, et al. (1999). Orientation imaging microscopy
investigation of the compression deformation of a 011 ta single
crystal.
High-purity tantalum single crystal cylinders oriented with 110 parallel to
the cylinder axis were deformed 10, 20, and 30 percent in compression. The
samples were subsequently sectioned for characterization using Orientation
Imaging Microscopy (O&;I) along two orthogonal sectioning planes: one in
the plane containing 001 and 110 (longitudinal) and the other in the plane
containing 1{anti 1}0 and 110 (transverse). To examine local lattice
rotations, the Euler angles relative to a reference angle at the section
center were decomposed to their in-plane and out-of-plane components. The
in-plane and out-of-plane misorientation maps for all compression tests
reveal inhomogeneous deformation everywhere and particularly large lattice
rotations in the comers of the longitudinal section. Of particular interest
are the observed alternating orientation changes. This suggests the
existence of networks of dislocations with net alternating sign that are
required to accommodate the observed rotations. Rotation maps from the
transverse section are distinctly different in appearance from those in the
longitudinal plane. However, the rotation maps confirm that the rotations
observed above were about the 1{anti 1}0 axis. Alternating orientation
changes are also observed on this section. Results will be directly compared
with crystal rotations predicted using finite element methods and reviewed
in light of the LLNL Multiscale Materials Modeling Program.
29.
Adams, B. L., P. S. Lee, et al. (1999). Spatial correlations of orientation,
orientation clustering and the variance of the orientation distribution
function. ICOTOM-12.
30.
Adams, B. L., S. I. Wright, et al. (1993). "Orientation Imaging: The
Emergence of a New Microscopy." Metallurgical Transactions A
24(4): 819-831.
31.
Adams, B. L., S. Ta'asan, et al. (1999). "Extracting Grain Boundary and
Surface Energy from Measurement of Triple Junction Geometry." Interface
Science.
Measurement of the geometry of triple junctions between grain boundaries in
polycrystalline materials generates large sets of dihedral angles from which
maps of the grain boundary energy may be extracted. A preliminary analysis
has been performed for a sample of magnesia based on a three-parameter
description of grain boundaries. An extended form of orientation imaging
microscopy (OIM) was used to measure both triple junction geometry via image
analysis in the SEM and local grain orientation via electron back scatter
diffraction. Serial sectioning with registry of both in-plane images and
successive sections characterizes triple junction tangents from which true
dihedral angles are calculated. We apply Herring’s relation at each
triple junction, based on the assumption of local equilibrium at the
junction. By limiting grain boundary character to a (three parameter)
specification of misorientation for the preliminary analysis, we can neglect
the torque terms and apply the sine law to the three boundaries. This
provides two independent relations per triple junction between grain
boundary energies and dihedral angles. Discretizing the misorientation and
employing multiscale statistical analysis on large data sets allows
(relative) grain boundary energy as a function of boundary character to be
extracted from triple junction geometry. A similar analysis of thermal
grooves allows the anisotropy of the surface energy to be measured in
MgO.
32.
Adams, B. L., W. Z. Jun, et al. (1990). "Analysis of Interface Damage
Heterogeneity in Polycrystalline Materials." Acta Metallurgica et
Materialia 38(6): 953-966.
The Interface Damage Function (IDF) defining fractional damage of
intercrystalline interfaces in polycrystalline materials, with functional
dependence upon lattice misorientation and boundary normal orientation, is
described. A method of section analysis to calculate the IDF is derived; it
is shown to depend upon a convolution with the Intercrystalline Structure
Distribution Function (ISDF) which has been defined in previous work. This
convolution is expressed in a double integral equation which is solved by
the Fourier method. Application of the theory to cavitation damaged OFHC
copper is described. Illustrated is a rich structure of the IDF which
illuminates the mechanisms of heterogeneity in creep damage. Random
high-angle boundaries are found to be remarkably damage resistant, while
some special boundaries are preferentially damaged. A varied response of the
damage to shear and normal components of the applied stress is also
observed.
33.
Adams-Hughes, M., N. Chandra, et al. (2005). Microstructure characteristics
of friction stir processed A1 7075 via macroscopic approach. 2006 TMS Annual
Meeting, San Francisco, California, USA.
Friction Stir Processing (FSP) was employed to study its effect on the
microstructure and texture of AA 5052 alloy. The material was characterized
using Orientation Imaging Microscopy (OIM) and X-ray texture. A correlation
was made between the processing parameters (rotation and translation
speeds), microstructure and the microtexture developed in the material. The
processing resulted in significant grain refinement, when compared to the
starting material. Although the rotation and translation speeds played roles
on the development of the microstructure, the rotation speed had a greater
impact. Reduction in the rotation speed resulted in further refinement of
the grain size. A detailed characterization of the samples produced by FSP
has been carried out, and the mechanism for recrystallization is discussed
in this paper.
34.
Addessio, L. B., E. K. Cerreta, et al. (2005). "Mechanical Behavior of
Zirconium and Hafnium in Tension and Compression." Metallurgical and
Materials Transactions A 36A(11): 2893-2903.
The mechanical behavior and substuctural evolution of highly textured
hafnium (Hf) has been examined in tension and compression and compared to
the mechanical response of Zirconium (Zr). The quasi-static work-hardening
rate as a function of strain for both metals exhibits a compression-tension
asymmetry. Both Zr and Hf exhibit a downward work-hardening response in
tension, while each displays a parabolic and then concave upward
work-hardening behavior in compression. Additionally, Hf dispays higher flow
stresses than Zr both in tension and compression. The stress-strain and
strain-hardening curves for Zr and Hf have been characterized in terms of
their propensity for deformation twinning and evolution of substructure with
strain. Differences in the work-hardening rates and flow stresses as a
function of the sense of the applied load and material are discussed in
terms of slip-twin interactions during deformation.
35.
Aernoudt, E., A. Walentek, et al. (2005). "Towards a description of
complex pearlite structures." Zeitschrift fur Metallkunde 96(9):
1032-1037.
Pearlite structures in eutectoid carbon steel seldom are perfectly lamellar.
Structures in thermomechanically processed material in particular often
consist of complex mixtures of lamellar, degenerated, and globular domains.
In order to open the possibility of modelling structure-property
relationships for such material, techniques have to be developed to
quantitatively describe the morphology of its pearlite structure. The
present article shows how EBSD and the Hough transform can give
complementary information that can be further developed into a quantitative
description of pearlitic structures.
36.
Afer, H., N. Rouag, et al. (2005). Comparison between the growth behaviour
of the small Goss grains and that of the large matrix grains in silicon
steels. Influence of the textured cluster presence. Textures of Materials -
ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
In the Fe-3%Si alloys, grade Hi-B with AlN and MnS as inhibitors, the Goss
grains that abnormally grow have not a size greater than the average size of
the primary matrix. In such a heterogeneous microstructure, the size factor
is not a required condition for the secondary recrystallization. The
abnormal growth onset of the small Goss grains appears to be related to a
particular behaviour of their grain boundaries and therefore to the local
texture so as the distribution of the inhibitors. The presence and the
evolution of textured clusters ensure to the small Goss grains a favourable
neighbourhood to grow. In this study, their growth ability is compared with
that of the largest grains of the matrix. The modified Monte-Carlo approach,
performed in the present study, considers the local environment of each
grain, so that the growth rate is dependent of its real spatial position,
the matrix heterogeneity is then taken into account.
37.
Afera, H., N. Rouaga, et al. (2004). "Onset of abnormal growth related
to the crystallographic neighbourhood from the texture function. Application
to Goss grain growth in magneticsheets of Fe–3%Si." Journal of
Crystal Growth 268: 320-327.
In the magneticsheets Fe–3%Si of HiB type, with AlN and MnS
inhibitors, the Goss texture is obtained by a sudden and fast growth of the
small size grains, with Goss orientation {1 1 0}<0 01>. This behaviour
is not in good agreement with the classical laws of grain growth. In the
present study, the abnormal grain growth is related to the material texture
and to the texture component evolution, by carrying out Monte Carlo
simulation. The onset of abnormal growth of Goss grains seems to be linked
to the existence of a favourable crystallographic neighbourhood. The grains
that grow abnormally do not have a size greater than the average size in the
matrix; their ability to grow in an abnormal way can be related to the
behaviour of grain boundaries, which surround them. The growth of a given
grain is controlled by the local evolution of grain boundaries around that
considered grain and not by the average evolution of the totality of the
matrix; the whole effect of the matrix can hide the effect of matrix
heterogeneity. The experimental characterisation of matrix parameters is
performed by Electron Back Scattering Diffraction (EBSD).
38.
Ago, H., K. Nakamur, et al. (2005). "Aligned growth of isolated
single-walled carbon nanotubes programmed by atomic arrangement of substrate
surface." Chemical Physics Letters(408): 433-438.
Highly aligned and isolated single-walled carbon nanotubes (SWNTs) were
grown on the R-face (1 1 0 2) and A-face (1 1 2 0) surfaces of sapphire
(Al2O3) substrates by catalytic chemical vapor
deposition. On the basis of the electron backscatter diffraction (EBSD)
analysis, we have found that the SWNTs are aligned along the specific
crystalline directions corresponding to the anisotropic
pseudo-one-dimensional array of Al atoms on these surfaces. This suggests
that the Al array guides the SWNT growth due to the strong interaction
between the Al atoms and nanotubes. On the other hand, a random orientation
has been observed for the SWNTs grown on the C-face (0 0 0 1) substrate,
reflecting the isotropic arrangement of Al atoms. These findings indicate
that the strong interaction between the SWNTs and substrate surface is
applicable for patterning or integrating SWNTs in nanoelectronics
applications.
39.
Ahmad, E., A. A. Khan, et al. (2003). Ultra grain refinement in a low alloy
steel. 8. International Symposium on Advanced materials, Islamabad, Doctor
A.Q. Khan Research Labs., Islamabad, Pakistan, Islamabad (Pakistan).
The phenomenon of Grain Refinement was studied in a steel containing 0.15%C,
0.32%Si, 1.4%Mn and 0.43%V Steel. Transformational Grain Refinement (TGR)
was applied to give a reasonable refinement in the grain size. Initial
austenite grain size was found to be 50 micro m, determined by quenching the
specimen in iced brine solution from 1150 deg. C. A rolling reduction of
about 67% at 900 deg. C followed by air cooling gave a final thickness of
specimen of 3mm. Cold rolling and recrystallisation of these specimens gave
further refinement in grain size and about 1 micro m was obtained. Electron
Backscattered Diffraction (EBSD) technique was used to determine the low
angle grain boundaries (LAGB) and high angle grain boundaries (HAGB),
effectively used to determine the substructure contribution at various
stages of recrystallisation.
40.
Ahmed, H., M. A. Wells, et al. (2005). "Modelling of microstructure
evolution during hot rolling of AA5083 using an internal state variable
approach integrated into an FE model." Materials Science and
Engineering A 390(1-2): 278-290.
Hot rolling, a critical process in the manufacturing of aluminum sheet
products, can significantly impact the final properties of the cold rolled
sheet. In this research, a mathematical model was developed to predict the
through-thickness thermal and deformation history of a sheet undergoing
single stand hot rolling using the commercial finite element (FE) package,
ABAQUS™. A physically based internal state variable microstructure
model has been incorporated into the FE simulation for an AA5083 aluminum
alloy to predict the evolution of the material stored energy and the
subsequent recrystallization after deformation is complete. The
microstructure predictions were validated against experimental measurements
conducted using the Corus pilot scale rolling facility in IJmuiden, the
Netherlands for an AA5083 aluminum alloy. The model was able to predict the
fraction recrystallized as well as the recrystallized grain size reasonably
well under a range of industrially relevant hot deformation conditions. A
sensitivity analysis was carried out to determine the influence of changing
the material constants in the microstructure model and deformation
conditions on the predicted recrystallization behaviour. The analysis showed
that the entry temperature was the most sensitive process parameter causing
significant changes in the predicted driving force for recrystallization,
nucleation density, fraction recrystallized, and recrystallized grain
size.
41.
Ahmed, J., A. J. Wilkinson, et al. (1999). "Study of dislocation
structures near fatigue cracks using electron channelling contrast imaging
technique (ECCI)." Journal of Microscopy - Oxford 195(Pt. 3):
197-203.
The fatigue of copper single crystals, orientated for single slip, has been
studied using electron channelling contrast imaging in a scanning electron
microscope. With the incident beam set at the Bragg condition, changes in
the backscattered electron intensity occur as the beam is scanned over
dislocations that cause a local tilting of the diffraction planes. This
technique allows the evolution of dislocation structures over large areas to
be followed through different stages of the fatigue life. Furthermore, it
enables direct imaging of dislocation configurations at crack tips. The
technique is compared with transmission electron microscopy and electron
backscatter diffraction in its application to fatigue studies.
42.
Ahmed, M. M. I. and T. G. Langdon (1983). "The Effect of Grain-Size on
Ductility in the Superplastic Pb-Sn Eutectic." Journal of Materials
Science 2(7): 337-340.
43.
Ahn, J.-P., J.-C. Lee, et al. (2003). "Work-softening behavior of the
ultrafine-grained Al alloy processed by high-strain-rate, dissimilar-channel
angular pressing." Metallurgical and Materials Transactions A
34A(3): 625-632.
Commercially pure Al alloy sheets were processed using high-strain-rate,
dissimilar-channel angular pressing (DCAP) for as many as 100 passages
through a channel with φ = 120 deg, to investigate the work hardening
caused by a low strain level (ε < 2) and the work softening
caused by an extremely high strain level (3 < ε < 58). The
hardness of the alloy increased significantly by a factor of 2 at strains
less than similar to 2, while a gradual decrease in the hardness was
observed at strains greater then similar to 2. The work-hardening and the
work-softening behaviors observed from the Al alloy were analyzed by
correlating the measured properties with microstructural evolutions observed
by transmission electron microscopy (TEM). A detailed
microstructural-evolution sequence occurring at successive strain stages was
also investigated based on TEM and electron backscattered diffraction
(EBSD).
44.
Ahn, S. and J. B. Cohen (1988). "The Distribution of Sigma-Boundaries
in Sintered Magnetite." Materials Science and Engineering
100(APR): 255-260.
45.
Ahn, S. J., S. Ahn, et al. (2003). "Study on the non-linear property of
abnormally grown grain ZnO." Materials Chemistry and Physics
82(2): 410-413.
Abnormally grown large size ZnO grains were prepared by applying a specific
uniaxial pressure on the additive-free ZnO compact specimen. The average
grain size was larger than 500μm after heat treatment at 1490 the compo C
for 4h in air atmosphere. The crystallographic examination was performed
using X-ray diffraction (XRD) and electron back scatter diffraction (EBSD)
and the current-voltage characteristics were measured with the aid of
microscopic probes. These additive-free ZnO grains showed non-linear
current-voltage characteristics especially at a high current region. From
the several experimental results, we found the origin of the non-linearity
can be attributed to the presence of stress within grains which is
introduced during the growth procedure. Copyright 2003 Elsevier B.V. All
rights reserved. 11 Refs.
46.
Akahori, T., Y. Fujiwara, et al. (2006). "Formation of well alligned
rod type eutectic structure for bulk β-FeSi2 by solid
reaction and its orientation analysis." Journal of the Society of
Materials Science, Japan 55(2): 148-152.
A few problems are still remained in a single bulk b-FeSi2
formation from liquid phase. As the first step of a single bulk
β-FeSi2 formation from a solid reaction between highly
oriented two phases, unidirectional solidification method was applied to the
FeSi2 composition alloy. The growth rates were changed from
1.7µm/s to 5.4µm/s. The typical rod type eutectic was formed and
the matrix was α phase and the rod was ε phase. The size of
the phase increased with decrease of the growth rate. The matrix phase was a
single crystal below 3.4µ m/s and its orientation was <100>. All
of phase were alligned to <100> independent of growth rate.
47.
Akiniwa, Y., H. Kimura, et al. (2005). "Misorientation analysis of
plastic deformation of austenitic stainless steel by EBSD and X-ray
diffraction methods." Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions
of the Japan Society of Mechanical Engineers, Part A 71(12):
1722-1728.
The misorientation introduced into an austenitic stainless steel (SUS 316)
by plastic deformation was masured with the electron back scattering
diffraction (EBSD) and the X -ray diffraction (XRD) techniques. Three
parameters related to miorientation distribution, i.e. grain orientation
spread (GOS), grain average misorientation (GAM) and kernel average
misorientation (KAM), were calculated from the orientation measurements by
EBSD The misorienation between neighboring measured points. KAM, was larger
close to the grain boundary where the slip propagation was difficult. The
average of misorientation between neighboring points within one grain is
GAM. The GAM value averaged over the measured reagion increased
proportionally with the plastic strain to about 20%, and leveled off at
higher strains. The average of the misorientation spread within one grain,
GOS, also showed similar increase like GAM. The total misorientation of a
grain measured by XRD also showed a proportional increase with the plastic
strain to about 10%, and it was difficult to measure the total
misorientation above that strain because Debye ring became continuous ring.
Both EBSD and XRD can be used as a tool to measure the plastic strain in the
local area, and the limit of strain to be measured was 30% for the former
and 10% for the latter.
48.
Akiyama, M., Y. Neishi, et al. (2003). "Trigger for the occurrence of
grain coarsening phenomenon of BS304S31 austenite stainless steel under
small plastic strain at high temperature." Engineering Computations
20(5/6): 499-512.
Observation by optical microscopy and EBSP have made it clear that the
trigger for the grain coarsening phenomenon of austenite stainless steel
BS304S31 may be the stacking faults concentrating selectively in a thin
layer lying just beneath the grain boundary. When macroscopic plastic strain
reached 6 percent, selective concentration of stacking faults was observed.
When it reached 20 percent, the distribution of stacking faults became
uniform in each grain. After these specimens were heated, concentration of
stacking faults disappeared, and grain coarsening occurred at the point with
6 percent strain, but no grain coarsening occurred at the point with 20
percent strain. In order to investigate this concentration of stacking
faults, an attempt was made to analyze the deformation in each crystal by
using image-based FEM. The result suggested that there is a possibility that
plastic strain concentrates in the vicinity of the grain boundary when the
macroscopic plastic strain is small.
49.
Alam, M. N., M. Blackman, et al. (1954). "High-angle Kikuchi
Patterns." Proceedings of The Royal Society of London A221:
224-242.
50.
Alani, R., D. P. Field, et al. "SEM Specimen Preparation by Broad Ion
Beam Etching for Enhanced Channeling and Orientation Imaging."
It is well known that the "channeling contrast" and EBSD pattern
formation, which is the basis for "orientation imaging microscopy"
(OIM), is highly sensitive to specimen surface quality in SEM studies.
Typically, specimens for these studies are prepared by a combination of
mechanical grinding, then chemical etching or electropolishing. As an
alternative to the chemical step(s) in this technique, we report a method
based on broad ion beam etching equipment. This alternative method is more
universal and reliable for enhanced channeling contrast and EBSD/OIM of
metallic materials.
51.
Al-Badairy, H., A. J. Papworth, et al. (2003). FEG-SEM and STEM
Investigation of High Temperature FeCrAl(RE) Alloys. Corrosion Science in
the 21st Century, Manchester, UK.
Field emission gun scanning electron microscopy (FEGSEM) with electron
backscattered diffraction (EBSD) and field emission gun scanning
transmission electron microscopy (FEGSTEM) have been used to study the
recrystallisation microstructure and the oxidation behaviour of ultra-high
purity Fe-20Cr-5Al model alloys and commercial Fe-20Cr-5Al alloys. The model
alloys contain controlled additions of impurities such as phosphorus and
carbon and added levels of more beneficial elements such as zirconium and
titanium. Samples were studied in the asreceived state and after oxidation
at temperatures ranging from 900 deg C to 1300 deg C and for times up to 5h
in air. Initial analysis showed that recrystallisation commenced after 1h of
oxidation at 900 deg C. Complete recrystallisation was achieved after 1h of
oxidation at 1000 deg C. FEGSEM-EBSD analysis did not reveal any
crystallographic preferred orientation in the studied alloys. However,
during in-situ annealing (at 600 deg C for 4h) of YHfAl, FEGSEM-EBSD showed
the development of a strong texture with < 111 > normal to the plane
of the sheet. Oxidation at a higher temperature (1300 deg C) revealed that
the alpha-alumina formed on the model alloy with a high level of phosphorus
was much thicker than those observed on the rest of the investigated alloys.
As a result this will shorten the lifetime of the alloy, leading to
catastrophic failure. (This is an unrefereed preprint.)
52.
Albert, S. K., M. Kondo, et al. (2005). "Improving the Creep Properties
of 9Cr-3W-3Co-NbV Steels and their Weld Joints by the Addition of
Boron." Metallurgical and Materials Transactions A 36A(2):
333-343.
New ferritic steels with a controlled addition of boron have been developed
recently for ultrasupercritical fossil power plants. These steels possess
excellent creep resistance compared to conventional steels like P91, P92,
P122, etc., and this has been attributed to the delay in coarsening of the
carbides during creep owing to partial replacement of carbon by boron in
these carbides. However, the susceptibility of the weld joints of the
boron-containing ferritic steels to type IV cracking, which significantly
brings down the rupture life of the weld joints, has not been investigated
so far. In the present work, the creep properties of recently developed
9Cr-3W-3Co-NbV steels with boron contents varying from 47 to 180 ppm and of
their weld joints have been studied. Creep tests were carried out at 923 K
in the stress range of 140 to 80 MPa. Specimens were examined for particle
coarsening using field-emission scanning electron microscopy, and the boron
content in the precipitates was estimated using field-emission auger
electron spectroscopy (FE-AES). The grain size of the parent metal and the
heat-affected zone (HAZ) were estimated using electron backscattered pattern
(EBSP) imaging. Results showed that the creep properties of the steels with
90 and 130 ppm boron and of their weld joints are superior to those of the
P92 steels and its weld joints. Further, no weld joints exhibited type IV
cracking. No significant coarsening of the carbides was observed, not only
in the parent metal but also in the HAZ of the steels with 90 ppm of boron.
In addition to the delay in carbide coarsening, the large prior-austenite
grain size of the parent metal and the absence of a conventional
fine-grained HAZ (FGHAZ) in the weld joints also seem to have a beneficial
effect on improving the creep properties of these steels and their weld
joints.
53.
Alexandreanu, B. and G. S. Was (2006). "The role of stress in the
efficacy of coincident site lattice boundaries in improving creep and stress
corrosion cracking." Scripta Materialia 54(6):
1047-1052.
While a consensus appears to exist on the improved resistance to
intergranular stress corrosion cracking (SCC) initiation of coincidence site
lattice boundaries (CSLBs) in austenitic alloys, the effect of such
boundaries on SCC propagation is not well understood. Experimental results
show a direct correlation between IGSCC and creep rate via the fraction of
CSLBs, as well as a cause-and-effect relationship between grain boundary
deformation and cracking. The objective of this paper is to highlight the
importance of deformation in the SCC behavior.
54.
Alexandreanu, B., B. Capell, et al. (2001). "Combined effect of special
grain boundaries and grain boundary carbides on IGSCC of
Ni–16Cr–9Fe–xC alloys." Materials Science and
Engineering A 300: 94-104.
Susceptibility to intergranular stress corrosion cracking in
Ni–16Cr–9Fe–xC alloys in 360°C primary water is
reduced with increasing fraction of special grain boundaries, i.e.
coincident site lattice boundaries (CSLB) and low angle boundaries, and
grain boundary carbides. Intergranular stress corrosion cracking (IGSCC) was
investigated using interrupted constant extension rate tensile tests in a
primary water environment at 360°C. Thermal–mechanical treatments
were used to increase the fraction of special boundaries from approximately
20–25% to between 30 and 40%. In a carbon-doped heat, further heat
treating was used to precipitate grain boundary carbides preferentially on
high-angle boundaries (HAB). Orientation imaging microscopy was used to
determine the relative grain misorientations and scanning electron
microscopy (SEM) was used to identify specific grain boundaries after each
interruption. After each strain increment, the same regions in each sample
were examined for cracking. Results showed that irrespective of the
microstructure condition, CSLBs always cracked less than HABs. Results also
showed that IGSCC is reduced with increasing solution carbon content, and
for the same amount of carbon in solution, the addition of grain boundary
carbides reduced IGSCC still further. The best microstructure was the one
consisting of an enhanced CSLB fraction and chromium carbides precipitated
preferentially on high-angle boundaries.
55.
Alhaidary, J. T., E. R. De los Rios, et al. (1983). "The
Plastic-Deformation of Polycrystals.1. Aluminum Between Room-Temperature and
400-Degrees-C." Philosophical Magazine A 47(6): 869-890.
56.
Allehaux, D., C. Desrayaud, et al. (2005). "Correlation between
microstructure and microhardness in a friction stir welded 2024 aluminium
alloy." Scripta Materialia 52(8): 693-697.
A 2024-T351 aluminium alloy has been friction stir welded and the
microstructures investigated. An inner HAZ hardness minimum was a result of
an overaged S phase, whereas an outer minimum was believed to be due to
precipitate dissolution. An interjacent HAZ maximum was attributable to the
presence of very fine S phase precipitates. The nugget zone contained
similar to 4 μm grains and complex dislocation structures. Published by
Elsevier Ltd. All rights reserved.
57.
Allen, V. M., M. Preuss, et al. (2005). Evolution of Texture in Zirconium
Alloy Tubing During Processing. Textures of Materials - ICOTOM 14, Leuven,
Belgium, Trans Tech Publications.
Electron backscattered diffraction (EBSD) has been used to determine
microtexture in a zirconium alloy tube subject to interrupted pilgering and
therefore exhibiting varying amounts of deformation as a function of axial
position along the transition between the initial and final size. Texture
and hardness measurements have been made as a function of the distance
through the tube wall thickness and along the tube length. Texture results
have been compared with co-located hardness measurements. The results show a
systematic variation in the deformation texture with changes in Q (the ratio
of the reduction in thickness to reduction in diameter). This is consistent
with previous observations of the effect of Q on texture evolution in
zirconium alloys. It is demonstrated that the texture measurements can be
correlated well with the anisotropy in strength determined from hardness
measurements.
58.
Al-Samman, T. and G. Gottstein (2004). Influence of starting textures on the
development of texture and microstructure during large strain hot rolling of
pure magnesium. 2nd International Conference on Texture and Anisotropy of
Polycrystals (ITAP 2), Metz, France, Balaban Publishers; Scitec
Publications.
The plastic behaviour of hexagonal metals such as magnesium is very
anisotropic and substantially affected by crystallographic texture. In this
work, samples of pure magnesium with different starting textures were hot
rolled at 400 degrees C in one rolling pass to different final thicknesses
of 5%, 10%, 30%, 50%, 70%, 90%. The microstructure and macrotexture
evolution were examined by optical microscopy (OM) and X-ray diffraction,
respectively. Further, microtexture analysis was done by EBSD Texture
modelling with LAPP using an FC Taylor model, based on the expected active
slip and twinning modes was performed. The results were compared with the
measured textures.
59.
Altuna, M. A. and I. Gutierrez (2005). "Microstructure mechanical
properties relationship in bainitic structures." Revista de Metalurgia
(Madrid) 41(5): 357-364.
In the present work, the microestructures and their mechanical properties
have been studied in different bainitic structures. Therefore, different
bainitic morphologies have been produced by isothermal treatments carried
out at different temperatures. For these steels, 400-450lled in a C is the
optimum range of temperatures in order to obtain bainitic structures. If the
Temperature is higher, perlite is also formed and if it is lower, martensite
is obtained during quenching. SEM and EBSD/OIM techniques were applied in
order to study the microstructure. Tensile tests were carried out for
mechanical characterization.
60.
Alvi, M. H., A. P. Brahme, et al. (2003). Recrystallization kinetics in hot
rolled aluminum: A combined experimental and simulation approach. Automotive
Alloys 2003, Increasing Energy Efficiency In Aluminium, And Universities
Servicing Education, Research And Technology Internationally For The
Aluminium And Light Metals Industries Symposia, San Diego, California,
USA.
Recrystallization kinetics and texture evolution in aluminum alloy are
analyzed by microhardness variation and EBSD in a SEM. The parameters for
recrystallization kinetics were obtained by assuming a
Kolmogorov-Johnson-Mehl-Avrami type behavior. Variation in the evolution of
different texture components is analyzed by EBSD and X-ray diffraction. The
experimental results are compared with simulated calculations using Monte
Carlo method. A 3-dimensional model for the recrystallization process has
been developed that uses the experimental microstructures. The details of
various aspects of modeling are discussed along with the possible
improvements to obtain desirable correspondence with the observed
structures.
61.
Alvi, M. H., B. S. El-Dasher, et al. (2003). Analysis of recrystallization
kinetics from microstructural evolution and micro-hardness determination.
Third Symposium on Hot Deformation of Aluminum Alloys III as held at the
2003 TMS Annual Meeting, 184 Thorn Hill Road, Warrendale, PA 15086-7528,
USA, Minerals, Metals and Materials Society (TMS).
Recrystallization kinetics of hot rolled aluminum alloy is analyzed from the
indirect method of micro-hardness test and direct method of microstructural
evolution using Electron Back Scattered Diffraction (EBSD) in an SEM.
Isothermally annealed samples of hot rolled aluminum alloy were studied
using JMAK type analysis to see if there exists any correlation between the
two methods on analysis, differing in the scale of observation. A good
agreement between the two methods is clearly indicated by similar numerical
values of kinetics parameters from the two methods. Alloy: 1050.
62.
Alvi, M. H., S. Cheong, et al. (2003). Formation of surface
recrystallization of Al-Mg-Si alloy during extrusion. Metallurgical Modeling
for Aluminum Alloys. Proceedings from Materials Solutions Conference 2003.
1st International Symposium on Metallurgical Modeling for Aluminum Alloys,
Pittsburgh, PA, USA, ASM International.
The evolution of texture as a function of recrystallization has been
characterized for hot-rolled AA1050. Samples prepared from a hot rolled
sheet were annealed isothermally for sufficient time to allow complete
recrystallization. The spatial orientation variation within the deformed
microstructure of nucleation, growth and orientations of recrystallized
grains is examined. The microstructural variation and texture evolution in
the samples is observed by automatic indexing of Electron Back Scatter
Diffraction (EBSD) patterns in a Scanning Electron Microscope (SEM). The
effect of deformation texture on the evolution and growth of various
recrystallization texture components is also analyzed by EBSD The analysis
is aimed at obtaining a correlation between the deformation microstructure,
texture development and recrystallization kinetics in the hot-rolled
condition.
63.
Alvi, M. H., S. Cheong, et al. (2003). Microstructural evolution during
recrystallization in hot rolled aluminum alloy 1050. Materials Solutions
Conference 2003, Pittsburgh, PA, USA, ASM International.
The evolution of texture as a function of recrystallization has been
characterized for hot-rolled AA1050. Samples prepared from a hot rolled
sheet were annealed isothermally for sufficient time to allow complete
recrystallization. The spatial orientation variation within the deformed
microstructure of nucleation, growth and orientations of recrystallized
grains is examined. The microstructural variation and texture evolution in
the samples is observed by automatic indexing of Electron Back Scatter
Diffraction (EBSD) patterns in a Scanning Electron Microscope (SEM). The
effect of deformation texture on the evolution and growth of various
recrystallization texture components is also analyzed by EBSD The analysis
is aimed at obtaining a correlation between the deformation microstructure,
texture development and recrystallization kinetics in the hot-rolled
condition.
64.
Alvi, M. H., S. Cheong, et al. (2004). "Texture-dependent
recrystallization in 1050 and 5005 aluminum." JOM 56(11):
2-3.
Recrystallization kinetics have been studied in hot rolled 1050 and 5005
with the objective of understanding the local variation in the rate of
recrystallization as a function of texture component. The overall objective
is to decrease annealing times by exploiting such variations. Automated
electron back-scatter diffraction (EBSD, or OIM) has been used to quantify
microstructures at various stages of recrystallization. Analysis of the
grain orientation spread (GOS) was found to be the most effective method for
partitioning EBSD maps into recrystallized and unrecrystallized regions. The
greatest density of nuclei is observed in the S texture component and the
recrystallization kinetics are consequently fastest in grains that have this
orientation. The cube component is weak in the as-deformed state but
increases to between 25% and 40%, depending on annealing temperature. In
related work, we are using these experimental results to validate a computer
model of recrystallization.
65.
Alvi, M. H., S. Cheong, et al. (2004). Recrystallization and Texture
Development in Hot Rolled 1050 Aluminum. Second Joint International
Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M,
Annecy, France, Trans Tech Publications Ltd.
The evolution of texture as a function of recrystallization has been
characterized for hot-rolled AA1050. Samples prepared from hot-rolled sheet
were annealed isothermally for sufficient time to allow complete
recrystallization. The microstructural variation and texture evolution in
the samples was observed by automatic indexing of Electron Back Scatter
Diffraction (EBSD) patterns in a Scanning Electron Microscope (SEM). The
spatial orientation variation within the deformed microstructure of
nucleation, growth and orientation of recrystallized grains was examined.
The orientation spread within grains was found to be a useful quantity for
partitioning recrystallized and unrecrystallized regions. Also the effect of
deformation texture on the evolution and growth of various recrystallization
texture components was analyzed. The analysis is aimed at obtaining a
correlation between the deformation microstructure, texture devlopment and
recrystallization kinetics in the hot-rolled condition. Preliminary results
suggest only a weak correlation between the rate of recrystallization and
the deformation texture component.
66.
Alvis, R. and D. J. Dingley (1996). Energy Filtering for Electron
Back-Scattered Diffraction Patterns. USA, Advanced Micro Devices, Inc.,
Sunnyvale, California, USA.
A sample to be analyzed by a scanning electron microscope is held at an
electrostatic potential higher than the recording plate of the microscope.
This provides that electrons scattered from the sample which are at an
energy level lower than a chosen level are drawn back into the sample by the
potential of the sample, while other, higher energy scattered electrons
reach the recording plate to form a pattern thereon
67.
Alvis, R., D. J. Dingley, et al. (1995). Observation of Grain Superstructure
in Thin Aluminum Films by Orientation Imaging Microscopy. Microscopy and
Microanalysis.
68.
Alvis, R., D. J. Dingley, et al. (1995). Observations of Thin Films by
Orientation Imaging Microscopy. Microscopy and Microanalysis, Jones and
Begall Publishing.
69.
Amouyal, Y., E. Rabkin, et al. (2005). "Correlation between grain
boundary energy and geometry in Ni-rich NiAl." Acta Materialia
53(14): 3795-3805.
The relative energies of 43 different large angle grain boundaries in
Ni-rich NiAl have been determined with the aid of scanning probe microscopy
using the thermal grooving method at 1400 °C. Simultaneously, the
geometrical degrees of freedom of the same grain boundaries have been
characterized by a combination of electron back-scattering diffraction and
serial sectioning techniques. The determined values of the ratio of the
grain boundary to surface energy are scattered over a wide range of
0.2–1.1. It is found that twist grain boundaries exhibit higher
energies than their tilt counterparts. Moreover, mixed grain boundaries with
approximately equal amount of tilt and twist components do not exhibit high
energies. A strong dependence of the energy of a large angle grain boundary
with fixed misorientational degrees of freedom on its plane inclination has
been demonstrated. The energies of several selected grain boundaries and
free surfaces in NiAl have been calculated by employing an embedded-atom
method (EAM) interatomic potential specially developed for NiAl. The range
of possible relative grain boundary energies estimated from these
calculations is in a good agreement with experimental data.
70.
An, J.-K., J.-Y. Cho, et al. (2005). "Texture investigation of copper
interconnects with a different line width." Journal of Electronic
Materials 34(1): 53-61.
To understand the effect of line width on textural and microstructural
evolution of Cu damascene interconnect, three Cu interconnects samples with
different line widths are investigated. According to x-ray diffraction (XRD)
results, the (111) texture is developed in all investigated lines. Scattered
{111}<112 > and {111}<110> texture components are present in
0.18-μm-width interconnect lines, and the {111<110> texture was
developed in 2-μm-width interconnect lines. The directional changes of
the (111) plane orientation with increased line width were investigated by
XRD. In addition, microstructure and grain-boundary character distribution
(GBCD) of Cu interconnect were measured using electron backscat-tered
diffraction (EBSD) techniques. This measurement demonstrated that a
bamboo-like microstructure is developed in the narrow line, and a
polygranular structure is developed in the wider line. The fraction of
Σ3 boundaries is increased as the line width increases but is
decreased in the blanket film. A new interpretation of textural evolution in
damascene interconnect lines after annealing is suggested, based on the
state of stress and growth mechanisms of Cu deposits.
71.
An, S.-J., J.-Y. An, et al. (2004). The effect of deformation temperature on
the recrystallization behavior of AISI 304 stainless steel. Fifth Pacific
Rim International Conference on Advanced Materials and Processing PRICM-5,
Beijing, China, Trans Tech Publications.
This paper presents a study for constitutive equation over a wide range of
temperatures (700.1100 degrees C) when AISI 304 stainless steel undergoes
large strain. Dependency of flow stress upon strain rate and temperature, is
described by the hyperbolic sine form of the Arrhenius equation. By
modifying the Voce's equation, a constitutive equation for the steel was
obtained. The material constants required in the proposed constitutive
equation have been obtained by a series of hot torsion tests. Also, in this
work, we propose no-dynamic recrystallization temperature (Tndrx) for AISI
304 stainless steel. The Tndrx of the steel is found to be about 855 degrees
C, which can be obtained from continuous cooling torsion (CCT) curve and
electron back-scattered diffraction (EBSD) analysis. Results revealed the
proposed constitutive equations could predict flow stress softening due to
dynamic recrystallization, with an acceptable amount of error, when the
steel undergoes large strain at a wide range of temperatures.
72.
Anderson, I. M., L. A. Tietz, et al. (1992). Interface Structure of Iron
Oxide Thin Films Grown on Sapphire and Single-Crystal MgO. Materials
Research Society Symposium Proceedings, Boston.
73.
Anderson, I. M., M. G. Norton, et al. (1991). TEM Study of Thin Iron Oxide
Films Deposited By Pulsed-Laser Ablation. 49th Annual Meeting of the
Electron Microscopy Society of America.
74.
Anderson, P. A., C. E. Kendrick, et al. (2005). "(111) and (100) YSZ as
substrates for indium nitride growth." Physica Status Solidi C
2(7): 2320-2323.
Wurtzite and zincblende InN have been grown on (111) and (100) oriented YSZ
respectively using a PAMBE technique. Despite a 3D growth mode, the Hall
mobility, carrier concentration and PL intensities in the case of (111) YSZ
substrates surpassed that commonly obtained using sapphire substrates. An
unexpected Hall mobility dependence on growth temperature was identified for
both orientations. (111) YSZ shows promise as an alternative to sapphire,
which may enable device quality InN to be achieved. XRD and EBSD
measurements on the (100) films identified both the zincblende and wurtzite
phases as present within the films. Analysis of the RHEED suggests the film
nucleates in the cubic phase but as growth progresses the wurtzite phase
forms and grows to dominate the film.
75.
Andiarwanto, S., H. Miura, et al. (2002). Dynamic Recrystallization at
Triple Junction during High-Temperature Deformation in Copper Tricrystal.
ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.
Dynamic recrystallization (DRX) at triple junction in copper tricrystal was
investigated during high-temperature tensile deformation. DRX nucleation
occurred preferentially at triple junction at lower strain than the peak
strain (about 2/3). Preferential occurrence of DRX nucleation at triple
junction is considered as a result of stress and deformation concentration.
Most of DRX grains were twin. DRX nucleation process at the triple junction
was discussed in relation to grain-boundary sliding, fold formation and
grain-boundary migration.
76.
Angelescu, D. E., C. K. Harrison, et al. (2003). "Orientation imaging
microscopy in two-dimensional crystals via undersampled microscopy."
Applied Physics A 78: 387-392.
A novel microscopy analysis technique is presented, with applications in
imaging two-dimensional grains and grain boundaries. The method allows the
identification of grain shapes and orientations from large area micrographs,
via the moiré pattern obtained in a raster image. The observed
moiré pattern originates from the aliasing between a
micrograph’s regular sampling raster and the inherent periodicity of
the elements forming the grain under study. The technique presented is very
general, allowing grain analysis via many types of microscopy. We
demonstrate it in this paper by using Tapping Mode Atomic Force Microscopy
and Scanning Electron Microscopy on diblock copolymer thin films.
77.
Anselmino, E., A. Miroux, et al. (2005). In-situ Observations of
Recrystallisation in AA3103 using FEG-SEM and EBSD. 9th International
Conference on Aluminium Alloys, Brisbane, Australia, Institute of Metals and
Materials Australasia Ltd.
Four different samples of AA3103 have been prepared with different secondary
phase particles and Mn solute level and hot deformed in plane strain
compression to simulate hot rolling. In-situ observations of
recrystallisation have been followed in a Field Emission Gun Scanning
Electron Microscope equipped with hot stage. Details of single
recrystallising grains and grain boundaries have been isolated and analysed.
Each grain was found to have its own incubation time for recrystallisation,
velocity and boundary mobility. Evidence of particles and solutes
influencing the grain boundary movement is analysed and commented
upon.
78.
Aplen, M., P. S. Aplin, et al. (1993). "Growth and Characterization of
Electro-deposited Cu/Cu-Ni-Co Alloy Superlattices." Journal Magnetics
and Magnetic Materials 126: 8-11.
79.
Appel, F. and C. Buque (2004). Microstructural aspects of diffusion bonding
of high niobium containing gamma TiAl-based alloys. Gamma Titanium
Aluminides 2003, San Diego, California, USA, Minerals, Metals and Materials
Society.
This paper describes the grain structure, phase morphology, crystallographic
texture, and elemental distribution in the interdiffusion zone of diffusion
bonded couples of a binary titanium aluminide alloy of composition Ti-45Al
(at.%). The results are compared with those obtained on Ti-45Al-10Nb (at.%)
representing a new generation of TiAl alloys with enhanced high-temperature
capability. The studies have been performed on a scanning electron
microscope utilizing electron back-scattered diffraction (EBSD) and energy
dispersive X-Ray analysis (EDX). The micromechanisms responsible for the
microstructural changes occurring in the bonding zone will be discussed with
regard to the phase transformations and diffusion processes
involved.
80.
Apps, P. J. and P. B. Prangnell (2004). Grain refinement mechanisms
operating during severe deformation of aluminium alloys containing
second-phase particles. Ultrafine Grained Materials III (as held at the 2003
TMS Annual Meeting), Charlotte, North Carolina, USA.
The effects of coarse second-phase panicles (Al13Fe4),
and fine coherent dispersoids (Al3Sc), on the evolution of
ultra-fine grained structures have been examined in simple model aluminium
alloys deformed by ECAE. The microstructural evolution has been studied
using high-resolution EBSD and compared to previous work on single-phase
alloys. It is shown that the presence of coarse particles dramatically
increases the rate of grain refinement, and allows a uniform fine grain
structure to be developed at a strain of similar to 5. In contrast, the
presence of fine dispersoids inhibits the formation of new high-angle grain
boundaries at low strains and retards the formation of a fine grain
structure after severe deformation (ε-10). The micro structural
mechanisms operating in each case are discussed.
81.
Apps, P. J., C. P. Heason, et al. (2003). Ultrafine-grain structures
produced by severe deformation processing. Superplasticity in Advanced
Materials: 8th International Conference on Superplasticity in Advanced
Materials, ICSAM 2003, Oxford, UK, Trans Tech Publications.
Severe deformation processes, such as equal channel angular extrusion,
accumulative roll bonding and asymmetric rolling, have been identified as
having potential for producing bulk ultrafine-grained materials on an
industrial scale. The relative merits of these processes are discussed with
reference to their effectiveness at producing ultrafine-grain structures and
their commercial viability. Key features of the grain refinement mechanisms,
operating in simple, model, aluminium alloys, are illustrated using
quantitative EBSD analysis of the deformed microstructures. The influence of
second phase particles, and the role of the texture evolution are also
discussed.
82.
Apps, P. J., C. P. Heason, et al. (2004). "Grain refinement mechanisms
during severe deformation of aluminium alloys: Effect of material
variables." JOM 56(11): 280.
The evolution of the deformed state during the severe deformation of
aluminium alloys is discussed, focusing on the mechanisms involved and the
effect of important material variables. High spatial and orientation
resolution data is presented, obtained using FEG-SEM EBSD orientation
mapping and Kuwahara filtering. It has been confirmed that microshear bands
are responsible for the majority of new high angle boundary formed at
moderate strains. By studying simple model alloys, it has been found that a
fine initial grain size increases the rate of grain refinement at low
strains, but has little influence at ultra high strains. It has also been
show that coarse second phase particles can greatly accelerate the rate of
grain refinement, whereas fine coherent particles inhibit the rate of grain
refinement. These effects are most noticeable at moderate strains, but still
lead to significant differences in the ultra-fine grain structure at very
high strains (e.g. strain = 10). The development of strong textures has been
found to inhibit, and in some cases, reverse grain refinement.
83.
Apps, P. J., J. R. Bowen, et al. (2003). "The effect of coarse
second-phase particles on the rate of grain refinement during severe
deformation processing." Acta Materialia 51(10):
2811-2822.
The effect of second-phase particles on the rate of grain refinement during
severe deformation processing has been investigated, by comparing the
microstructure evolution in an AA8079 aluminium alloy, containing 2.5 vol.%
of similar to 2 μm particles, with that in a high purity, single-phase,
Al-0.13% Mg alloy, deformed identically by ECAE to an effective strain of
ten. The materials were analysed by high-resolution EBSD orientation
mapping, which revealed that grain refinement occurred at a dramatically
higher rate in the particle-containing alloy. A submicron grain structure
could be achieved by an effective strain of only five in the
particle-containing alloy, compared to ten in the single-phase material. The
mechanisms that contribute to this acceleration of the grain refinement
process are discussed.
84.
Apps, P. J., M. Berta, et al. (2005). "The effect of dispersoids on the
grain refinement mechanisms during deformation of aluminium alloys to
ultra-high strains." Acta Materialia 53(2): 499-511.
Pure copper is deformed by high pressure torsion and the resulting
microstructure is studied. Small structural elements are formed. Their size
decreases with increasing strain and reach a steady-state. The
misorientation between neighbouring structural elements increases with
strain and finally reaches a nearly random distribution. The steady-state
size decreases with increasing pressure and decreasing temperature. The
shape of the elements suggests the continuous formation of new elements
during steady-state deformation. This would be a process similar to dynamic
recrystallisation.
85.
Archuleta, J. A., C. J. Boehlert, et al. (2003). "Initial electron
back-scattered diffraction observations of cerium." Philosophical
Magazine 83(14): 1735-1744.
The first electron back-scattered diffraction Kikuchi patterns and grain
orientation maps were captured for pure γ-phase (fcc) Ce. The sample
preparation technique used for electron back-scattered diffraction
orientation mapping of this surface-reactive metal included ion sputtering
the surface using a scanning Auger microprobe followed by vacuum transfer of
the sample from the scanning Auger microprobe to the scanning electron
microscope. The effect of ion sputtering on the microstructure as well as
preliminary electron back-scattered diffraction micro structural
characterization is presented. Based on the sputtering data, the
room-temperature diffusivity of O in γ-Ce was estimated.
86.
Ardakani, M. G., H. Basoalto, et al. (2003). Characterization and Modelling
of Crystal Rotations during Multiaxial Creep in Single Crystal Superalloys.
Thermec' 2003, Leganés, Madrid, Spain, Trans Tech Publications
Ltd.
Life prediction procedures for single crystal superalloys are largely based
on the interpretation of uniaxial creep and low cycle fatigue data although
turbine blades experience significant multiaxial stresses in service.
Several models that have been proposed to represent the anisotropic creep of
single crystal superalloys have the potential of being extended to
multiaxial loading. It is appreciated that uniaxial stresses in
non-symmetric orientations cause crystal rotations during creep. It is less
well known that multiaxle stressing of symmetric single crystals can also
lead to large crystal rotations that can be spatially heterogeneous. In this
study, creep of the single crystal nickel-based superalloy CMSX-4 with
<001>, <111> and <011> nominal orientations has been
studied at 850° C on cylindrical specimens with circumferential notches
and net-section stresses between 600 and 850 MPa. The predictions of crystal
rotation resulting from creep deformation are compared with the experimental
results as a contribution to validating the model.
87.
Ardakani, M. G., H. C. Basoalto, et al. (2004). "Crystallographic
implications of creep deformation of single crystal superalloys subject to
multiaxial loading." JOM 56(11): 323-324.
Most models of anisotropic creep appeal to two or more active slip systems
to account for the observed creep behaviour as a function of orientation,
stress and temperature. Validation of the models by comparing predicted
crystal rotations for uniaxially loaded off-axis specimens with EBSD
measurements is complicated by the progressive development of triaxial
stresses in nominally uniaxial tests due to geometrical constraints. The
present paper presents a comparison of (i) predictions of creep deformation
in multiaxial stresses, including crystal rotations, from an implementation
of a multiple slip model in ABAQUS via a User Creep Sub-Routine and (ii)
EBSD measurements of the spatial variation in crystal rotation in
circumferentially-notched creep specimens.
88.
Ardakani, M. G., M. McLean, et al. (1999). "Twin Formation During Creep
in Single Crystals of Nickel-Based Superalloys." Acta Materialia
47(9): 2593-2602.
A detailed study has been made of the evolution in orientations of single
crystal nickel-based superalloys creep tested in tension to fracture in the
stress range 200-850 MPa and temperature range 750 - 10508C. Overall
rotations from the initial tensile axis along the gauge length as well as
localized changes in orientation have been evaluated. Specimens of SRR99
with nominal axial orientations of [001], [111] and [011] and of CMSX-4 with
[111] and [011] orientations have been considered. Electron back scattered
diffraction (EBSD) analyses of [011] and [111] crystals tested at relatively
high stresses (>450 MPa) show highly deformed regions (~1 µm
lateral dimension) that are oriented at 60° rotation about <111>.
Transmission electron microscopy (TEM) confirms that this orientation
relationship arises from twinning. These features are not observed for [001]
specimens.
89.
Arenas, F., D. P. Field, et al. (2004). EBSD Crystalochemical Analysis of
(W,V)C Cemented Carbides. Microscopy and Microanalysis 2004, Savannah,
Georgia, USA, Cambridge University Press.
Cemented carbides have been characterized since almost a century ago. They
consist mainly of a matrix of hard phase cemented by a metallic binder in a
proportion according to the application required. Many hardmetal
compositions have been previously studied using a wide range of analytical
techniques such as SEM, TEM, EPMA, XRD, etc. But, even though commercial
carbides with more than one hard phase have been in the market for a long
time now, the study of their microstructural development and the
relationships among the hard phases and between them and the binder are
still a matter of interest.
90.
Arnberg, L., A. Bardal, et al. (1999). "Agglomeration in 2 Semisolid
Type 6082-Aluminum-Alloys." Materials Science and Engineering A
262(1-2): 300-303.
91.
Arnould, O., O. Hubert, et al. (2004). Abnormal grain growth effects on the
mechanical behavior of Ni electrodeposits. Second Joint International
Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M,
Annecy, France, Trans Tech Publications Ltd.
The study deals with the long-term reliability of a high precision pressure
sensor using bellows. They are mainly made of electroplated Ni whose thermal
stability is investigated by DSC. EBSD measurements and SEM observations
give some evidence for an abnormal grain growth mechanism whose effects on
the elasto-plastic properties of the Ni deposit are experimentally
investigated. Abnormal grain growth leads to an increase in the elastic
modules and a strong decrease in the yield strength. (Substrate: copper
plated aluminum.)
92.
Asano, T., N. Higashi, et al. (2006). "Location and orientation control
of Si grain by combining metal-induced lateral crystallization and excimer
laser annealing." Japanese Journal of Applied Physics Part 1
45(5 B): 4347-4350.
A new technique of controlling the location and orientation of Si grain by
combining metal-induced lateral crystallization (MILC) and excimer laser
annealing (ELA) is proposed. A starting amorphous Si (a-Si) film is
deposited on a SiO2 substrate having shallow pits. MILC is used
to crystallize the a-Si film in a highly oriented polycrystal. ELA is used
to recrystallize the highly oriented polycrystalline Si film. ELA produces
large Si grains at the shallow pit sites because temperature gradient is
generated by slanting Si surface on the slope of the pit. Si grains whose
size is approximately 1.6 µm were formed at the pit sites. Electron
backscatter diffraction pattern (EBSP) analysis showed that the crystal
orientation aligned over the grain boundary.
93.
Asaro, R. J., F. Gregori, et al. (2006). Mechanical behavior and
microstructural evolution in ECAP copper. 2006 TMS Annual Meeting, San
Antonio, Texas, USA.
The microstructural evolution during ECAP has been investigated using TEM
and EBSD Quasi-static compression and tensile tests, dynamic compression
tests using Reverse Taylor geometry were carried out on ECAP samples after
different number of passes (initial, 2, 4 and 8); the results are
interpreted in terms of the microstructure. Saturation in hardness after 10
ECAP passes is shown to exist indicating a lower limit to the grain size
that can be achieved using this technique (similar to 200-500 nm). The
dynamic response is modeled by means of the Johnson-Cook constitutive
relationship which successfully predicts the shape of deformed specimens and
overall strain and an increased strain-rate sensitivity. The evolution of
the microstructure leading to a steady-state grain size which recomposes
itself as deformation proceeds is discussed. The results suggest a mechanism
for plastic deformation involving dislocation generation and annihilation at
the grain boundaries coupled with grain-segment rotations enabling continued
plastic deformation at a steady state grain size.
94.
Ashton, M. J. and F. J. Humphreys (2004). Inhomogeneous Deformation and
Microstructural Evolution during the Hot Deformation of Al-4.98%Mg. Second
Joint International Conference on Recrystallization and Grain Growth, ReX
& GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
Plane strain channel die compression (PSC) deformation has been carried out
on Al-Mg alloys with Mg contents of 0.1 to 5% at 350 degrees C, and the
deformed microstructures characterised by channelling contrast backscattered
electron imaging (BSE), secondary electron imaging (SE) and high resolution
electron backscatter diffraction (EBSD). Measurements of orientation spread
and misorientation gradient obtained from EBSD maps have been used to
quantify the microstructural inhomogeneity developing in the 4.98% Mg alloy.
The results are consistent with inhomogeneous plasticity with more
deformation occurring in the grain boundary regions. In-situ FEGSEM hot
deformation experiments on the Al-4.98% Mg alloy have provided evidence of
stress driven boundary migration at low strains.
95.
Atkinson, H. V. and S. C. Hogg (2005). "Inhibited coarsening of a
spray-formed and extruded hypereutectic aluminum-silicon alloy in the
semisolid state." Metallurgical and Materials Transactions A
36A(1): 149-159.
The microstructural evolution of a spray-formed and extruded hypereutectic
aluminum-30 pct silicon-5 pct copper-2 pct magnesium alloy heated into the
semisolid state has been investigated. Liquid is formed initially by a
quaternary eutectic reaction and then by a ternary melt reaction. These
reactions occur relatively quickly. However, the binary Al-Si eutectic melt
reaction takes a significant time - around several hours depending on the
temperature. The coarsening rate constants (K) for the growth of the silicon
particles are approximately three to four orders of magnitude lower than
those for the majority of metal spray-formed alloys. This may be associated
with difficulties in addition or removal of atoms from the low index silicon
facets. Where growth does occur, agglomeration of silicon particles may play
a large role, especially at higher liquid contents. Electron backscatter
diffraction (EBSD) gives evidence of agglomeration, and furthermore shows
that high-angle silicon-silicon boundaries are not wetted with
liquid.
96.
Autrata, R. and J. Hejna (1991). "Detectors for Low Voltage Scanning
Electron Microscopy." Scanning 13: 275-287.
97.
Avromovic-Cingara, G., K. T. Aust, et al. (1995). "Superplasticity and
Grain Boundary Distribution in Overaged Al-Li-Cu-Mg-Zr Alloy." Canadian
Metallurgical Quarterly 34(3): 265-273.
98.
Ayer, R., R. R. Mueller, et al. (2006). "Electron backscattered
diffraction study of cleavage fracture in pure iron." Materials Science
and Engineering A 417(1-2): 243-248.
EBSD studies were performed to explore the potential of trace analysis to
determine the crystallography of cleavage fracture plane and planar defects
that form during cryogenic fracture of pure iron. Single- and double-surface
trace analysis revealed that cleavage occurred along the cube {1 0 0}
planes. In addition, using EBSD we were able to identify the planar defects
that formed during fracture to be twins on {1 1 2} planes. The combination
of trace analysis and orientation mapping was able to uniquely identify the
specific variants of the {1 1 2} planes associated with each set of twins.
The twin/matrix interface was mostly scalloped suggesting that twin
formation could be the result of twinning on multiple twin planes.
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