bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Pulse Electric Current on Solidification Structures of Al-Si Alloys
Authors: Ban Chun Yan , Han Yi , Ba Qi Xian , Cui Jian Zhong
Published: March 2009

The effect of pulse electric current with different density on solidification structures of
hypoeutectic Al-7%Si, Al-10%Si and hypereutectic Al-22%Si alloys was studied. The shape and
distribution of α-Al and Si were analysed.The experimental results showed that α- Al of Al-7% Si
alloy is shortened when applied a pulse electric current during the solidification, and the
microstructure turns from the obvious columnar crystal into rosette. After treatment with pulse
electric current, the primary Si of Al-22%Si alloy was refined obviously. When the discharge voltage
was 3kV, Si tended to gather at the edge of the sample and the primary α- Al appeared in this
hypereutectic alloy. When the discharge voltage was 6kV, the primary Si was refined much more and
distributes uniformly. Pulse electric current treatment had no evident effect on the approximate
eutectic Al-10%Si alloy. The magnetic force was analysed under pulse electric current, and the reason
of the phenomenon was discussed
Correlation of Mechanical Properties with Defect Structure in Commercial Pure Al and Al-Mn Alloys Studied by Positron Annihilation Spectroscopy
Authors: Gomaa Ehsan. A.H. , Mohsen M. , Taha A.S. , Mostafa M.M.
Published: March 2009

The variations during isochronal annealing of cold-rolled commercial pure Al (1050) and
Al-Mn (3004) has been investigated between room temperature (RT) and 823 K. The annealing
stages have been identified as recovery, partial recrystallization, complete recrystallization and grain
growth using positron annihilation lifetime (PAL) spectroscopy, Doppler broadening of annihilation
radiation (DBAR) spectroscopy and Vickers microhardness (Hv) measurements. The retardation of
complete recovery in Al-Mn alloys is due to the presence of vacancy-Mn complexes. A positive
correlation has been found between positron annihilation parameters (τav & Snor) and mechanical
properties (Hv) for the two alloys under investigation.
Effect of Second Phases on Tensile Property in Artificial Ageing and RRA Process of Super-High Strength Aluminum Alloy
Authors: Ning Ai Lin , Liu Zhi Yi , Feng Chun , Zeng Su Min
Published: March 2009

The evolution of second phases and its effect on tensile mechanical property in artificial
ageing and RRA process of super-high strength aluminum alloy is investigated.The result of tensile
test shows that the samples of Al-Zn-Mg-Cu-Ag alloy aged at lower temperature(100°C) not only
have higher tensile strength up to 753Mpa but also relatively higher tensile elongation above 9% than
normal temperature(120°C) in artificial ageing. The sample of Al-Zn-Mg-Cu alloy has the highest
tension strength upto 788Mpa when aged at 100°C for 48 hours in single step of artificial ageing.
Further more in RRA process samples of Al-Zn-Mg-Cu alloy preaged at 100°C for 24 hours
retrogressed at 200°C for 7min and reaged at 100°Cfor 24 hours present the best tensile strength of
795Mpa than others. The tensile strength of Al-Zn-Mg-Cu alloy after RRA treated decreases with
prolonging of retrogression time and reageing time starting from 7mins and 24 houres respectively.
SEM observation shows that crack of the samples in tensile test is created at large particles in the
fracture while there are more particles of undissolved phase in Al-Zn-Mg-Cu alloy containing Ag.
TEM observation shows that the dominant strengthening particle corresponding to the peak strength
of Al-Zn-Mg-Cu alloy containing Ag when aged at 120°C for 8 hours is η’ phase while dominant
strengthening particle is G.P zone when aged at 100°C for 80 hours. However, η’ phase as the
dominant strengthening particles corresponds to the peak strength of Al-Zn-Mg-Cu alloy without
content of Ag when aged at 100°C for 48hours. TEM observation also shows that G.P zone as
strengthening particle is dominant in the samples of Al-Zn-Mg-Cu alloy reaged at 100°C for 24
hours, and strengthening particles is coarsened when the sample is retrogressed at 200°C and reaged
for a longer time. It is suggested that whether at the presence of coarse particles of undissolved phases
or when G.P zone and η’ particle grow up in the retrogression ,sample needs deformable G.P zone
instead of undeformable η’ in subsequent artificial ageing and reageing as dominant strengthening
particle, in order to present a larger freedom spacing for dislocation to slip and let the sample not to
behave too brittle to display high resistance to imposed plastic deformation or high tensile strength.
Alloying Behavior of Rare-Earth Er in Al-Cu-Mg-Ag Alloy
Authors: Li Yun Tao , Liu Zhi Yi , Liu Yan Bin , Dang Peng , Xia Qing Kun , Yu Ri Cheng
Published: March 2009

The alloying behavior of RE element of Er in Al-Cu-Mg-Ag alloys with addition of Er were
investigated in this paper. During solidification ,most of element Er segregated at grain boundaries in
the form of primary Al8Cu4Er phase and part of Er dissolved in the α-Al matrix. After rolling,
Al8Cu4Er phase could be fragmentated into dispersed particle which leaded to an increase of the
grain boundary strengthening . TEM observation and tensile strength test showed that small addition
of Er retarded the precipitation of Ω phase and prolonged the time corresponding to the peak
aging,with a remarkable increase of ductility.
Evolution of Flow Stress and Microstructure in an Al-Zn-MgSeries Alloy during Hot Deformation
Authors: Shen Jian , ShangGuan Yong Heng , Yan Xiao Dong
Published: March 2009

Evolution of flow stress and microstructures of an Al-Zn-Mg series alloy during
deformation at elevated temperatures and large ranges of strain rates have been investigated by
isothermal compression testing on Gleeble 1500 thermomechanical simulator. The results showed
that the flow stress exhibited a characteristic of peak stress followed by smoothing out in the imposed
strain rate and temperature ranges. The hot deformation of the alloy is a thermally activated process,
which is controlled by rate-controlling mechanisms of dislocation generation and dislocation
annihilation. The flow stress decreases with the increase of true strain at higher temperature and lower
strain rate, indicating that dynamic softening dominates instead of strain hardening during hot
deformation of the alloy. Microstructure observation revealed that typical subgrain cluster structures
obviously developed in the original elongated grains of the alloy during hot deformation. The
subgrain size of the alloy increased with deformation temperature and downturn of strain rate, where
the Zener-Hollomon parameter increased. Fine equiaxed recrystallized grains with large-angle grain
boundaries developed significantly in the alloy during hot compression at low Z values, implying
activation of dynamic recrystallization.
Effect of Extrusion Temperature and Rate on Formability and Microstructure of 7075 Aluminum Alloy
Authors: Wu X.K. , Zhang Xin Ming , Yuan G.C.
Published: March 2009

The effect of forward extrusion temperature and rate on the formability and microstructure
of 7075 aluminum alloy was investigated by means of scanning electron microscopy (SEM), optical
microscopy (OM) and hardometer. The results showed that the outflow rate was in the range of
6~2m/min with the extrusion temperature from 340°C to 420°C. Higher temperature resulted in lower
critical extrusion force, decreased permissible extrusion rate and obvious drop in the formability.
Lower temperature resulted in improvement in the formability but higher critical extrusion force,
which might lead to shuttingdown of the extruder. There were no obvious effects of extrusion
temperature and rate on the microstructure and hardness of the as-extruded alloy. It suggests that
dynamic recovery or partial recrystallization occurred in the alloy during extrusion.
Metallographic Characterization of Porosity in A Cast Aluminum Alloy A356-T6
Authors: Ran Guang , Zhou Jing En
Published: March 2009

Microporosity in both HIPped and non-HIPped unmodified aluminum cast alloy A356-T6
was quantified metallographically in terms of its area, area percentage, length, sphericity and
perimeter. In the studied materials, the secondary dendrite arm spacing (SDAS) values vary from
82μm to 96μm for both the HIPped and the non-HIPped castings. HIPping process significantly
reduces porosity area fraction and pore sizes. The maximum area fraction of porosity and maximum
pore area of the non-HIPped specimens are increased with increasing SDAS.
Effects of Stress on Structure Transformations in Metals
Authors: Hutchinson W. Bevis , Wynne Bradley P.
Published: March 2009

Possible effects of stress on the movement of grain boundaries and phase boundaries are considered
in terms of available driving forces and mechanisms. Examples of some of these effects are
presented from the literature and new experimental results. Stress may influence the kinetics of
transformation and also the microstructure and texture of the product material.
An Analysis of Deformation Microstructure and Subsequent Recrystallisation in Hot Deformed Aluminium Alloy AA5052 Using Forward and Reverse Torsion
Authors: Lopez-Pedrosa M. , Wynne Bradley P. , Rainforth Mark W.
Published: March 2009

The effects of strain path reversal on the microstructure in AA5052 have been studied using high resolution EBSD. Deformation was carried out using two equal steps of forward/forward (F/F) or forward/reverse (F/R) torsion at a temperature of 300°C and strain rate of 1s-1 to a total strain of 0.5. In both cases the deformation microstructure in the majority of grains analysed consisted of microband arrays clustering at specific angles to the macroscopic deformation axes. For the F/F condition microbands clustered around -20° and +45° to the maximum principle stress direction, whilst for the F/R condition significantly more spread in microband angle was observed. This suggests that the microbands formed in the forward deformation have or are dissolving and any new microbands formed are related to the deformation conditions of the final strain path. This leads to the conclusion that instantaneous deformation mode determines the orientation of new microbands formed whilst a non-linear strain path history influences the range of misorientation angle in the material through the dissociation of previously formed microbands and the formation of new microbands at the new straining condition, leading to a lower level of misorientation angle. Analysis of material subjected to static annealing at 400°C for 1 hour appears to correspond with these observations as the F/F material was completely recrystallised with a fine grain structure whilst the F/R material had no major signs of recrystallisation.
Uniaxial and Plane Strain Compression Behaviour of Magnesium Alloy AZ31: A Comparative Study
Authors: Al-Samman Talal , Ahmad Bashir , Gottstein Günter
Published: March 2009

Texture evolution and microstructure development of hot extruded magnesium alloy
AZ31 deformed by PSC and uniaxial deformation at select temperatures and a constant strain rate
of 10-4 s-1 were investigated and compared using X-ray techniques, electron back scattered
diffraction (EBSD) and optical microscopy. At a deformation temperature of 200 °C both
deformation routes resulted in a similar crystallographic texture and showed a heterogeneous
microstructure consisting of highly deformed zones appearing as huge and/or elongated grains
containing twins and shear bands embedded in a very fine-grained microstructure. High temperature
deformation (400 °C) gave rise to completely different deformation textures for the two processes.
Uniaxial deformation tended to randomize the initial extrusion texture, whereas in PSC a prismtexture
{10-10}<11-20> prevailed. The flow stress was found to be strongly dependent on loading
conditions and deformation modes.
Simulation of Rolling and Recrystallization Textures in Aluminium Alloy Sheets
Authors: Engler Olaf
Published: March 2009

Computer-based alloy and process development requires integration of models for simulating the evolution of microstructure, microchemistry and crystallographic texture into process models of the thermo-mechanical production of Al sheet. The present paper focuses on recent developments in linking softening modules that simulate the progress of recovery and recrystallization with the following texture changes to deformation and microchemistry models. The potential of such coupled simulations is illustrated by way of the thermo-mechanical processing of Al-Mn-Mg AA 3104 can stock. In particular, the impact of inter-stand recrystallization between the tandem hot rolling passes as well as recrystallization during coil cooling (“self-annealing”) on the resulting hot strip and final gauge textures are explored. Finally, the predicted textures are input into a polycrystal-plasticity approach to simulate anisotropic properties (earing behaviour) of the sheets. Thus, it is possible to link the materials properties at final gauge to the decisive steps of deformation and recrystallization along the thermo-mechanical process chain.
Effect of Deformation Route on Recrystallization Behaviour of 1100 Aluminum Sheet
Authors: Sakai Tetsuo , Mori Kohki , Utsunomiya Hiroshi
Published: March 2009

It is believed that the shear deformation superimposed on rolling deformation accelerates
grain refinement. However, it has not yet been completely understood whether the grain refinement is
due to the increase in amount of equivalent strain, or the change in strain path. In the present study,
three different strain paths in plane strain - (1) simple shear, (2) compression and (3) the combination
of simple shear and compression - are introduced into 1100 aluminum sheet. The recrystallization
behaviours are compared. Plane-strain compression was achieved by a normal rolling, while the
simple shear was achieved by a continuous ECAE (conshearing). The combined strain path was
achieved by the conshearing subsequently followed by the rolling. The same amount of the equivalent
strain of 1.28 was accumulated in the three paths. The ratio of shear strain to compressive strain was
varied by three levels in the combined strain process. After heat treatment, the material processed by
the combined strain path gave a finer recrystallized grain size than both of the monotonic strain paths
at either annealing temperature. The finest recrystallized grain size was obtained at the shear strain
ratio of 0.6 to the total equivalent strain. It was found that the change in strain path was effective for
introducing more new high-angle grain boundaries.
Ferrite Formation during Slow Continuous Cooling in Steel
Authors: Offerman S. Eric , Strandlund Henrik , van Dijk Niels H. , Sietsma Jilt , Lauridsen Erik M. , Margulies L. , Poulsen Henning Friis , Ågren John , van der Zwaag Sybrand
Published: March 2009

Ferrite formation during austenite decomposition in carbon-manganese steel is studied during slow continuous cooling by three-dimensional x-ray diffraction microscopy at a synchrotron source. The ferrite fraction and nucleation rate are measured simultaneously and independently in real time in the bulk of the specimen. Thermodynamic calculations involving both ortho- and paraequilibrium have been performed to determine the driving force for nucleation. From the experiments and thermodynamic calculations the activation energies are estimated for nucleation and the transfer of iron atoms across the interface of the cluster during ferrite nucleation in steel.
Texture Evolution of Tertiary Oxide Scale during Steel Plate Finishing Hot Rolling Simulation Tests
Authors: Suarez Lucia , Petrov Roumen H. , Kestens Leo , Lamberigts M. , Houbaert Yvan
Published: March 2009

Thin tertiary scale layers have been grown on ULC steel specimens under controlled
conditions. After heating under a protective atmosphere (nitrogen), the samples have been oxidised
in air for various oxidation times at 1050°C. These experiments are considered a quantitatively and
qualitatively reasonable simulation of the scale formation and growth occurring before hot rolling.
Immediately after controlled oxidation, some of the samples were subjected to plane strain
compression, in order to simulate the finishing hot rolling process. This approach provided a better
insight into the deformation behaviour of the tertiary oxide layer in the first hot rolling pass.
The layers produced were examined under the SEM using the EBSD technique for texture
characterisation and phase morphology determination. The texture of the deformed oxide scales,
originally grown on ULC steel at 1050°C, was determined in order to achieve a better understanding
of their complex deformation behaviour. This paper gives a first approach of the study of deformed
oxides by EBSD. Strongly textured wustite grains with a clearly pronounced columnar structure
were observed after oxidation at 1050°C. As the substrate deformation probably affects the oxide
layer, orientation relationships between scale layer and substrate were observed. The detailed EBSD
study reveals that the oxide layer can accommodate a significant amount of deformation. The oxide
layers exhibit good adhesion to the substrate and remain homogeneous over the thickness after
compression.
On the Phenomenology and Mechanics of Super Plastic Flow in Advanced Structural Materials
Authors: Muñoz-Andrade Juan Daniel
Published: March 2009

In connection with ancient and recent view on cosmology, it is interesting to note that our
universe could be a spherical crystal and it moves as a crystal in a relative position with others
spherical universes, where the Burgers vector for cellular dislocations dynamics is the Hubble length:
λH=1.32x1026m. The expansion process of this polycrystalline spatially extended system obey the
hyperbolic granular flow, which it is due to an accelerated motion manifested during the deformation
process of super plastic advanced structural universes in a similar behaviour of super plastic advanced
structural materials. Consequently, in this work the phenomenology and mechanics of super plastic
flow are analyzed in the context of the unified interpretation of Hubble flow, plastic flow and super
plastic flow, where the combination of fundamentals constants with the natural Planck length, allows
obtain in a closed agreement with the Orowan equation the magnitude of the nature Burgers vector of
dislocation in the cosmic structure for the universe as follow:
1.62 10 . 35
3
0 x m
c
H G
b
P
−
⊥ ⊥
⊥ = = = =
h
λ
ρ ν
Where, b⊥ = magnitude of the nature Burgers vector for the universe (b⊥ = 1.62x10-35m), λP = Planck
length (λP = 1.62x10-35m), H0 = the Hubble parameter (H0=70 (km/sec)/Mpc = 2.26854593 x10-18s-1),
ρ⊥ = dislocation density (ρ⊥ = 1.273x1011 dislocations/m2) in the universe. ν⊥ = the recession
velocity of galaxies related with dislocations dynamics in the cosmic structure (ν⊥ = 1100x103 m/s, it
is the recession velocity of the Virgo super cluster at 16 Mpc distance). h = h / 2π . Here h = the
Planck constant (h = 6.6262x10-34 Joule-s), G = the Newtonian constant (G = 6.67259x10-11 m3/kg s2)
and c = the speed of light (c = 299 792 458 m/s) [1-3].
Production of Ti-6Al-4V Sheets for Low Temperature Superplastic Forming
Authors: Salishchev Gennady A. , Valiakhmetov Oleg R. , Beck Werner , Froes F.H.
Published: March 2009

The availability to produce Ti-6Al-4V sheet material with submicron-grained
microstructure for superplastic forming (SPF) has been studied. The laboratory scale sheets with an
average grain size of 0.3 μm and the commercial size sheets with an average grain size of 0.65 μm
were produced by pack rolling manufacturing technique from the forgings with pre-formed
submicrocrystalline (SMC) structure. The sheets possessing isotropic mechanical properties in the
sheet plane had higher yield strength, ultimate tensile strength. Over the exceptionally low
temperature range of 700-750°C the SMC sheets demonstrated enhanced superplastic properties,
namely an initial flow stress of 20-25 MPa and elongation more than 600% at the strain rate of
3×10-4/s. The sheet material with SMC structure was characterized by well formability compared to a
conventional sheet under low temperature superplastic conditions.
Analysis of the Behavior of a Clad Material Al-Zinag-Al
Authors: Casolco S.R. , Negrete-Sánchez J. , López Parra M. , Torres-Villaseñor Gabriel
Published: March 2009

In the present work, we studied the nanostructural behavior of a denominated alloy Clad-
Zinag, which is composed of a single layer of Zinag coated on both surfaces by an aluminum film. The
alloy was then deformed by two different processes, one in which a superplastic conformed technique
was applied and the second was by way of tensile testing. For both techniques, the alloy was examined
and analyzed by viewing the materials topography with an atomic force microscope (AFM). From
these techniques we were able to observe both processes of plastic deformation and the presence of
marks which correspond to bands of grain sliding. This mechanism is a result of superplastic
deformation, and influences the grain size of aluminum. Nevertheless, we must clarify that the name
of mesoscopic band of slides, is based on a study according to Vinogradov.
The Research on Superplasticity of Two New Ti Alloys
Authors: Zhao Yong Qing , Qu Heng Lei , Zeng L.Y.
Published: March 2009

The superplastic tensile deformation behavior and structural evolution of two kinds of α+β
titanium alloys were investigated in this paper, one is a new high strength high toughness Ti alloy with
damage tolerance called TC21, and the other is a new superplastic Ti alloy so called Ti-SP2500. The
results indicated that TC21 alloy has good superplasticity at the temperature from 720 to 960 and
with the strain rate of 5.510-5s-1∼1.110-2s-1. On the optimal superplastic condition, the maximum
elongation is over 1300%. During the superplastic tensile deformation, the dynamic recrystallization
occurs in deformation zone of the specimens and the superplasticity is improved. Ti-SP2500 alloy has
good superplasticity at the temperature from 720°C to 800°C and with the strain rate of 6.67
10-4s-1∼1.1110-2s-1. The maximum elongation for Ti-SP2500 alloy will exceed 2200% at 780°C with
the strain rate of 5.5610-3s-1. Its superplastic deformation mechanism is controlled by grain boundary
sliding, and the grain deformation and dislocation creep has the coordinating action.
Superplastic Forming and Thickness Distribution of Ti6Al4V Alloy Denture Base
Authors: Jiang S.S. , Zhang Kai Feng
Published: March 2009

In this paper, the process is divided into two steps. (1) First, the ceramic die used to
fabricate the denture base was made by mixing the green of ZrO2 and TiO2 with PVA and press them
into the oral cavity model to get the ceramic die before sintered. Then it was sintered to be the ceramic
die after sintered in the atmosphere. (2) Second, the 0.8mm Ti-6Al-4V plate covered with BN was
fabricated to be denture base by blow forming at the optimal superplastic forming temperature using
nitrogen gas. The pattern of the Ti6Al4V denture base was the same as the detail of the ceramic die.(3)
Third, the thickness of Ti-6Al-4V alloy denture base was investigated and the accuracy was measured
by compared the distance between the marked points of the framework against the ceramic die.
Although the thickness of denture base was reduced by superplastic forming, the framework had
about 78.5% of the original plate thickness. Differences in the thickness did not significantly affect
the gap discrepancy and the accuracy of fit of the denture base would satisfy ordinary clinical
requirements.
Superplastic Micro Deep Drawing of Fine-Grained Nickel at Elevated Temperatures
Authors: Ding S. , Zhang Kai Feng , Wang Guo Feng
Published: March 2009

Superplastic deformation behavior of nanocrystalline nickel was investigated under
equibiaxial tension at different strain rates and forming temperatures. The nickel sheets with a
thickness of 0.1 mm were prepared by pulse electrodeposition process. The average grain size of the
as-deposited nickel was 70 nm and equiaxed. To determine the optimum processing parameters
relevant to micro deep drawing, uniaxial tensile tests were carried out at temperatures ranging from
370°C to 500°C and strain rates ranging from 10-4 to 10-3s-1. In the selected temperature and strain
rate ranges, the elongation value is larger than 200%, which indicates good superplastic formability of
the electrodeposited nickel. Equibiaxial forming was subsequently performed at 370°C and 450°C,
using a punch with a diameter of 1mm. The effects of forming temperature, punch rates on deep
drawing process were experimentally investigated. The results indicated that the nickel specimens can
be readily drawn at 450°C and punch rates ranging from 0.1mm• min-1 to 5mm• min-1. TEM and
SEM were also used to examine microstructures of the as-deposited nickel sheet and deformed nickel
specimens. The observations showed that significant grain growth occurs even at low superplastic
forming temperatures. Microstructure was found to depend on the stress state and level of
deformation.
Deformation Behavior of Zr-Based Metallic Glass and Microforming of Microgears
Authors: Guo X.L. , Shan De Bin , Guo Bin , Wang C.J. , Zhou J. , Xu Z.H.
Published: March 2009

The deformation behavior of the Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass
(Vit1) in the supercooled liquid region was investigated. The stress-strain relations for Vit1 at the
different specimen sizes were established in a uniaxial compression test using the microforming
system. Furthermore, the effects of forming time, temperature and punch velocity on the flow stress of
the specimen with a typical size of Φ1×1.5 mm were analyzed. The results indicate that Vit1 has
excellent superplastic microformability at minimum forming time, higher temperature and lower
punch velocity. Based on the research, Vit1 microgears with reference diameter of Φ1 mm and
modulus of 0.1 mm were manufactured using the closed die forging. Optimum processing parameters
were obtained. In order to evaluate the quality of Vit1 microgears, scanning electron microscope,
atomic force microscope and nanoindentation tests were applied. It is found that the parts with good
qualities can be formed successfully in the supercooled liquid region.
Low Temperature Superplasticity and Intragranular Misorientation in Severely Rolled Sheets of Al-4.5%Mg-0.7%Mn Based Alloys
Authors: Takayama Yoshimasa , Ochiai H. , Furushiro Norio , Kato Hajime , Watanabe Hideo
Published: March 2009

Severely rolled sheets of Al-4.5%Mg-0.7%Mn based alloys have been prepared to achieve
grain refinement leading to low temperature superplasticity. Rolling is one of straining technique
which has a high possibility of industrial application. The alloys used were T1: base one adding
0.08%Zr and 0.05Ti for suppression of grain growth, F1: 0.80%Fe addition and F2: 1.92%Fe addition
to increase nucleation sites of recrystallization. For comparison, M1: Al-4.2%Mg was also prepared.
All of samples were 99.8% cold rolled to thin sheet 0.1mm thick. The maximum elongation of 150%,
which was markedly large in consideration of specimen thickness of 0.1mm, was obtained at 533K
and 1.4×10-3s-1 for T1 sample while the elongations for F1 and F2 showed less than 100%. On the
other hand, M1 exhibited larger elongation of 190% at 533K and 1.4×10-3s-1. Further, difference in
superplastic deformation of these alloys was investigated by using SEM/ EBSP analysis of
intragranular misorientation, which reflects strain or stored energy generated during deformation with
dislocation glide, to discuss the deformation mechanism.
Study of the Superplasticity of Copper Alloys Used for Solid Cages
Authors: Chen F.X. , Li He Jun , Guo J.Q. , Yang Yong Shun , Xu G.Z.
Published: March 2009

The superplasticity of cast copper alloys used for solid cages is studied by tests of tension
and compression in this paper. The results show that cast copper alloys exhibited superplasticity
without any pretreatment. Cast aluminum bronze is of superplasticity at the temperatures between
750~800°C with the initial strain rate 1×10-2s-1, the elongation being over 260%. Under the condition
of superplasticity compression with the strain rate (1.136~9.091)x10-4s-1 at temperatures between
600~650°C, the cast lead brass presents the superplasticity effect with the maximum flow stress under
2MPa.
A New Inorganic Membrane: TiO2 Ultrafilter Based on Functionally Graded Porous Alumina
Authors: Falamaki Cavus , Veysizadeh Jamileh
Published: March 2009

The fabrication of thin nanoporous TiO2 layers (thickness < 2 μm) on functionally graded
porous alumina (thickness = 2 mm) is reported for the first time. The membrane is produced by dip
coating TiO2 sols on the alumina support. The alumina porous support is produced using centrifugal
casting with an acceleration of 3000g .The average pore size of the support is ca. 0.5 μm while its
upper surface on which the membrane layer is deposited has an average pore diameter of 0.38 μm
and average porosity of 10.7 %. The sol is produced by the peptization technique using
tetrapropylorthotitanate as precursor. For the first time, a synthesis procedure has been implemented
which allows the production of TiO2 sols with average particle sizes from12 to 22 nm. Using the
BET technique, the average pore size and meso-porosity of the unsupported sintered TiO2
membranes as a function of sintering temperature and ZrO2 impurity concentration (0.0, 0.2, 0.6
and 1.0 wt. % of ZrO2) have been determined. The kinetics of the membrane layer anatase to rutile
transformation reaction has been investigated as a function of ZrO2 impurity concentration
introduced to the TiO2 sol during its preparation. The lack of macrocraks in the ultrafilter layer of
the sintered composite was confirmed using the gas permeability and SEM techniques. The main
outcome of this work is that the support has an outstanding low surface roughness (< 0.4 μm)
allowing deposition of a defect free single layer of TiO2 in one step
Characterization of Al/SiC Nanocomposite Prepared by Mechanical Alloying Method
Authors: Shokuhfar Ali , Dashtbayazi M.R. , Alinejad M.R. , Shokuhfar Tolou
Published: March 2009

In this research work, a high-energy ball mill has been applied to prepare an Al/SiC nanocomposite. The formation mechanism of the nanocomposite was investigated. This nanocomposite contained the nanocrystalline characteristics. Crystallite size, lattice strain and particle size of the nanocomposite as a function of milling time were determined. SEM micrographs showed that the nanocomposite powders agglomerated after milling. The particle size analysis confirmed the agglomeration of the nanocomposite particles. TEM observations showed that the SiC particles were in the nanometer size and these particles embedded in the Al matrix, and the nanocomposite produced in the final stage of mechanical alloying. In addition, a simple model checked for the refinement of the crystallite and the particle size of nanocomposite.
Fracture Toughness and Crack Deflection in Porous Multilayered Ceramics: Application to NiO-YSZ
Authors: Joulaee N. , Makradi Ahmed , Ahzi Saïd , Khaleel Moe A.
Published: March 2009

The arrangement of ceramic layers in laminated structures is an interesting way to enhance the flaw tolerance of brittle ceramic materials. The interfaces are expected to deflect cracks, increasing the fracture energy of the laminate compared to a monolithic material and thus raising the toughness. The target of this study is to predict the volume fraction of pores, in porous layers, required to cause crack deflection. Formulation of the fracture toughness and fracture energy as function of the material porosity is presented for random and ordered pores distribution. The effect of crack tip-flaws interaction is considered to estimate the pores volume fraction needed for crack deflection. In this work, dense and porous layers of NiO-YSZ material similar to the one used in the fuel cells technology are considered. The fracture energy of a porous material with an ordered distribution of pores shows a possibility of crack deflection at a porosity of 22.5%. However for a system with randomly distributed pores this possibility can be seen at 36% of porosity.
Oxynitride Glasses: Preparation, Properties and Implications for Mechanical Behaviour of Silicon Nitride
Authors: Hampshire Stuart , Pomeroy Michael J.
Published: March 2009

Oxynitride glasses are found at grain boundaries, i.e. triple point junctions and intergranular films, in silicon nitride based materials as a result of cooling of liquid phases formed by reaction of sintering additives with silicon nitride and silica present on the nitride surface during the densification of the ceramics. The glass chemistry, particularly the content of modifying cation, usually Y or a rare earth (RE) ion, and the volume fractions of these oxynitride glass phases within the ceramic affect the properties of silicon nitride such as fracture toughness and creep at high temperature. As nitrogen substitutes for oxygen in silicate and alumino-silicate glasses, increases are observed in glass transition and softening temperatures, viscosities (by two to three orders of magnitude), elastic moduli and microhardness. If changes are made to the RE:Si:Al ratios or as the size of the rare earth cation decreases, properties such as viscosity can be increased by a further two to three orders of magnitude. These effects have a strong impact on the mechanical properties of silicon nitride based ceramics, especially creep resistance. This paper provides an overview of previous work on oxynitride glasses and outlines the effect of glass composition on their properties and discusses the implications for high temperature behaviour of Si3N4 ceramics.
Effect of Cooling Rate on Glass Formation for Some Oxynitride Glasses
Authors: Redington Wynette , Redington Murt , Hampshire Stuart
Published: March 2009

Rapid cooling rates and quenching have traditionally been associated with glass formation. Hampshire et al. [1] investigated oxynitride glasses cooled in a tungsten resistance furnace at approximately 200oC/min and found that fast cooling rates were only important near the limits of the glass-forming region. In the current work on various M-Si-Al-O-N (M=Y, La, Yb, Nd) systems, it was found that even at a relatively slow cooling rate glass formation was still possible for a wide range of compositions. Different cooling rates were investigated to determine the minimum cooling rate at which a glass will form. Quantitative X-ray analysis of melted compositions indicated the relative amounts of amorphous phase and crystalline phase.
Computer Simulations Combining Finite Difference and Finite Element Methods: Solute Drag on Migrating Grain Boundaries in Three-Dimension
Authors: Gao M.C. , Gruber Jason , Rollett Anthony D. , Kuprat Andrew P.
Published: March 2009

The current study aims to improve our fundamental understanding of solute segregation and solute drag on migrating grain boundaries (GB) in three dimensions. Computer simulation combines finite difference and finite element methods. An exemplary case study is reported, in which a spherical grain is embedded inside a cubic grain and shrinks as a result of motion by curvature, as a preliminary to modeling grain growth in single phase materials. The results agree qualitatively with literature studies in 1-D.
Recrystallization of Ferric Oxyhydroxides Consisting of FeO6 Octahedral Units via Aqueous Solution
Authors: Inoue Katsuya , Kwon Sang Koo , Shinoda Kozo , Suzuki Shigeru , Waseda Yoshio
Published: March 2009

Solid particles of ferric oxyhydroxides or iron oxide were recrystallized from ferrous and ferric ions dissolved in aqueous solution. There are different structures of α-FeOOH, β-FeOOH and γ-FeOOH in the ferric oxyhydroxides, of which the formation is influenced by reaction conditions such as oxidation rate of ferrous ions. In this work, a few factors affecting the formation of the ferric oxyhydroxides and iron oxides, which was converted from hydrosulfate green rust, has been studied using different methods. The hydrosulfate green rust (GR2) was synthesized from solutions of ferric sulfate (Fe2(SO4)3), ferrous sulfate (FeSO4), and sodium hydroxide (NaOH), and they were oxidized by gas containing oxygen. X-ray diffraction measurements and X-ray absorption spectroscopy were used for analyzing the structure and chemical state of solid particles extracted from the suspension during the oxidation. The morphology of the particles was observed by transmission electron microscopy. The results showed that γ-FeOOH or Fe3O4 particles were formed together with α-FeOOH particles during conversion from the green rust, depending on oxidation temperature, oxygen flow rate and addition of manganese. This indicates that the species of ferric oxyhydroxides or iron oxides formed in aqueous solution is sensitively influenced by reaction conditions.
Simulation of Primary Recrystallization in Automotive Steels by Consideration of Particle Pinning
Authors: Choi Shi Hoon , Kim B.J. , Kim S.I. , Choi Jin Won , Chin Kwang Geun
Published: March 2009

A modified two dimensional (2-D) Monte Carlo (MC) technique was used to simulate primary recrystallization in automotive steels containing fine particles. In order to consider anisotropic properties of grain boundary energy and grain boundary mobility, functions of boundary misorientation were introduced. Orientation-dependent stored energy developed in 80% cold-rolled interstitial free (IF) sheet steel was evaluated by reconstructing of data measured using electron back-scattered diffraction (EBSD) analysis. A subgrain method based on subgrain structure is used for quantitative analysis of the stored energy. The simulation reveals that particles affect evolution of microstructure during recrystallization. The simulation provided a theoretical foundation for understanding effect of particles on the final microstructures and crystallographic textures.
Nanostructured Aluminium - Recovery and Recrystallization
Authors: Hansen Niels , Huang X. , Godfrey Andrew
Published: March 2009

The isochronal annealing behavior of nanostructured commercial purity aluminium (AA1100 and AA1200) following either cold – rolling or accumulative roll bonding up to an ultra high strain of εvM = 6.2 (99.5% reduction in thickness) has been studied via hardness testing and by a microstructural investigation. A large effect of rolling strain is observed on the recovery at temperatures below approx. 200 °C. At higher temperatures an assessment of the changes in hardness and microstructure leads to a characterization of the annealing process as one of conventional (discontinuous) recrystallization.
Anomalous Rolling and Annealing Textures of Cold Rolled Copper Foils
Authors: Kim Su Hyeon , Han Seung Zeon , Kim Chang Joo , Ok Soon Young , Hwang In Youb , Yin Fu Xing
Published: March 2009

Copper foils cold rolled up to 92% reduction exhibited a low intensity of the β-fiber texture and a high intensity of the cube and RD (rolling direction)-rotated cube components. After annealing, the recrystallization texture of the foils could be characterized by the mixture of the cube and the S components. An initial strong cube texture with a large grain size might remain a less developed rolling texture component, cube or RD-rotated cube, which would be the source of the S component in the recrystallization texture.
Dynamic Recrystallization Mechanisms on Spot Welding of 6008 Aluminium Alloy to Steel by Friction Stir Welding
Authors: Bozzi Sandrine , Etter Anne Laure , Baudin Thierry , Robineau A. , Goussain Jean Claude
Published: March 2009

At the prospect of a lightening of the automobile structures, welded spots have been
realized on a stacking of two sheets (a 6008 aluminium alloy on steel) by Friction Stir Welding
(FSW). Different process parameters have been tested but only the influence of the dwell time will
be described in the present paper. The dwell time corresponds to the time during which the probe
stays in rotation at its bottom location before extracting.
A study of the microstructures and the crystallographic textures associated to mechanical tests
(shear and tensile tests) allowed to determine the best set of welding parameters. The recrystallized
area around the welding spot has been characterized by Electron BackScattered Diffraction
(EBSD). The aim of the present work is to identify the recrystallization mechanisms which occur
during welding, and to understand the influence of the dwell time on the recrystallized area.
A mechanism of continuous dynamic recrystallization has been identified since misorientation of
sub-boundary increases close to the weld and this for all the dwell times tested. Elsewhere, it has
been found that the increase of the dwell time induces a larger recrystallized zone.
Microstructural Evolution Deformed Heavily by High Strain Rate at High Temperature Range in Ultra Low Carbon Steel
Authors: Kang Joo Hee , Torizuka Shiro , Hanamura Toshihiro
Published: March 2009

The microstructural change was observed during large strain high Z deformation with high strain rate in high temperature range using ultra low carbon steel. The finer grains were obtained as decreasing the deformation temperature and increasing the strain rate. And the fraction of high angle grain boundaries became higher in low deformation temperature and strong texture of ferrite recrystallized dynamically was measured such as ND//<100>,<111> and RD//<110>. The change of grain size could be analyzed by Zener-Hollomon parameter, whereas the duration has large effect on the deviation of expected grain size in deformation with high strain rate.
Three Dimensional Characterization of Grain Structures by EBSP and 3DXRD
Authors: Hannesson Kristofer , Juul Jensen Dorte
Published: March 2009

Grain structures in polycrystalline materials are typically three dimensional (3D)
structures, but by far the most characterizations of grain structures are done by microscopy and are
thus limited to 2D. In the present work 3D grain structures in a well-annealed cylindrical
aluminium (AA1050) sample is characterized and analyzed. The characterization is done by 2
methods
i) by non-destructive 3-dimensional x-ray diffraction (3DXRD)
ii) by serial sectioning and subsequent EBSP mapping of entire circular 2D sample sections;
50 sections are mapped
In total 333 grains are reconstructed. It is found that the 3D grain morphologies can be quite
complex in particular for the larger grains, the number of neighbours varies significantly and values
above 20 are not unusual. When the results from the 2 methods are compared, it is found that the
crystallographic agreement is very good and within experimental uncertainties. Slightly more
significant differences are found when the reconstructed grain morphologies are compared. Reasons
for this are discussed.
Grain Boundary Atomic Structures in SrTiO3 and BaTiO3
Authors: Yamamoto Takahisa , Mizoguchi Teruyasu , Choi S.Y. , Sato Yukio , Shibata Naoya , Ikuhara Yuichi
Published: March 2009

SrTiO3 bicrystals with various types of grain boundaries were prepared by joining two single crystals at high temperature. By using the bicrystals, we examined their current-voltage characteristics across single grain boundaries from a viewpoint of point defect segregation in the vicinity of the grain boundaries. Current-voltage property in SrTiO3 bicrystals was confirmed to show a cooling rate dependency from annealing temperature, indicating that cation vacancies accumulate due to grain boundary oxidation. The theoretical results obtained by ab-initio calculation clearly showed that the formation energy of Sr vacancies is the lowest comparing with Ti and O vacancies in oxidized atomosphere. The formation of a double Schottky barrier (DSB) in n-type SrTiO3 is considered to be closely related to the accumulation of the charged Sr vacancies. Meanwhile, by using three types of low angle boundaries, the excess charges related to one grain boundary dislocation par unit length was estimated. In this study, we summarized our results obtained in our group.
Three-Dimensional Microstructure Reconstruction Using FIB-OIM
Authors: Lee Suk Bin , Rollett Anthony D. , Rohrer Gregory S.
Published: March 2009

A new method for reconstructing a three-dimensional microstructure using the focused ion beam-orientation imaging microscopy (FIB-OIM) is introduced. The technique is important for the study of three-dimensional microstructures of materials because it can automatically align (register) a series of parallel sections with both topological information and orientation information at the sub-micrometer scale. Using voxel-based tessellation, a three-dimensional microstructure is reconstructed by registering each section. The application of the method to a cubic material is described and, based on the reconstruction, the grain shape and grain size distribution are characterized.
Role of Grain Boundary Segregation in Austenite Decomposition of Low-Alloyed Steel
Authors: Suzuki Shigeru , Tanino M.
Published: March 2009

The influence of addition of small amounts of boron and nitrogen on the microstructure formed by austenite decomposition in low-alloyed manganese steels was investigated. In order to understand microstructural changes by addition of boron and nitrogen, Auger electron spectroscopy was used for analyzing prior austenite grain boundaries in steels doped with phosphorus, boron and nitrogen. The results by microstructure observation showed that the formation of Widmanstätten ferrite was suppressed by addition of a small amount of boron in the steels, whereas Widmanstätten ferrite appears to be formed again by addition of boron and nitrogen. The Auger spectra showed that small particles of boron nitride were detected on grain boundaries in steel doped with boron and nitrogen, while boron was segregated at grain boundaries in steel with boron. This indicates that segregation of boron at grain boundaries and/or sub-boundaries may suppress the formation of Widmanstätten ferrite, while the formation of boron nitride seems to be ineffective to suppression of the formation of Widmanstätten ferrite in steels doped with boron and nitrogen.
Degradation of Al/SiCp Composites Processed with Fly Ash via Reactive Infiltration
Authors: Escalera-Lozano Rodrigo , Gutiérrez-Chavarría Carlos A. , Pech-Canul Max A. , Pech-Canul Martin I.
Published: March 2009

The degradation in ambient atmosphere of Al/SiCp composites prepared by the reactive infiltration of SiCp preforms containing fly ash has been investigated. SiCp/fly-ash preforms in the form of plates (3 cm x 4 cm x 0.5 cm) with 50 % porosity are infiltrated by an Al- 8 Si-15 Mg (wt. %) alloy under argon atmosphere at 1050, 1100 and 1150 °C, for 50, 60 and 70 min. Characterization by XRD, SEM and EDX of composite specimens shortly after processing do not reveal the presence of the unwanted Al4C3 phase. However, in addition to Al, Si and SiC, MgAl2O4 and Mg2Si phases are detected. One month after the infiltration trials, white and gray powders are present on the composite specimens, accompanied by pitting corrosion and cracks which propagate with time. Although analysis by XRD of the degradation products reveals only Al4C3 in addition to the above mentioned phases, results from SEM, IR absorption and ICP also suggest the presence of Al(OH)3 and Mg(OH)2, probably from the interaction of Al4C3 and Mg2Si with water. It is considered that Mg2Si in the powders acts as an anode in a galvanic couple with atmospheric moisture as the electrolyte. The crack pathway through SiC, intermetallic AlFeMnSi and Si rich zones implies that one or more of these phases worked as the cathode. In summary, degradation of the composites is explained by the combined effect of galvanic corrosion caused by second phases and the interaction of Al4C3 with atmospheric moisture.