bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Stress-Strain Behavior of AZ91 Alloy at High-Strain Rate
Authors: Sha Gui Ying , Han En-Hou , Xu Yong Bo , Liu Lu
Published: March 2009

The dynamic stress-strain behavior of the AZ91 alloys in different treatment conditions
(as-cast, T4 and T6) was investigated by means of split Hopkinson pressure bar. It was found that the
flow stress increased at first, and then declined with the strain rate increasing at the range of
102~103s-1 for the alloys in these three conditions. And the alloys exhibited both positive and negative
strain rate effects. The former was caused by strain rate strengthening and the latter was caused by
strain rate weakening. However the flow stress for the alloy in aged condition at the same strain rate
was higher than both of the alloys in as-cast and solution conditions. The study also showed that the
maximum strains of the alloys in different conditions increased with the strain rate increasing, and the
strain rate to fracture for the alloy in solution condition was higher than those of other two alloys. The
work-hardening of α–Mg matrix and the reinforcement of β-Mg17Al12 phases led to the strengthening
of the alloy, while thermal softening of matrix, the fracture of β phases and initiation and propagation
of the cracks were responsible for the weakening of the alloy.
Investigation on Wear Resistance of Al-Si-Ti Piston Alloys Produced by Electrolysis
Authors: Xie Jing Pei , Wang Jie Fang , Wang Ai Qin , Wang Wen Yan , Li Ji Wen , Liu Zhong Xia
Published: March 2009

The wear resistance, microstructures, worn surface morphology, TiAl3 phases, eutectic Si
particles and the high density of dislocations of the Al-Si-Ti piston alloys have been studied by means
of SEM and TEM. The electrolytic low-titanium aluminium alloys were used to make the Al-Si-Ti
pistons alloy, the experiment results showed that the wear resistance of the Al-Si-Ti alloy was 1.49
times of that of the Al-Si alloy, and the wear mechanism was mainly plastic deformation wear. The
relationship between wear resistances and the yield strength of the Al-Si-Ti piston alloys were
established, and the wear mechanism investigated by mean of plastic-elasticity theory. When Ti
content is reached to 0.12%, the yield strength of the Al-Si-Ti piston alloy increased from 255 Mpa to
358 Mpa.
Microstructure and Thermal Stability of Al-Mg-Mn Alloys by Equal Channel Angular Pressing at Elevated Temperature
Authors: Ning Jiang Li , Jiang Da Ming , Qian Bing Yu , Fan Xi Gang , Zhang Bao You , Yu Jie , Zhang Xin Mei
Published: March 2009

Two Al-Mg-Mn alloys having similar compositions but with and without Zr addition were
subjected to equal channel angular pressing (ECAP) at 350°C using route BC and a 90° die, followed
by water quenching or air cooling. A series of annealing experiments were conducted at various
temperatures from 400°C to 460°C on the water-quenched alloys. Fine structures with grain size of
approximately 1~2μm were obtained in these alloys after 6 passes. The water-quenched alloy
containing Zr exhibited finer structure compared with the Zr-free alloy in the same cooling condition,
which was due to the existence of Al3Zr dispersoids. And in the air cooling condition, it was found
that in the Zr-free alloy static recovery occurred, and in partial regions some small grains without
dislocation inside appeared suggesting the occurrence of static recrystallization. This demonstrated a
fairly restored structure. However, the microstructure of the alloy containing Zr kept stable during the
air cooling process. In addition, in the annealing experiments, secondary recrystallization took place
in the Zr-free alloy annealed at 410°C for 1h, while the alloy containing Zr kept stable up to 460°C.
TEM observation showed that the Al3Zr dispersoids pinned the motion of the grain boundaries,
thereby the secondary recrystallization and grain growth were inhibited.
Microstructure Evaluate System of Semi-Solid Forming
Authors: Cui Xiao Peng , Liu Yong Bing , Cao Zhan Yi , Zhang You Fa , Zhang Qian Qian
Published: March 2009

The evaluating rules for semi-solid microstructure were brought up, and the analysis
software was developed on MATLAB 7.0 platform in this study. Furthermore, this system can be used
not only in the Thixomolding AZ91D magnesium alloy microstructure analysis, but also in the other
semi-solid processing microstructure.
Morphology and Distribution of in Al-Fe Alloy under an Alternating Magnetic Field
Authors: Han Yi , Ban Chun Yan , Guo Shi Jie , Ba Qi Xian , Cui Jian Zhong
Published: March 2009

The aim of this work is to study the effect of a low frequency alternating magnetic field on
morphology and distribution of A3F2 in the Al-2.89 wt.% Fe alloy. At the cooling rate of 0.05 °C/s,
only Al3Fe phase was observed in the iron-containing intermetallics. It was noteworthy that,
compared with the conventional solidification, the primary Al3Fe phase was refined and accumulated
towards the center of the sample by applying the alternating magnetic field. This phenomenon is
considered as the result of the larger Lorentz force acting on the Al3Fe phase than the Al matrix.
Effects of Titanium Refining Methods on the Microstructure and Mechanical Properties of A356-0.1%Ti Alloys
Authors: Li Ji Wen , Xie Jing Pei , Liu Zhong Xia , Wang Wen Yan
Published: March 2009

Effects of titanium refining methods on the microstructure and mechanical properties of
A356 alloys were studied. The results showed that the A356 alloys refining by electrolytic low
titanium Al alloys had excellent grain refinement effect and high age-hardening behavior comparing
with the traditional A356 alloys. By means of DSC analyses, the solidification characteristics and the
age-hardening behavior were discussed. The results showed that the E-A356 alloys had more
powerful nucleation potency than that of the M-A356 alloys. The exothermic peaks of β// phase was
shifted to a slightly lower temperature, and the rate of the continuous transition from GP zone to
metastable phases increased.
The Relative Importance of Nucleation vs. Growth for Recrystallisation in Particle-Containing Fe3Al Alloys
Authors: Kobayashi Satoru , Zaefferer Stefan , Raabe Dierk
Published: March 2009

Recrystallisation behavior was studied in two Fe3Al-based alloys containing both large and
fine particles with a different fine particle dispersion level using high-resolution SEM and EBSD.
High misorientation of 15-30° was created around large particles after a hot rolling process in the two
alloys. The kinetics of recrystallisation were, however, considerably retarded in the alloy containing
dense fine particles. It was observed that the growth of subgrains created around the large particles
was inhibited by the presence of the fine particles. This result clearly suggests that when the particle
density (Ns) is high relative to local stored energy (E) around large particles, nucleation can be
completely hindered. As the Ns/E level decreases, nucleation may occur and the kinetics of
recrystallisation might be determined by both the nucleation rate and the growth of nuclei into a
matrix with fine particles.
Microstructural Refinement during Annealing of Plastically Deformed Austenitic Stainless Steels
Authors: Herrera C. , Plaut R.L. , Padilha Angelo Fernando
Published: March 2009

The phenomena of strain hardening, strain induced martensite formation, recovery, martensite reversion and recrystallization have been studied in austenitic stainless steels of the AISI 304L and 316L types, after solution annealing, followed by rolling at different temperatures (-196, 25, 100 and 200°C) and subsequent annealing of the worked samples. Strain hardening and the percentage of α’ martensite formed showed strong dependency with the deformation temperature and with the austenite chemical composition. As expected, both strain hardening as well as the amount of the martensite formed was higher in the 304L steel and for lower temperatures. Reversion temperature of the α’ martensite was close to 550°C for both steels, independent of the amount of martensite. The 316L steel presented a higher resistance to recrystallization when compared to the 304L steel. The recrystallization temperature of both steels was about 150°C higher than the α’ phase reversion temperature. Rolling temperature did not influence significantly the recrystallization temperature. Proper thermal and mechanical treatments lead to interesting combinations of mechanical properties in both steels with values such as yield strength YS of about 1000 MPa, with an elongation around 10%.
In-Situ EBSD Observation of the Recrystallization of an IF Steel at High Temperature
Authors: Nakamichi Haruo , Humphreys John F. , Bate Pete S. , Brough Ian
Published: March 2009

Recrystallization phenomena in an interstitial free (IF) steel have been investigated by
in-situ annealing in the SEM, combined with Electron Back Scattered Diffraction (EBSD) mapping.
Sequential recrystallization phenomena, such as initiation and growth of new grains, are clearly
distinguished by EBSD mapping at temperatures of up to 1070K. More than 70% of the recrystallized
grains are of {111}<121>, {111}<123> and {111}<110> orientation. It is found that many
recrystallized grains are formed from {111}<123> deformed grains at the beginning of
recrystallization. It is observed that some of α-fibre (RD//<110>) orientations have difficulty in
recrystallization compared to γ–fibre deformed grains. In particular, many grains of {001}<110>
orientation remain un-recrystallized even after holding for 65 minutes at 1050K.
The Effects of Hot Band Annealing Temperature on the Texture of 2%Si Nonoriented Electrical Steel
Authors: Choi Jae Young , Park Chel Min , Park Jong Tae , Kim Jae Kwan
Published: March 2009

The effects of hot band annealing temperature on the texture of the 2%Si nonoriented electrical steel were investigated. Slab was hot rolled and then hot band annealed in the temperature range of 900°C~1100°C. The magnetic flux density and the core loss were improved by the hot band annealing because of the texture improvement. As the hot band annealing temperature was increased, the magnetic properties were improved. The microstructure of the hot band was composed of a recrystallized structure at the surface and a deformation structure near the middle plane. These hot bands were completely recrystallized after annealing above 1000°C. The main texture of the hot band was rotated cube and gamma-fibre. After hot band annealing, rotated cube changed to cube texture and gamma-fibre intensity gradually decreased. In the case of non-annealed hot band, rotated cube in the middle plane was changed to near {111}<112>texture and Goss texture in the surface to gamma fibre after final annealing. In the case of the hot band annealed at 900°C, rotated cube near the middle plane changed to Goss texture and Goss texture in the surface to rotated cube after final annealing. After final annealing, the {111} and {112} texture was dramatically decreased as the hot band annealing temperature was higher. The total {100} texture intensity was not changed. Cube texture {100}<001> increased and rotated cube texture {100}<011> decreased. The {110} texture increased after hot band annealing irrespective of temperature. As the hot band annealing temperature was higher, the Goss texture increased, and this increase of Goss texture causes the anisotropy of the magnetic flux density.
Microstructure Evolution during Thermal Processing : Insight from In-Situ Time-Resolved Synchrotron Radiation Experiments
Authors: Bednarčík J. , Nicula R. , Saksl Karel , Stir M. , Burkel E.
Published: March 2009

The magnetic, mechanical or chemical properties of nanocrystalline materials strongly
differ from the ones of their coarse-grained counterparts. Moreover, significant changes of the phase
diagrams were already evidenced for nanostructured alloys. Thermal processing with or without
applied pressure controls the microstructure development at the nanometer scale and thus essentially
decides upon the final nanomaterial behaviour and properties. A common route for the synthesis of
metallic nanomaterials is the devitrification of amorphous precursors obtained via non-equilibrium
processing, e.g. by rapid solidification or high-energy ball-milling. Time-resolved in-situ X-ray
diffraction experiments may nowadays be performed at high-brilliance synchrotron radiation
sources for a variety of temperature-pressure conditions. The temperature-time evolution of the
grain-size distribution and microstrain can be monitored in detail at specimen-relevant scales.
Together with local information from electron microscopy and chemical analysis, in-situ X-ray
experiments offer a complete set of tools for engineering of the microstructure in nanomaterials.
The effect of individual processing steps can be distinguished clearly and further tuned. An example
is provided, concerning the high-temperature microstructure development in Co-rich soft magnetic
nanostructured alloys.
Three Dimensional Microstructure–Microtexture Characterization of Pipeline Steel
Authors: Petrov Roumen H. , García Orlando León , Mulders J.J.L. , Reis Ana Carmen C. , Bae Jin Ho , Kestens Leo , Houbaert Yvan
Published: March 2009

The microstructural anisotropy together with the crystallographic texture of an industrial
grade of X70 pipeline steel is studied by means of the 3D-EBSD technique known also as EBS3
which was recently developed by FEI. Samples of size 8x10x3mm³ were cut from the middle thickness
of an industrial rolled plate and after special sample preparation have been studied in a Nova
600 dual beam scanning electron microscope equipped with a field emission gun and HKL Channel
6 EBSD data collection software for crystallographic orientation, which allows multiple sectioning
of the sample in automatic mode and, afterwards reconstruction of both the 3D microstructure and
texture of the examined volume. Three scanned zones of different volumes that varied between
15x10x27 4m³ and 16x14x6 4m³ have been examined and the results for the crystallographic orientation,
grain shape and grain shape orientation are discussed together with the data for the anisotropy
of the Charpy impact toughness of the material.
Forming Limit Diagrams for AA5083 under SPF and QPF Conditions
Authors: Kulas Mary Anne , Krajewski Paul E. , Bradley John R. , Taleff Eric M.
Published: March 2009

Forming Limit Diagrams (FLD’s) for AA5083 aluminum sheet were established under
both Superplastic Forming (SPF) and Quick Plastic Forming (QPF) conditions. SPF conditions
consisted of a strain rate of 0.0001/s at 500°C, while QPF conditions consisted of a strain rate of
0.01/s at 450°C. The forming limit diagrams were generated using uniaxial tension, biaxial bulge, and
plane strain bulge testing. Forming limits were defined using two criteria: (1) macroscopic fracture
and (2) greater than 2% cavitation. Very little difference was observed between the plane strain limits
in the SPF and QPF conditions indicating comparable formability between the two processes with a
commercial grade AA5083 material.
Superplasticity of Ultrafine-Grained Aluminum Alloy Processed by ECAP and Warm Rolling
Authors: Islamgaliev Rinat K. , Yunusova N.F. , Bardinova M.A. , Kilmametov A.R. , Valiev Ruslan
Published: March 2009

The ultrafine-grained (UFG) 1421 aluminum alloy processed by equal channel angular
pressing (ECAP) has demonstrated enhanced superplasticity at low temperature and high strain rates.
This UFG material was successfully rolled at temperatures of 330-370oC retaining small grain size
and equiaxed grain structure. The microstructure of the UFG alloy subjected to warm rolling (WR)
was studied, and the mechanical properties of the ECAP+WR samples with UFG structures were
investigated. We have found that the rolled material exhibited not only the enhanced superplasticity,
but also high strength at room temperature.
Study on the Interface Characteristic of Superplastic Diffusion Bonding Joint of Dissimilar Steels
Authors: Wang Min , Guo Hong Zhen
Published: March 2009

Magnesium alloys show promise in meeting the demand for materials of lighter weight and
higher rigidity. Mg alloys are hard to process and normally require grain refining for improved
formability and mechanical properties. To process these fine-grained Mg alloys effectively, it is
important to relate their load stress and mechanical properties to changes in their microstructures.
Using a biaxial tensile machine and cruciform specimens, to evaluate the mechanical properties,
microstructure, and plasticity, in a high temperature biaxial stress state, used of AZ31 Mg alloy sheet.
With biaxial deformation, grain boundary slide occurred more frequently than with uniaxial
deformation, causing grain boundary separation and formation of micro-voids between the grains. In
the vicinity of the cracks and at the locations of grain boundary separation, although deformation
temperature at higher than the recrystallization temperature, fine grains (about 2 μm) showing in
duplex grain structures were formed locally. The formation of duplex grain structures as a result of
local formation of fine grains during the deformation process is a major issue to be solved from the
viewpoint of plasticity processing.
Superplastic Forming and Diffusion Bonding for Four-Layer Sheets Structure of Nickel-Base Superalloy
Authors: Han Wen Bo , Wu D.Z. , Wang Guo Feng , Tong M.J.
Published: March 2009

The superplastic forming and diffusion bonding (SPF/DB) is applied in aviation and space
flight field. The SPF/DB process with gas pressure control for dissimilar superalloy structure was
studied. Diffusion bonding parameters, including bonding temperature T, pressure P, time t, affect the
joining mechanism. When the bonded specimen with 50&m thick nickel foil interlayer was tensile at
room temperature, shear fracture of the joints with nickel foil interlayer takes place at the GH4141
superalloy part. The SPF/DB of four-layer sheets structure was investigated. The optimum parameters
for the SPF/DB process are: forming temperature T=1243K, forming pressure P=1MPa, forming time
t=35min. The microstructure of the bonded samples was characterized. The microstructure shows an
excellent bonding at the interfaces. The distribution of thickness after SPF/DB was investigated.
Superplasticity and Superplastic Formability of Hot-Rolled AZ31 Magnesium Alloy
Authors: Yin D.L. , Wang C.W. , Wang Jing Tao , Yu Yan Dong
Published: March 2009

The superplasticity of a hot-rolled AZ31 Mg alloy was investigated by uniaxial tensile tests
at temperature range 250-450oC and strain rate range 0.7×10-3-1.4×10-1s-1. Superplastic formability of
the alloy was evaluated by gas bulging test at elevated temperatures. The threshold stress for grain
boundary sliding (GBS) was calculated and the topography during superplastic deformation was
observed by SEM. It is found that, at 400 oC and 0.7×10-3 s-1, the maximum elongation reaches
362.5%. GBS is the predominant deformation mechanism and characterized by a pronounced
improvement in homogeneity with increasing temperatures, indicating a transformation of GBS mode
from cooperative GBS (CGBS) to individual GBS (IGBS). The improved homogeneity of GBS can
be interpreted in terms of decreased threshold stress with increasing temperatures. Gas bulging test
demonstrates that the temperature for the best superplastic formability is 400 oC and a hemispherical
part with a specific limiting dome height of 0.51 was obtained, suggesting good application prospect
for this alloy.
Superplastic Behaviors of Casting AZ31 Magnesium Alloy
Authors: Li Hong Bo , Zhao J. , Luo Jun Ting , Hang M.
Published: March 2009

The superplasticity of magnesium alloy is important in industrial application. However
the superplastic deformation of casting magnesium alloy is hard to be realized. In this paper, the
stress–strain behaviors of casting AZ31 magnesium alloy with various strain rates at different
deformation temperatures were investigated. The alloy was tested in the tensile condition with
initial grain size of 25μm. It was found that the elongation of the alloy at 400°C with ε&
= 4.25×10-4
s-1 is almost 200%. According to the results of uniaxial tensile experiment, the alloy exhibited
superplastic deformation behavior with the slow stain rate in a temperature range of 350 to 450°C.
The microstructures deformed and undeformed samples were observed with aid of optical
microscope.
Strain Rate Gradient Model with Couple Stress for Micro Scale Rigid-Viscosity-Plastic Deformation
Authors: Lei K. , Zhang Kai Feng
Published: March 2009

In order to describe scale effects in rigid-viscosity-plastic deformation at micro scale, a
strain rate gradient model with couple stress is proposed. In the constitutive equation, couple stress,
strain rate gradient are introduced on the assumption that the potential energy depends upon the scalar
invariants of the strain rate tensor and strain rate gradient tensor, at the same times, the influences of
length scale of body, grain size and temperature are also considered. A FEM-based program based on
this strain rate gradient model is used to simulate the process of high temperature gas pressure
forming, and the value of length scale 2 l is evaluated by simulation pilot calculation. It is indicated
that rigid-viscosity-plastic deformation can be more accurately simulated by the present strain
gradient rate model as long as the material parameters in constitutive equation are selected suitably.
High-Temperature Deformation Behavior of ELI Grade Ti-6Al-4V Alloy with Martensite Microstructure
Authors: Park C.H. , Ko Young Gun , Lee Chong Soo , Park Kyung Tae , Shin Dong Hyuk , Lee Ho Sung
Published: March 2009

High-temperature deformation behavior and microstructural evolution process of ELI
Ti-6Al-4V alloy having martensite microstructure were investigated with the variation of strain, strain
rate and temperature. A series of hot compression tests was carried out isothermally for martensite
microstructure at the true strain range of 0.6 to 1.4, strain rate range of 10-3 s-1 to 1 s-1 and temperature
range of 700 oC to 950 oC. The processing maps for martensite microstructures were constructed on
the basis of dynamic materials model (DMM). At the strain rate higher than 10-2 s-1 and the
temperature lower than 750 oC regions of flow instability such as adiabatic shear band and
micro-cracking were observed. Also, after imposing an effective strain of ≈ 1.4, deformed
microstructure showed the significant kinking/bending behavior of lamellae resulting in the dynamic
globularization associated with the fragmentation of beta-phase. The effects of strain, strain rate and
temperature for dynamic globularization were discussed based on the microstructure and efficiency of
power dissipation.
Solid State Diffusion Welding by Superplastic Coordinate Deformation between Vacuum Spray Fusing Alloy G111WC and Steel Substrate
Authors: Zhang Yao Zong , Huang Jian Bo , Wang H.P. , Lin X.
Published: March 2009

This paper discusses the issues about the incorruptibility of industrial dies, mainly
researches the G111WC and G112WC mixed alloy layer sprays fusing on the surface of industrial
dies under the vacuum condition and the solid phase welding-on mechanism of the mixed alloy layer
under superplastic state. It points out that when W≈1 ( W is strain ratio of coating and substrate ) and
within the range of the generatrix’s superplasticity, the layer and the generatrix will realize the solid
state diffusion joining by superplastic coordinate deformation, which leads to an effective welding.
Grain Refinement and High Temperature Deformation in Friction Stir Processed Sheets of Magnesium Alloys
Authors: Takayama Yoshimasa , Otsuka Y. , Shibayanagi Toshiya , Kato Hajime , Funami Kunio
Published: March 2009

Grain refinement and high temperature deformation in two kinds of magnesium alloys
subjected to friction stir processing (FSP) have been investigated. One was a rolled sheet of
LA141Mg and another was a cast plate of AZ91Mg. FSP was developed by adapting the concepts of
friction stir welding to obtain a fine grain size in a stirred zone. Grain refinement was achieved by FSP
to give fine grain sizes of 11.4μm and 8.4μm for LA141 and AZ91 alloys, respectively. For LA141
alloy, the maximum stress of the FSPed sample was higher than that of the as-received one in the
range of 300K to 523K while the elongation to failure of the former was considerably smaller than
that of the latter. On the other hand, the elongation for the FSPed sample of AZ91Mg showed three
times larger elongation with a lower maximum stress than the as-received cast one at 523K and
2.8×10-3s-1. Further difference in high temperature deformation for both magnesium alloys was
discussed based on microstructural change and stress-strain curves.
Rheological Analogies of Superplastic and Viscous-Plastic Materials Flow
Authors: Smirnov Oleg M. , Portnoy V.K. , Tsepin M.A. , Lissunets N.L.
Published: March 2009

There are presented original experimental results of studying rheological behavior of
Vitralloy 1 (Zr41Ti14Cu12.5Ni10Be22.5), which shows in the certain strain rate range stable linear
viscous (Newtonian) flow. Comparative analysis of these results and the results related to other
superplastic alloys as well as to crystallizing metallic melts has been carried out.
Application of High-Strain-Rate Superplastic Zn-Al Alloy to Seismic Dampers and its Optimised Shape Design
Authors: Kushibe Atsumichi , Takigawa Yorinobu , Higashi Kenji , Aoki Kazuo , Makii Koichi , Takagi Toshiaki
Published: March 2009

As a new damping material, the authors first developed a Zn-22wt.%-Al eutectoid alloy
with ultra-fine grains exhibiting superplasticity at room temperature by means of thermomechanical
controlling processes (TMCPs). The Zn-Al alloy has a few advantages such as low
work-hardening rate and high ductility over a conventional seismic damping material, for instance, a
low-yield-point steel. In addition, Zn-Al alloys are environment-conscious because of no harmful
metal like Pb. However, when Zn-Al alloys are subjected to plastic deformation, since its work
hardening is small, plastic deformation proceeds locally so that required absorption energy cannot
be sufficiently obtained, and local fracture and local deformation instability can take place easily,
which is the intrinsic characteristic of superplastic materials. Therefore we attempted to develop a
shear panel type, a brace type damper for tall buildings and a bending type damper for Japanese
wooden houses using FEM analysis in order to minimize localized strain and local deformation and
to determine the optimum shape for this Zn-Al superplastic seismic damper. As a result, an
ecological and high-energy absorption seismic dampers, so-called “maintenance-free seismic
damper,” was successfully developed.
Study on Superplastic Grain Growth Model and Dynamic Simulation
Authors: Zhou Tian Rui , Wang L.J. , Xiong C.H.
Published: March 2009

The ability of metal plastic forming and the mechanism performance of the part are
correlated with grain granularity of the metal. Grain growth is a prominent character of the
microstructure evolution. It is very helpful for the design of process and die structure to study the
mechanism of superpalstic deformation and microstructure evolution of superplastic forming. The
microstructure evolution of material is impact directly the mechanic performance of the component in
superplastic forming. It is necessary to optimize the complex process and to predict the microstructure
evolution. A new simulation method that integration the finite element simulation and the
microstructure simulation of superplastic forming is introduced in this paper. Monte Catlo method is
an odds simulating technique and can simulate time course of microstructure evolution. Based on the
studies of superplastic grain growth mechanism, the superplastic grain growth rate equation are
derived in this paper by coupling static state anneal grain growth mechanism and deformation
stimulated grain growth mechanism. The grain growth drive force of superplastic deformation
includes mostly boundary energy and distortion energy. A new drive force model is derived based on
energy model. The microstructure evolution is correlated with the stress and strain of the part, and the
integration of superplastic forming FE simulation and microstructure evolution MC simulation is
realized. Using the integrating simulation technique can predict not only the forming process but also
presenting grain growth image of the part. Experimental studies of the part in forming process and
microstructure evolution were performed.
Microstructure Evolution and Mechanical Properties of Mg Alloy AZ31D Processed by Equal Channel Angular Extrusion
Authors: Zhang Yan Shu , Zeng Zhi Peng , Liu X.F. , Jin Quan Lin
Published: March 2009

The microstructure evolution and mechanical properties of magnesium alloy AZ31D
processed by equal channel angular extrusion(ECAE) are studied. The processing temperature and the
passes of extrusion are important factors to affect the microstructure and mechanical properties of the
magnesium alloy during ECAE. In this paper, ECAE was performed at the temperature from 523 to
673K. The ductility increased through the grain refinement after the ECAE because the
recrystallization took place and high angle grain boundary formed. The elongation of magnesium
alloys AZ31D was improved after the ECAE. The maximum elongation-to-failure of magnesium
alloys AZ31D processed by ECAE for 4 passes at 573K and strain rate of
0.5 10−4 s−1 × was 350%.
Analysis, Planning, Modelling and Presentation of an SPF Model-Plant in Virtual Reality
Authors: Beck Werner , Meynard J. , Ouarraoui A. , Klemkow R.
Published: March 2009

Superplastic forming (SPF) is well known in aircraft production of Titanium and
Aluminium parts. The process technology is commercially interesting for small quantities. The
advantage of low upfront cost for the tooling is quickly lost however in conjunction with the longer
cycle times of forming under purest SPF conditions. At given production rates typical for the aircraft
industry the technology has an economical advantage over conventional, ambient temperature sheet
metal forming processes. Compared to established processes the break-even point is at about 400 to
4000 parts/year, depending on the metal alloy and the geometry. Transfer to high volume production
as afforded by automotive production of niche products calls for a modified forming process and an
optimisation of the production flow. One alternative for a modified process is called “Hot Gas
Pressure Forming” (HGPF). This process is very comparable to SPF, but the applied strain rates are
much higher than recommended for SPF. HGPF can be applied in combination with a pre-forming
operation done by cold or hot forming. The production line which has to be created to establish a
constant production flow of outerbody parts like doors, inner and outer, fenders, bonnet and trunklid,
inner and outer and roof for a project with an annual production quantity of ~30 to 40 000 cars has
been engineered on the basis of the material’s forming behaviour studies, process investigations, cost
analysis studies, etc. The elements of the production line like presses, interstockers, transportation ,
etc have been defined and placed with the help of a production simulation tool to get the best
efficiency combined with suitable flexibility.
Modeling the Longitudinal Temperature Evolution of a Chirped Fiber Bragg Grating Submitted to Temperature Gradients
Authors: Neto B. , André P.S.
Published: March 2009

The chromatic dispersion of optical fiber is a limiting factor in the increase of optical communications transmission bitrates. Chirped Fiber Bragg Gratings submitted to temperature gradients can provide tuneable dispersion compensation, being the tuneability achieved by an appropriate control of the applied temperature gradient. In this work we propose a numerical model that describes heat transfer mechanisms along the fiber grating and its surroundings to obtain a temperature distribution along the fiber grating longitudinal axis. This model, which enables the subsequent modeling of the grating dispersion, demonstrated that the temperature distribution in a steady state is linear. The subsequent modeling of the fiber grating chromatic dispersion agreed with experimental results.
Texture Evolution during High Temperature Plane Strain Compression of High Silicon Steels
Authors: Rodriguez-Calvillo Pablo , Houbaert Yvan
Published: March 2009

High silicon steel is used for electrical applications because its electrical resistivity is
increased and the magnetostriction is reduced. A silicon content up to 6.5 wt.-% gives excellent
magnetic properties. The improvement of the magnetic properties stays in contrast with the lack of
ductility of these alloys, making their thermo-mechanical processing difficult. The optimum final
microstructure and texture depends on the final application of the material: extremely big grains with a
Goss orientation ({110} <001>) are desired in transformers and grains with an average size of 100 -m
and cube component ({100} <001>) are used in electrical motors.
A series of plane strain compression (PSC) tests were performed on 3 electrical steels, with a silicon
content from 1.8 to 4.1 wt.-%, in a temperature range of 800 to 1100°C, strain rates between of 0.5 and
5 s-1. Reductions and time between deformation and quenching were also varied in order to study the
recrystallisation progress. Apparent activation energies for hot working, calculated using the hyperbolic
sine equation, was in good agreement with literature and higher than the activation energy for self
diffusion in iron. These values increase with the silicon content.
The high temperature texture evolution was investigated by means of electron back scattering
Diffraction (EBSD) technique, which allows the quantification of important texture components in
function of the thermo-mechanical parameters applied during hot rolling and the plane strain
compression tests. The hot rolled microstructures have shown an average grain size of 140 -m and a
texture with a maximum on the cube fibre ({001} <-1-10>). The conventional α (<110> // RD) / γ
(<111> // ND) fibre texture was developed after plane strain compression and their intensities depend
on the deformation temperature and reduction. A similar tendency was observed for the fraction of
static recrystallised grains.
Intermediates in Ring-Disc Electrode Processes
Authors: Sequeira César A.C.
Published: March 2009

In the history of electrode processes, intermediates are of extraordinary interest. In the lecture which follows, the most common types of intermediates in electrode processes are classified. Secondly, most of the methods which are available and have been used in finding intermediates are characterised. Thirdly, the principles of detection of intermediate and final products of electrode processes on the basis of kinetic information obtained by means of the rotating ring-disc electrode method are discussed. This approach is used for identification of the products of an organic electroreduction. In conclusion, it is demonstrated that the cathodic reduction of such organic compounds involves formation of stable and unstable intermediates.
Comparison between the Thermodynamical Behaviour of PdTe2 and PtTe2, while Subjected Isothermally to High Pressure
Authors: Grigorova Veneta , Roussev Dimitar , Jobic Stephane
Published: March 2009

In the present paper we studied the thermodynamical behaviour under high pressure of
two MTe2-type compounds (M = Pd, Pt) by applying the thermodynamical method, which we
elaborated in previous studies [1,2]. The two discussed compounds are representatives of the CdI2
structure type, which is bi-dimensional and as such is atypical for the big family of lamellar MQ2-
type dichalcogenides (Q=S, Se, Te). Specific of lamellar structure is the strong ionicity of the
bonds. Its direct consequence is cleavage obtaining, lubrication properties, anisotropic physic
properties. One of the most interesting points stands on the possibility for realising interactions
between the layers of different types of ions. That could be done under high pressure by any of the
following transformation processes: (i) a phase transition to the typical pyrite structure; (ii) a phase
rearrangements changing the parameters of the crystal cell but keeping the 2D-type structure. The
computation of the volumetric thermodynamical functions showed that both PdTe2 and PtTe2 do not
undergo any classical phase transition [1]. But we observed a curious difference in their stability:
PtTe2 loosed its stability quite fast and PdTe2 was quite stable. Aiming to clarify if the difference in
the volumetric entropy generation was due to different phase rearrangements, we calculated the
longitudinal thermodynamical functions. In such a way we detected that both PdTe2 and PtTe2
undergo a phase rearrangement. The change along one of the space axis in both compounds was
compensated by the reverse change along the other space axis. Like this no changes at the
volumetric level were observed. The longitudinal calculations gave an explanation for the
differences in entropy generation at volumetric level: beyond the rearrangement point PdTe2
decreases its entropy generation, i.e. its new arrangement is somehow stable under increasing
pressure. While, beyond its rearrangement point PtTe2 increases its entropy generation, i.e. even in
the new arrangement it loses stability under increasing pressure. We conclude that both PdTe2 and
PtTe2 do not undergo a classical phase transition at volumetric level. At longitudinal level both
compounds undergo phase rearrangement. A difference between PdTe2 and PtTe2 is observed in
their entropy generation beyond the rearrangement point.
Comparison between Self-Consistent and Intermediate Approaches for the Simulation of Large Deformation Polycrystal Viscoplasticity
Authors: M'Guil S. , Ahzi Saïd , Youssef H. , Grácio J. , Khaleel Moe A.
Published: March 2009

In this work, we propose a comparison between two different approaches for the
simulation of the large deformation response and crystallographic texture evolution in polycrystals.
The first approach is the well-know self-consistent scheme. For this, we used the Visco-Plastic-
Self-Consistent (VPSC) approach. The second approach is based on a recently developed
intermediate modeling. In a first part of this paper, we present the VPSC model. In a second part,
we define the intermediate linear modeling which is based on a linear combination of Taylor and
Sachs models using a weight parameter. For the comparison of these two approaches, we present
different results in the case of uniaxial tests for an FCC polycrystal for different values of the
weight parameter for the intermediate modeling and for different formulations of the macroscopic
moduli in the self-consistent model.
Effect of Fibre Heat-Treatment on Nicalon SiC Fibre Reinforced β-SiAlON Matrix Composites
Authors: Demir Adem , Thompson Derek P.
Published: March 2009

Nicalon SiC fibre tows have excellent properties for ceramic matrix reinforcement but residual oxygen within the fibres degrades fibre properties when these are incorporated into ceramic matrices at elevated temperatures. β-SiAlON ceramics also have excellent mechanical and physical properties, especially fracture toughness. However, sintering of β-SiAlON is generally carried out at 1650-1750°C, considerably higher than the temperatures above which fibre degradation occurs (>1200°C). In the present study, the refractoriness and strength of Nicalon fibres were improved by high pressure CO heat treatment, and densification temperatures of β-SiAlON were lowered by using different kinds of sintering additives. Heat-treatment of the fibres under 45 bar CO pressure at 1500-1650°C led to an increase in fibre strength and to the formation of a thin carbon layer on the surface of the fibres. These improvements in the Nicalon SiC fibres allowed them to be incorporated successfully into β-SiAlON matrices. The as-received and heat-treated fibres were infiltrated with β-SiAlON starting powder mixes and hot-pressed with low temperature sintering additives at 1600-1700°C for 30 min. Bending strength and fracture toughness measurements showed that samples containing heat-treated fibres provided a significant strength and fracture toughness increase compared with similar samples prepared using as-received fibres, and massive pull-out was observed because of the weak interface resulting from the surface carbon coating on the fibres.
From Earth Minerals to Nitrides
Authors: Karakus N. , Kurt A.O. , Toplan O.
Published: March 2009

Structural ceramic parts such as those made from Si3N4 or SiAlONs are promising for
considering them in replacing metals in the areas where harsh environmental conditions like
abrasive corrosion under high stresses along with high temperature effects are dominant. A
widespread use of these ceramics depends on the ease of finding them with low cost. This paper
highlights some important points on the low cost production technique of Si3N4 or SiAlON
ceramics in powdered form via carbothermal synthesis technique using minerals in the light of the
current and previous works. The technique gives flexibility of controlling production parameters
that affect on the yield and quality of powders produced. A special account is given to the effects of
reactants on the production of such ceramic powders. After synthesising ceramics in powdered
form, some comparisons were made on the characterisation of the products of homemade ones with
that of commercially available ones. After successful experimental works, a raw material of
orthoclase clay mineral exhibited a high transformation potential to a mixture of Si3N4 and SiAlON
type ceramic powders.
CVD Synthesis of Tungsten Nitride and lts Deposition Behavior
Authors: Nagai M. , Nakaya H.
Published: March 2009

The synthesis and deposition behavior of tungsten nitrides on a Si(400) or quartz
plate were studied using a vertical hot-wall tube reactor. The preparation of the tungsten nitride
by chemical vapor deposition (CVD) is predicted by the sticking probability of tungsten nitride
by calculating the step coverage on the Si(400) engraved with a microtrench of different aspect
ratios. The CVD deposition was performed at temperatures of 556–1063 K for deposition times
up to 45 min in a gas mixture of WF6–NH3–H2 in Ar and at a total pressures of 5 and 13 Pa.
From the XRD analysis, amorphous crystallites were observed at 556 and 673 K but β–W2N
(111) was obtained at 790 K. The film thickness of the tungsten nitride linearly increased with
the increasing deposition time at 673 and 790 K without any orientation despite the film
thickness. The sticking probabilities, η, are 0.00044–0.00123 for Si(400) with different aspect
ratios under the conditions of 5–13 Pa and 10–20 min.
A Manipulation of Semiconducting GaN Nanowires by Dielectrophoresis Aligned Assembly Deposition (DAAD)
Authors: Lee Seung Yong , Kim Tae Hong , Suh Duk Il , Park Ji Eun , Suh Eun Kyung , Hong Chang Hee , Lee Sang Kwon
Published: March 2009

We report on investigation of the AC dielectrophoresis aligned assembly deposition
(DAAD) of gallium nitride nanowires (GaN NWs) with both the variation of the electric field and the
frequency. Our DAAD methods were used to align and manipulate GaN nanowires as well as to
extract the electrical properties of semiconducting nanowires. We observed that the ability of the
alignment strongly depends on the magnitude of the AC electric field and frequencies. For the higher
AC peak-to-peak electric fields (up to 20 Vp-p), the GaN nanowires have a better alignment across the
patterned Ti / Au electrodes with a high yield rate of ~ 90% over the entire arrays (in our case, 20
arrays) in the chip at the 20 kHz. From the transport measurements of our AC aligned GaN nanowires
using conventional three-probe schemes in field-effect transistor structures, we found that the
conductance of the GaN NWs increased for gating voltage greater than zero and decreased for gating
voltage less than zero, indicating these GaN nanowires have n-type dopants.
Impact of Acceptor Concentration on Electronic Properties of n+-GaN/p+-SiC Heterojunction for GaN/SiC Heterojunction Bipolar Transistor
Authors: Amari Koichi , Suda Jun , Kimoto Tsunenobu
Published: March 2009

The electrical properties of n+-GaN/p+-SiC heterojunction diodes have been investigated
by varying the acceptor concentration of p+-SiC epilayers (Na) and polytype of SiC (4H- and 6H-SiC).
The current-voltage (I-V) characteristics of diodes with Na ~ 1x1019 cm-3 were dominated by
tunneling-assisted current. The diodes with Na ~ 1x1018 cm-3 exhibit excellent characteristics and
6H-SiC may be a better choice from a view point of electron injection into p-SiC base. Compared to
previous investigations (Na<1016cm-3), we could obtain good rectification with p-SiC doped to
two-order-of-magnitude higher acceptor concentration.
In Situ Mass Spectrometry for Chemical Identification in SiC Epitaxial Deposition
Authors: Ponczak Brian H. , Oliver James D. , Cho Soon , Rubloff Gary W.
Published: March 2009

A quadrupole mass spectrometer unit was utilized to accurately detect the chemical
species present inside a SiC CVD reactor growth chamber before, during, and after epitaxial
deposition. The in-situ mass spectrometer has been able to confirm the presence of silane (SiH4)
and propane (C3H8) decomposition products (eg. Si and CH4) that were predicted from chemical
modelling, and give insight into specific reaction kinetics. Additionally, the mass spectrometer has
positively detected trace amounts of oxygen, which has helped to identify process weaknesses and
possible sources of vacuum leaks.
SiC Heteropolytype Structures Grown by Sublimation Epitaxy
Authors: Lebedev Alexander A.
Published: March 2009

In addition to possessing unique electrical properties, silicon carbide (SiC) can crystallize
in different modifications (polytypes). Having the same chemical nature, SiC polytypes may
significantly differ in their electrical parameters. In recent years, the world's interest in fabrication
and study of heteropolytype structures based on silicon carbide has considerably increased. This
paper considers studies concerned with fabrication of various types of heterostructures constituted
by different SiC polytypes by sublimation epitaxy, and their electrical parameters. It is shown that
heterostructures between SiC polytypes may have a better structural perfection than those
constituted by semiconductors that differ in chemical nature. A conclusion is made that SiC-based
heterostructures are promising for application in modern electronic devices.
Growth and Characterization of High-Quality 6H-SiC (0115) Bulk Crystals
Authors: Filip Octavian , Epelbaum Boris M. , Bickermann Matthias , Winnacker Albrecht
Published: March 2009

New results on bulk growth of 6H-SiC crystals along the [01-15] direction are presented.
The aim of our work is to improve the quality of the crystal grown by classical PVT method by
employing alternative growth directions, other than conventional [0001]. Using a specially designed
graphite crucible, crystals with an expansion angle of 30 degrees and diameters up to 40 mm have
been grown. No polycrystalline rim develops at the contact with the graphite wall. Concerning
specific defect content in the [01-15]-oriented crystals, they appear completely free of micropipes
and screw or threading edge ([0001]-oriented) dislocations. The [01-15] crystal relaxes adopting a
network of in-plane (0001) dislocations. They are not uniformly distributed reaching the maximum
density of about 106 cm-2.