bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulation and Experimental Research on Superplasticity of Ceramic/Ceramic Laminated Composite
Authors: Wang Guo Feng , Wu D.Z. , Wang C.W. , Han Wen Bo
Published: March 2009

In order to investigate the superplasticity of ceramic/ceramic laminated composite under
tensile stress, the superplastic deep-drawing process was simulated by FEM. The results shown that,
the strain and stress conditions of laminated composite, made by ceramic with different superplastic
formability, are better than that of monolithic ceramic. Consequently, the material may exhibit high
superplasticity. To testify this, some experiments were carried out. Tape casting and hot-press
sintering are used to fabricate Al2O3/3Y-TZP laminated composite. As-received material is
deep-drawing at high temperature to research its superplasticity. The results shown that, when
suitable strain rate and forming temperature were used, the as-received material has excellent
superplasticity.
Homogeneous Flow of In Situ Bulk Metallic Glass Matrix Composite
Authors: Chan K.C. , Chen Q. , Liu L.
Published: March 2009

The compressive deformation behavior of as-cast Zr55.9Cu18.6Ta8Al7.5Ni10 Bulk Metallic
Glass (BMG) composite with micro-scale particles of Ta-rich solid solution embedded in an
amorphous matrix was investigated in the supercooled liquid region. It was found that the apparent
viscosity of the BMG is dependent on temperature and strain rate. A deviation from a Newtonian
behavior was observed at high strain rate and low temperature. The experimental results can be
described by a master curve based on a stretched exponential function and the free volume theory. The
structural state and the thermal ability of the BMG composite after deformation are also discussed in
the paper.
Cavitation Behavior of Ultra-Fine Grained Ti-6Al-4V Alloy Produced by Equal-Channel Angular Pressing
Authors: Ko Young Gun , Kwon Yong Nam , Lee Jung Hwan , Shin Dong Hyuk , Lee Chong Soo
Published: March 2009

Cavitation behavior during superplastic flow of ultra-fine grained (UFG) Ti-6Al-4V alloy
was established with the variation of grain size and misorientation. After imposing an effective
strainup to 8 via equal-channel angular pressing (ECAP) at 873 K, alpha-phase grains were markedly
refined from 11 μm to ≈ 0.3 μm, and misorientation angle was increased. Uniaxial-tension tests were
conducted for initial coarse grained (CG) and two UFG alloys (ε = 4 and 8) at temperature of 973 K
and strain rate of 10-4 s-1. Quantitative measurements of cavitation evidenced that both the average
size and the area fraction of cavities significantly decreased with decreasing grain size and/or
increasing misorientation. It was also found that, when compared to CG alloy, cavitation as well as
diffused necking was less prevalent in UFG alloys, which was presumably due to the higher value of
strain-rate sensitivity. Based on the several theoretical models describing the cavity growth behavior,
the cavity growth mechanism in UFG alloys was suggested.
Heat Conduction of 2D Composite Materials with Symmetric Inclusions: a Model and Reduction to a Vector-Matrix Problem
Authors: Dubatovskaya Marina , Rogosin Sergei
Published: March 2009

We consider steady potential heat conduction of a cylindrical composite material
with the special geometry. The matrix is modelling by the unit disc with di®erent conductivity
of six equal sectors. Inclusions (having di®erent conductivity too) are symmetrically situated
discs non-intersecting boundary of sectors. Mixed boundary conditions on parts of the boundary
of matrix and matrix-inclusions leads to di®erent model of composite materials. A new method
to study the corresponding mathematical model is proposed. It is based on the reduction of
the problem to the vector-matrix boundary value problem for analytic vectors. The method is
connected with the approach by Zhorovina and Mityushev to the study of R-linear boundary
value on a fan-shaped domain.
Numerical Analysis of Triaxial Residual Stresses in Quenched 316H Stainless Steel
Authors: Andrade Campos A. , Teixeira Dias Filipe
Published: March 2009

Residual stress fields can cause creep damage in thermally aged components, even in the
absence of working loads. In order to study this issue, the authors present a numerical study on the
development of triaxial residual stresses in stainless steel specimens. A mechanical model dedicated
to the analysis of heat treatment problems is described. The presented formulations are implemented
incrementally with a non-linear constitutive model, adequate to the simulation of a wide range of
thermal processes. The flow rule is a function of the equivalent stress and the deviatoric stress
tensor, of the temperature field and of a set of internal state variables. The thermomechanical
coupled problem is solved with a staggered approach. Spray water quenching was used to generate
residual stress fields in solid cylinders and spheres made from 316H stainless steel. Finite element
simulations were performed to find out how process conditions and specimen geometry influence
the resulting residual stress distributions. The results show that compressive residual stresses are
developed near the surfaces of the cylinders and spheres while tensile residual stresses occur near
the centre. The level of residual stresses was found to be dependent on the heat transfer coefficient.
Oxynitride Research in the Nano Era
Authors: Thompson Derek P.
Published: March 2009

Research in nitrides and oxynitrides has experienced a significant downturn during the last 10 years – perhaps because there have been fewer new developments in the R. & D. field compared with the regular new initiatives reported in the 1980s and early 1990s, but also because the public perception is now very much that research issues associated with commercial nitride materials have been “worked out”. With the limited market (both in volume and price) for structural materials, funding bodies are tending to direct their resources into other research areas where it is perceived there are more opportunities and a larger market place. lnfluenced by these trends, new researchers at the start of their careers are tending to focus their research on other areas of ceramics or materials science, rather than striving to find new developments in what may be seen as a “worked-out” subject area. This is not to say that there is not still a considerable amount of research that can be done in the nitrides/oxynitrides field, but radical new ideas are needed, focused on topical and appreciably-sized market applications, in which the portfolio of properties offered by oxynitrides demonstrates clear advantages over cheaper and more easily prepared alternatives.
The Intergranular Oxynitride Microstructure in Silicon Nitride Based Ceramics
Authors: Falk L.K.L. , Schneider N. , Menke Yvonne , Hampshire Stuart
Published: March 2009

The intergranular microstructure in a liquid phase sintered silicon nitride based ceramic may be viewed as an oxynitride glass-ceramic. This work is concerned with the incorporation of yttrium B-phase, which is a five-component phase, into the intergranular regions of silicon nitride ceramics. The silicon nitride materials were fabricated with the addition of a powdered B-phase parent glass with composition (e/o) 35Y:45Si:20Al:83O:17N, or the addition of a mixture of Y2O3, SiO2 and Al2O3 with cation composition (e/o) 35Y:45Si:20Al. The starting powder mixtures contained 10 wt% of sintering additives. Sintering for 2 h at 1800°C was followed by a two-step post-densification heat treatment in order to promote nucleation and growth of yttrium B-phase. Detailed imaging and elemental analysis of the intergranular regions was carried out by EDX in a FEGTEM.
Modeling Recrystallization in Aluminum Using Input from Experimental Observations
Authors: Brahme Abhijit P. , Fridy Joseph M. , Rollett Anthony D.
Published: March 2009

A model has been constructed for the microstructural evolution that occurs during the annealing of aluminum alloys. Geometric and crystallographic observations from two orthogonal sections through a polycrystal using automated Electron Back-Scatter Diffraction (EBSD) were used as an input to the computer simulations to create a statistically representative threedimensional model. The microstructure is generated using a voxel-based tessellation technique. Assignment of orientations to the grains is controlled to ensure that both texture and nearest neighbor relationships match the observed distributions. The microstructures thus obtained are allowed to evolve using a Monte-Carlo simulation. Anisotropic grain boundary properties are used in the simulations. Nucleation is done in accordance with experimental observations on the likelihood of occurrences in particular neighborhoods. We will present the effect of temperature on the model predictions.
Generalized Vertex Model - Study of Recrystallization in Copper
Authors: Piękoś Krystian , Tarasiuk Jacek , Wierzbanowski Krzysztof , Bacroix Brigitte
Published: March 2009

Classical vertex model till now described only the grain growth stage and not the primary recrystallization. In the present work the vertex model is first extended in order to take into account the both stages of recrystallization process. The influence of the stored energy is taken into account and some phenomenological laws describing the evolution of grain boundary energy and mobility with misorientation angle are used. Nucleation is considered to be site-saturated. The experimentally determined stored energy values, crystallographic orientations and boundary misorientation distributions are used in order to characterize the initial microstructure. The model is tested to study the recrystallization of 70% and 90% cold rolled polycrystalline copper during an annealing treatment. In order to explain the texture evolution in both cases, it is necessary to introduce an energy threshold for grain boundary movement, i.e. a minimal value of the stored energy difference between a nucleus and the deformed material necessary to provoke grain boundary motion. The developed model is shown to predict texture evolutions in good agreement with experimental data.
Simulation of Ideal Grain Growth Using the Multi-Phase-Field Model
Authors: Schaffnit Philippe , Apel Markus , Steinbach Ingo
Published: March 2009

The kinetics and topology of ideal grain growth were simulated using the phase-field model. Large scale phase-field simulations were carried out where ten thousands grains evolved into a few hundreds without allowing coalescence of grains. The implementation was first validated in two-dimensions by checking the conformance with square-root evolution of the average grain size and the von Neumann-Mullins law. Afterwards three-dimensional simulations were performed which also showed fair agreement with the law describing the evolution of the mean grain size against time and with the results of S. Hilgenfeld et al. in 'An Accurate von Neumann's Law for Three-Dimensional Foams', Phys. Rev. Letters, 86(12)/2685, March 2001. Finally the steady state grain size distribution was investigated and compared to the Hillert theory.
Characteristic Microstructure Evolution of Polycrystalline Ag Films Prepared from Ink-Jetted Ag Nanoparticle Suspension
Authors: Jung Jung Kyu , Choi Soo Hong , Jang Myoung Joon , Joung Jae Woo , Joo Young Chang
Published: March 2009

Use of silver (Ag) nanoparticle suspension for various applications such as ink-jet
printing of electronic circuits has been of prime interest. We observed the microstructure evolution
of the inkjet-printed Ag thin films on Si substrates under various annealing conditions using the
field-emission scanning electron microscopy (FE-SEM). Abnormal grain growth characteristics
were identified when annealed at about 240 oC under ambient air. Growth characteristics of pores
were found to be in accordance with that of grains. Competition between grain and pore growth is
attributed to small grain sizes, low packing density and high porosity, which are characteristic of
inkjet-printed Ag films as dried.
Devitrification and High Temperature Properties of Mineral Wool
Authors: Nielsen Eva Ravn , Augustesen Maria , Ståhl Kenny
Published: March 2009

Mineral wool products can be used for thermal and acoustic insulation as well as for fire
protection. The high temperature properties and the crystallization behaviour (devitrification) of the
amorphous fibres during heating have been examined.
Commercial stone wool and commercial hybrid wool (stone wool produced by a glass wool
process) have been compared, as well as specially produced stone wool fibres. The fibres differed in
chemical compositions and degree of oxidation given by Fe3+/Fetotal ratios.
The materials were studied by thermal stability tests, X-ray diffraction, Mössbauer spectroscopy,
secondary neutral mass spectroscopy, differential scanning calorimetry and thermal gravimetric
analysis.
When stone wool fibres were heated at 800 °C in air, oxidation of Fe2+ to Fe3+ occurred
simultaneously with migration of divalent cations (especially Mg2+) to the surface. Decreasing
Fe3+/Fetotal ratios resulted in increasing migration and improved thermal stability. The cations
formed a surface layer mainly consisting of MgO.
When heated to above 800 °C, bulk crystallization of the fibres took place with diopside and
nepheline as the main crystalline phases.
Commercial stone wool and the specially made fibres were considerably more temperature stable
than the commercial hybrid wool. Commercial hybrid wool has a high Fe3+/Fetotal ratio of 65%
resulting in less migration of cations during heat treatment.
Magnetic and Structural Properties of Nitrified FINEMET Powder Using by Mechanical Milling Method
Authors: Hong Seong Min , Kim Cheol Gi , Kim Chong Oh
Published: March 2009

The magnetic and structural properties of FINEMET [Fe73.5Si13.5B9Nb3Cu1 wt %]
amorphous powder were investigated after nitrification and mechanical milling. Fe-based
amorphous powder were nitrified and crystallized simultaneously at 550°Cusing by ammonia(NH3)
gas. Nitrified powder exhibited iron nitride phase such as γ′-Fe4N, Fe3N and α″-Fe16N2. Nitrified
particles were more brittle than raw particles. As a result, nanometer sized nitride powder were
fabricated by high energetic ball milling method. The saturation magnetization(Ms) and
coercivity(Hc) of nitrified powder were increased due to nitride phase.
Crystallization Kinetics and Texture Evolution in Iron-Based Amorphous Alloys under a Magnetic Field
Authors: Tsurekawa Sadahiro , Fujii H. , Yardley V.A. , Matsuzaki T. , Watanabe T.
Published: March 2009

Crystallization kinetics and texture evolution in iron-based amorphous alloys (Fe78Si9B13, Fe73.5Si13.5B9Nb3Cu1) under a magnetic field have been studied. We have found that the application of a magnetic field during crystallization at a temperature ranging the Curie point of the amorphous phase and that of the crystalline bcc-Fe(Si) phase can produce a {110} texture in the alloys. X-ray diffraction with the Schulz method revealed that {110} oriented grains were preferentially nucleated due to the magnetic field. The studies of crystallization kinetics found that the nucleation rate of the α-Fe(Si) phase in amorphous Fe73.5Si13.5B9Nb3Cu1 was enhanced approximately three times as high with the 6T magnetic field than without field. The volume fraction of crystalline α-Fe(Si) phase produced was increased by the magnetic field.
Submicrocristalline Structure in Copper after Different Severe Plastic Deformation Schemes
Authors: Dobatkin Sergey V. , Salishchev Gennady A. , Kuznetsov A.A. , Kon'kova T.N.
Published: March 2009

The structure and properties of oxygen-free copper (99,98%) were studied after different
types of severe plastic deformation (SPD): equal-channel angular pressing (ECAP), multiaxial
deformation (MD), and accumulative roll bonding (ARB) as a function of the strain at room
temperature (to a true strain of 30-40). The SPD facilitates the formation of submicrocrystalline
structure with a grain size of 200-250 nm and predominantly high angle boundaries (83-94%). ECA
pressing leads to the formation of the most uniform submicrocrystalline structure.The strength
characteristics increase with increasing strain and reach the steady stage at ε ≈ 5. At the steady
stage, UTS = 460-480 MPa at ARB, and MD, while UTS at ECAP is somewhat lower, 430-440
MPa. The smallest "steady" values EL = 4 - 5% were obtained in the case of ARB, and the
maximum EL = 18% was obtained at MD.
Annealing Effects on Mechanical Properties and Microstructure of AZ31 Alloy Sheet Differential-Speed-Rolled at Low Temperatures
Authors: Jeong Y.G. , Kim Woo Jin , Choi Seo Gou , Jeong Ha Guk
Published: March 2009

For the Magnesium alloy AZ31, hot rolling is usually carried out in the temperature range between 250 and 400°C but the processed sheets usually exhibit high anisotropy in mechanical properties. In the current study, DSR process was found to be effective in improving anisotropy of mechanical properties and ductility at room temperature. Full recrystallization takes place from 200°C and above. A large drop of UTS occurs above 200°C where full recrystallization starts. Tensile elongation increases with annealing temperature but anisotropy degrades from 200°C onwards. Texture change during recrystallization is believed to be responsible for this result.
In Situ EBSP Observations of Recrystallization in Commercial Purity Aluminum
Authors: Kajihara Katsura
Published: March 2009

This study presents in-situ EBSP observations of recrystallization in commercial purity
aluminum sheets with different concentrations of solutes and different states of precipitation. The
in-situ observations demonstrate clearly the behaviors of the nucleation and growth of recrystallized
grains, and the movements of grain boundaries at an early stage of recrystallization. The high mobility
of grain boundaries neighboring the deformed matrix was generally observed presumably due to
strain-induced grain boundaries migration. The grain boundary motion was also found to strongly
depend to the solute content level. These in-situ observations provide important evidence to show that
the behaviors of grain boundary motion at an early stage of recrystallization leads to the grain size
distribution and the curvature of grain boundaries after the primary recrystallization.
Recrystallization Deformation of Austenite, Microstructure of Martensite and Property of Rolled Steel Products
Authors: Traino A. , Baschenko A. , Ivoditov Vadim , Zavrazhnov A. , Knokhin V.
Published: March 2009

Novel technological processes for conceptually new integrated deformation-thermal
production of flat rolled stock with enhanced physical-mechanical properties and minimized
alloying system have been devised on the basis of recently discovered metallophysical laws of
influence, through hot plastic deformation by rolling, upon microstructure-phase conversions and
states of steel in metallurgical products.
Model Alloys to Study the Solute Drag and Precipitation Effect on the Recrystallization Kinetics of Nb-Microalloyed Steels
Authors: Vervynckt Stephanie , Thibaux Philippe , Liebeherr Martin , Houbaert Yvan
Published: March 2009

A good combination of strength and toughness in HSLA steels can be achieved by the addition of microalloying elements such as Nb. Nb can retard the static recrystallization of austenite at low temperatures by either a solute drag or by a precipitation pinning (when bonded to C or N) effect. Both mechanisms result in improved mechanical properties due to grain size refinement of the transformed ferrite. In this study, 3 Nb-microalloyed model alloys were designed to investigate the solute drag and the precipitation effect separately. The first alloy, containing a stoechiometric ratio of Nb and C, was designed to study the retarding effect of NbC on the recrystallization behavior. A second alloy, containing Nb and only few ppm C, was casted in order to study the effect of Nb in solid solution. The two alloys were compared with a C-Mn reference alloy. The recrystallization behavior of the three alloys were compared by multi-hit torsion tests and double hit compression tests. The Nb-C and the Nb-very low C showed small differences in recrystallization behavior. These results show that Nb delays the recrystallization by a solute drag effect or by the formation of a very small amount of precipitates.
Dynamic Recrystallization in Copper and Copper-Tin Alloys
Authors: McDonald D.T. , Humphreys John F. , Bate Pete S. , Brough Ian
Published: March 2009

Copper, Cu-2%Sn and Cu-4.5%Sn alloys have been deformed in plane strain compression at temperatures up to 700oC and the evolution of the microstructures and textures determined by high resolution EBSD. The effect of the solute is to raise the temperature at which dynamic recrystallization occurs and to significantly reduce the size of the dynamically recrystallized grains. In all the materials, there is a small increase in the cube texture component on dynamic recrystallization. The boundary bulges which precede recrystallization are different in the copper and Cu-Sn alloys, although in both materials there is evidence that local deformation in the boundary regions plays a significant role in dynamic recrystallization.
Atomistic Processes of Phase Transformation and Dynamic Recrystallization during Hot-Working of Intermetallic Titanium Aluminides
Authors: Appel Fritz , Oehring Michael , Paul Jonathan H.D.
Published: March 2009

Intermetallic titanium aluminide alloys are multiphase assemblies with complex microstructure and constitution, involving the phases γ(TiAl), α2(Ti3Al), β, and B2. The earlier stages of phase transformation and dynamic recrystallization occurring upon hot-working of such an alloy were investigated at the atomic scale by high-resolution electron microscopy. Accordingly, the conversion of the microstructure is triggered by heterogeneities in the deformation state and non-equilibrium phase composition. The β/B2 phase is apparently unstable under tetragonal distortion, which gives rise to the formation of the B19 phase via distinct shuffle displacements. These processes lead to a modulated microstructure, which is comprised of several stable and metastable phases. The phase transformations are accomplished by the propagation and coalescence of ledges. Large and broad ledges can apparently easily be rearranged into intermediate metastable structures, which serve as precursor for the nucleation of new grains.
Boundary Migration Induced Plasticity during Recrystallization and Growth under Applied Stress
Authors: Kim Se Jong , Cho Yi Gil , Suh Dong Woo , Kim Sung Joon , Kim Gyo Sung , Han Heung Nam
Published: March 2009

In general, plastic strain occurs over a certain stress, called yield stress. However, it has been
reported that the permanent strain could happen during boundary migrating even under the
extremely slight externally applied stress. In this study, we performed dilatometry experiments
under the various compressive stresses and measured the amount of recrystallization and growth
induced permanent strain. A new empirical constitutive equation was suggested to describe the
recrystallization and growth induced plasticity. This equation was verified by comparing the
calculated values with dilatometric experimental data under the various compressive stresses.
Effect of Austenite as a Harder Second Phase on Ferrite Substructure Evolution by Intercritical Rolling
Authors: Yokota T. , Ohtsubo H. , Endo S.
Published: March 2009

Effect of austenite as a harder second phase on ferrite substructure evolution by intercritical
rolling has been investigated using 0.12C-0.3Si-1.35Mn steel. Slab was reheated at 780°C (ferrite; α +
austenite; γ phase region) and rolled with 90% reduction down to 12mm in thickness using laboratory
mill. 700°C (ferrite; α + cementite; θ phase region) rolled plate was also prepared to compare with 780°C
rolled plate. Microstructure distribution along the plate thickness has been observed in detail by SEM
and EBSD. Microstructure showed mixed structure of fine-grained ferrite and elongated ferrite for both
of the plates. The ratio of fine-grained ferrite region was around 50% at the plate surface, however,
fine-grained ferrite formation hardly occurred at mid thickness for 700°C rolled plate. FEM analysis
revealed that fine-grained ferrite distribution along the thickness can be well explained by equivalent
plastic strain distribution along the plate thickness for 700°C rolled plate. Equivalent plastic strain
showed maximum value near the plate surface due to shear strain component, and it could help
substructure evolution and fine grained ferrite formation. On the other hand, the ratio of fine-grained
ferrite region reached to 50% all through the thickness for 780°C rolled plate. Austenite as a harder
second phase seems to promote ferrite substructure evolution even at mid thickness of the plate.
Texture Development in 6000 Series Al-Mg-Si Alloys for Car Body Panels
Authors: Inagaki Hirosuke
Published: March 2009

Recovery, recrystallization and the formation of recrystallization textures were investigated in three representative Al-Mg-Si alloys used for car body panels. Commercial hot bands of AA6016, AA6111 and AA6061 Al-Mg-Si alloys finished at low temperatures were cold rolled to a rolling reduction of 95 % in thickness and isothermally annealed at temperatures between 250 and 500 °C. In these alloys, precipitation was completed for the most part during low temperature hot rolling, and the sizes and the amount of fine precipitates formed during this low temperature hot rolling strongly affected recrystallization and the development of recrystallization textures. As a result, in the specimens annealed at 300 °C, quite different recrystallization behavior and recrystallization textures were observed. In the AA6061 alloy, in which, among three alloys, the maximum amount of Mg2Si should be precipitated, recrystallization was significantly suppressed. This resulted in the formation of strong {110} <111> and {100} <013> recrystallization textures. Also in the AA6111 alloy, in which precipitation of a medium amount of Mg2Si was expected, recrystallization was retarded to the same extent. In this alloy, however, recrystallization textures consisted of very strong {100} <001> and rather strong {110} <111> main orientations. In theAA6016 alloy, in which the minimum amount of Mg2Si and a large amount of Si particles should be precipitated, recrystallization occurred very rapidly, forming very weak recrystallization textures. In all alloys, annealing at higher temperatures resulted in the formation of weak textures, since fine precipitates were dissolved during annealing. Thus, the solution treatment, which is a necessary step to induce bake hardening in these alloys, randomizes their recrystallization textures.
Effect of Processing Order on Strengthening of Friction Stirred Mg-Y-Zn Alloy
Authors: Tsujikawa Masato , Tanaka Maho , Morishige Taiki , Chung Sung Wook , Oki Sachio , Higashi Kenji
Published: March 2009

High-strength Mg-Y-Zn alloy plate was obtained by friction stir processing (FSP) after casting. In this study, the effect of processing order on the strength of processed specimens was discussed. It was revealed that the microstructures and strength of doubly stirred zone depended on the direction of overlapping pass. In the area of the doubly stirred zone that was affected by the thermal history of Retreating-side, the hardness was 121Hv. It was twice as hard as Base Metal, and harder than the doubly stirred zone that was affected by thermal history of Advancing-side.
Effect of Stacking Fault Energy on Evolution of Recrystallization and Grain Growth Textures of Metals
Authors: Lee Dong Nyung
Published: March 2009

The drawing textures of aluminum, copper, gold, silver, and Cu-7.3% Al bronze wires are approximated by major <111>+minor <100>, except silver wire, which can have the <100> texture at extremely high reductions. The <111> component in the drawing textures of aluminum, copper, gold, and silver transform to the <100> component after recrystallization. On the other hand, the <111> deformation texture of the Cu-7.3% Al bronze wire, which has very low stackingfault- energy, remains unchanged after recrystallization. The <100> + <111> recrystallization textures change to the <111> texture after abnormal grain growth. The Brass component {110}<112> in rolling textures of high stacking-fault-energy metals such as aluminum, copper, Cu- 16% Mn, and Cu-1% P changes to the Goss orientation {110}<001> after recrystallization. However, the Brass orientation in rolling textures of low stacking-fault-energy fcc metals such as brass and silver appears to change to an orientation approximated by the {236}<385> orientation after annealing. The texture changes are discussed based on the strain-energy-release-maximization model for medium to high stacking-fault-energy metals and on grain growth for low stacking-fault energy metals.
Grain Growth, Microstructure and Property of Ultrafine WC-Co Alloy by Spark Plasma Sintering
Authors: Sun Lan , Jia Cheng Chang , Xian Min , Cao Rui Jun
Published: March 2009

In order to control WC grain size and get a microstructure with fine grain size during the sintering process, WC grain growth in WC-Co cemented carbide was investigated. The possible reason on the grain growth was showed which includes the normal grain growth (NGG) and the abnormal grain growth (AGG). We adopted the SPS (spark plasma sintering) to sinter nanometer WC-Co powder, the range of temperature was 1100 -1250 °C, the pressure was 40MPa, and sintering time was 5min. In this paper, we discuss the density, hardness, microstructures and grain sizes of the sintered samples. The results showed that during the process sintering WC-Co powder, there are two kinds of growths. XRD investigation of the WC–Co samples spark plasma sintered to full density revealed that no new phase was created. Through the observed microstructure of the sintered samples, we analyzed the reason of the abnormal grain growth of WC grain. The density and hardness of samples were increased with increasing temperature.
Synthesis of Si3N4 from Na2SiF6 as a Solid Precursor: Thermodynamic Study
Authors: Leal-Cruz Ana Lilia , Pech-Canul Martin I.
Published: March 2009

CVD silicon nitride (Si3N4) is typically produced from gas or liquid precursors
containing nitrogen and silicon. The method using Na2SiF6(s) as silicon solid precursor to produce
films/coatings, reinforcements and powders of silicon nitride by CVD has been recently proposed in
the literature. In this investigation, a thermodynamic study is carried out using the FactSage
Thermochemical Software and Databases, in order to explain the phenomena associated to the
synthesis of Si3N4 with Na2SiF6 as solid precursor. Accordingly, CVD diagrams for Na2SiF6, SiF4,
SiF3, SiF2, SiF, and Si both with N2 and NH3 are constructed using such a software.
Thermodynamically Si3N4 can be produced from SiF4(g) or Na2SiF6(s) with ammonia. Although
thermodynamic considerations show that Si3N4 cannot be produced with the use of nitrogen,
experimental results in this investigation show that it is formed with both ammonia and nitrogen.
Sintering + HIP of Ultrafine WC-Co Hardmetals
Authors: Ordóñez A. , González R. , Sánchez J.M.
Published: March 2009

This work analyses the changes induced on the microstructure and mechanical properties of ultrafine (0.2 and 0.4 μm) hardmetal grade WC-7wt.% Co by HIP after vacuum sintering. A large HIP pressure (155 MPa) is applied to the ultrafine hardmetal system at different temperatures (1000, 1200 and 1400 °C). The well-known correlation between porosity reduction and fracture strength improvement is confirmed. Residual porosity left after liquid phase sintering is removed more effectively at HIP temperatures above the eutectic point of the alloy (1400 °C). In the absence of grain growth inhibitors, hardness decreases continuously, and WC-Co ultrafine microstructure coarsens as HIP temperature rises. However, for specimens containing VC and Cr3C2 additions, hardness increases as HIP temperature rises from 1200 to 1400 °C. It is proposed that this anomalous trend (confirmed by grain size observations) is related to the activation of coalescence mechanisms during solid state HIPing, which are inhibited by the presence of a liquid phase.
Thixotropic Behaviour of a Cu – Eutectic Sn-Pb Slurry
Authors: Merizalde Carlos , Cabrera Jose María , Prado Jose Manuel
Published: March 2009

Semi-solid materials (SSM) in the thixotropic state behave like liquids, i.e they show low or null shear resistance and, at the same time, they behave like solids as do not fall to pieces under applied forces. At present, the potential advantages and industrial applications of these materials are well recognized, in particular for the production of Al-alloy components for the aerospace and automotive sectors. This work is focused on the evaluation and characterization of the thixotropic behaviour of a metal mixture in the semi-solid state obtained by “Compocasting”. The mixture is obtained by mixing spherical solid Cu particles with a liquid eutectic tin-lead alloy. Measurements of the time-dependence of the viscosity of the mixture using an instrumented rheometer showed that, after mechanical stirring, the slurry acquires thixotropic properties. The best conditions to obtain such mixture are presented. Additionally, once the mixture is cooled down, the material is reheated and then tested in a laboratory backward extrusion process. The behaviour of the material is analysed on the basis of the microstructure obtained, and the process parameters considered.
In Vitro Bioactivity Assessment of Ceramics in the SiO2–CaO–MgO System
Authors: Bretado-Aragón Luis A. , Cortés-Hernández Dora A. , Escobedo-Bocardo José C. , Almanza-Robles J.M. , Escalante G. J.Ivan
Published: March 2009

Both solid-state reaction and glass-ceramic methods are used to obtain bioactive materials (CaSiO3) with different concentrations of MgO (6, 8, and 10 wt %) on the basis of the stoichiometric composition of CaO·SiO2. The in vitro bioactivity assessment is performed by immersing samples in SBF (simulated body fluids) for different periods of time. The analysis of the materials before immersion indicates the presence of different phases (akermanite, wollastonite and diopside) in the materials obtained by the solid state reaction method. It is possible to obtain wollastonite with incorporation of magnesium in its structure ((Ca, Mg)·SiO6) by the glass-ceramic method. The results obtained after immersing the samples in SBF indicate that a Ca, P-rich layer is formed on all the materials tested, even in those containing a high quantity of MgO. However, the layer formed in the MgO-free CaSiO3 ceramic is thicker than that formed in the MgO-containing materials.
A Study of hBN-Y2O3 Composite Investment for Casting Ti-6Al-4V Alloy
Authors: Shen Bin , Liu Hong Bao , Mao Xie Min , Li Chong He
Published: March 2009

An hBN-Y2O3 composite investment moulding material was developed for investment
casting Ti-6Al-4V alloy. Hexagonal boron nitride (hBN) powders plus a few Y2O3 powders were
used as the investment mould material to prepare the shell mould with colloidal yttria as binder. The
results show that the hBN-Y2O3 composite investment mould can be used to cast Ti-6Al-4V alloy,
and has lower cost compared with the traditional yttria based investment mould, because of
chemically inert of hexagonal boron nitride and its lower density. Moreover the interfacial reaction
between the Ti and hBN-Y2O3 composite shell mould was investigated with measurement of
microhardness and scanning electron microscopy (SEM) with energy dispersive (EDS).
The Effect of Heat Treatment on the Microstructure and Mechanical Properties of Laser Rapid Forming Ni-Based Alloy Rene88DT
Authors: He Fei , Chen Jing , Zhao Xiao Ming , Lin Xin , Xu Xiao Jing , Huang Wei Dong
Published: March 2009

Laser rapid forming (LRF) is introduced as a novel fabrication process for Ni-based
superalloy Rene88DT. The effect of heat treatment parameters of quenching rate and aging time on
size and distribution of γ′ precipitation was investigated. The heat treatment parameters were first
determined by DSC, and then optimized based on the examination of the microstructure and
mechanical properties of heat treated LRF Rene88DT. The experimental results show that, the
precipitation of γ′ is inhomogeneously distributed as a result of uneven heat-cycle during LRF in
as-deposited Rene88DT, resulting in low mechanical properties. After being heat treated at 1165°C,
2h/AC + 760°C,28h/AC, γ ′ precipitation are homogeneously distributed with the size of 40~60nm,
and the tensile strength of heat treated sample shows an increase of 400MPa as compared to that for
as-deposited. The yield strength is close to that of the PM+HIP standard.
Onset Magnetic Field for Rearrangement of Martensite Variants in Ni2MnGa
Authors: Fukuda Takashi , Okamoto Nariaki , Kakeshita Tomoyuki
Published: March 2009

The magnetic field strength, Hs, at which rearrangement of martensite variants initiates
has been investigated in Ni2MnGa ferromagnetic shape memory alloy by magnetization
measurements in the [001]P direction ("P" stands for the parent phase). We have also calculated Hs
from the magnetocrystalline anisotropy constant Ku, spontaneous magnetization Ms, twinning shear
s and twinning stress τreq by considering the condition for the rearrangement of martensite variants
reported previously [Int. J. Appl. Electromagnetics and Mechanics, 23 (2006) 45]. The calculated
value of Hs is in good agreement with the experimental value for all the examined temperatures.
The agreement confirms the applicability of the reported condition.
An Actuator Laser of Optical Disk Drive High-Frequency Electromagnetic Vibrations Characteristic Analysis
Authors: Wu Lan Ying , Ban Huai Guo , Deng Jing , Guo Rui
Published: March 2009

The actuator has widely used in CD and DVD system it have more application foreground
in the future, but nonlinearity and creep exist in the actuator, which limit actuator application in high
capacity, high redundancy, high transfer rate and short access time system. In this paper, we give a
detail introduction on the actuator laser of optical disk high-frequency electromagnetic vibrations
characteristic.
Nanowire Fabrication of Silicon-Based Materials
Authors: Kohno Hideo , Takeda Seiji
Published: March 2009

This paper describes our recent achievements in fabricating various kinds of nanowires of
silicon-based materials including beta iron-silicide, silicon carbide, and silicon germanium. Some of
them can be grown directly at one-step process, while the others can be fabricated using nanowire
templates. We discuss their structures, growth mechanisms, and properties based on electron
microscopy observations.
Ternary Sm-Al-Co Bulk Metallic Glass Formation Designed Using a Cluster Line Approach
Authors: Wu Jiang , Wang Qing , Li Yan Hui , Qiang Jian Bing , Wang Ying Min , Dong Chuang
Published: March 2009

Ternary Sm-Al-Co bulk metallic glass formation is investigated with the guidance of a
cluster line approach which is defined by linking a special cluster composition to the third element in
the ternary phase diagram. Two dense-packed cluster lines Sm6Al3Co2-Co and Sm8Al1Co4-Al are
constructed and they intersect at a good BMG composition Sm50Al25Co25. This composition can also
be interpreted with a cluster-plus-glue atom model. The characteristic parameters of this optimum
BMG are respectively Tg = 579 K, Tx = 640 K, Trg= 0.648, γ = 0.435 and E=244 kJ/mol.
Cluster-Based Bulk Metallic Glass Formation in Co (-Fe)-Si-B-Nb Alloy Systems
Authors: Wang Qing , Zhu Chun Lei , Li Yan Hui , Wu Jiang , Dong Chuang , Qiang Jian Bing , Zhang Wei , Inoue Akihisa
Published: March 2009

The present paper investigates the bulk metallic glass formation in Co-based alloy systems
with the guidance of the cluster line and minor-alloying principles. The selected basic ternary Co-B-Si
alloy compositions are intersecting points of cluster lines, defined by linking special binary clusters to
the third element. Then these basic ternary alloys are further minor-alloyed with Nb and quaternary
bulk metallic glasses are obtained only by 4-5 at. % Nb minor-alloying of the basic composition
Co68.6B25.7Si5.7 that is developed from dense-packed cluster Co8B3. The bulk metallic glasses are
expressed approximately with a unified simple composition formula: (Co8B3)1(Si,Nb)1. In addition, a
quantity of Fe substitution for Co further improves the glass-forming abilities.
Shear Banding Analyses of Amorphous Alloys with Crystalline Particles
Authors: Shibutani Yoji , Park Jun Young , Wakeda Masato
Published: March 2009

Plastic deformability of the binary (copper and zirconium) amorphous alloy with
embedded nanosized crystals under uniaxial tension and compression is analyzed using molecular
dynamics simulations. The number and the size of the nanocrystals are taken as the study
parameters. The number of nanocrystals affects the distribution of defects, that is, shear bands
nucleation and thus changes the stress-strain curve, whereas the size of the nanocrystals does not
significantly influence the response. As already reported in the experimental works, coalescent
voids are found under tension in the shear bands or at the interface between crystalline and
amorphous phases. This suggests that much attention should be paid to the interface strength around
the particles.
Rolling Texture of α"-Phase in Ti-22mol%Nb-3mol%Al Biomedical Shape Memory Alloy
Authors: Inamura Tomonari , Shimizu Ryutaro , Kim Jae II , Kim Hee Young , Wakashima Kenji , Miyazaki Shuichi , Hosoda Hideki
Published: March 2009

Rolling texture of α"(C-orthorhombic) martensite phase in Ti-22mol%Nb-3mol%Al
β-titanium based shape memory alloy was examined using X-ray pole figure measurement. The alloy
was dual phase of α'' and β(bcc) at room temperature (RT) and was cold-rolled with reduction rates of
40%~99% at RT. Stress-induced martensitic transformation occurred during the rolling and then the
material was fully transformed into martensite phase. Subscript α" and β indicate martensite and
parent phase hereafter. The major texture was close to {411}α"<173>α" when the reduction rate was
lower than 60%. This texture is a result of a preferential formation of specific variants which have a
higher interaction with the macroscopic deformation. As the reduction rate was increased, ND moved
toward {101}α" whereas RD was around <010>α" regardless of the reduction rate. {101}α"<010>α"
texture was confirmed when the reduction rate was 99%.
Silk as Substratum for Cell Attachment and Proliferation
Authors: Chirila Traian V. , Barnard Zeke , Zainuddin Z. , Harkin Damien
Published: March 2009

Silk fibroin (SF), isolated from silkworm (Bombyx mori) cocoons, is a natural
biodegradable polymer. Over the past decade, there was some interest in using SF as a biomedical
material. As part of a project to develop tissue-engineered constructs for the surgical restoration of
the ocular surface (cornea, conjunctiva), we have investigated the capacity of SF to function as a
substratum for the attachment and growth of corneal stem/progenitor cells harvested from the
corneoscleral limbus of donor human corneal tissue. SF membranes were produced from cocoons
following a protocol involving successive dissolution steps, filtration, dialysis, evaporation, and
methanol treatment. Human limbal epithelial cells were harvested from donor tissue and seeded
onto SF membranes. After 5 days, the culture was fixed and stained with specific agents to visualize
the cells. The study indicated profuse cellular attachment and growth. SF membranes appear to be
suitable as a substratum for the repair of damaged ocular surface.
Effect of Small Amount of Dopant on Phase Stability of Zirconia Bioceramics
Authors: Takigawa Yorinobu , Uesugi Tokuteru , Higashi Kenji
Published: March 2009

The effect of small amount of cation dopant on phase stability of zirconia bioceramics is
evaluated by ageing in hot water. The phase transformation progresses with time in all specimens.
However, the tetragonal to monoclinic transformation behavior is much different depending on the
dopant. In case that the small amount of tetravalent soluble element is added, the transformation is
promoted if the ionic radius of the element is larger than that of zirconium, and the transformation is
suppressed if the element with smaller ionic radius than zirconium ion is added, which is explained
from the change in the axial ratio, c/a. However, the change in phase stability of 7.7mol%TiO2-doped
TZP cannot be simply explained from the change in the axial ratio, c/a. XRD analysis reveals that the
distance between nearest neighbor anion and cation site significantly decreases only in
7.7mol%TiO2-doped TZP. This result indicates that the binding energy between dopant and oxygen
vacancy affects the phase stability as well as the change in the axial ratio, c/a.
Self-Propagating High-Temperature Synthesis of Porous Nickel-Titanium
Authors: Ayers Reed , Ferguson Virginia , Belk Denise , Moore John J.
Published: March 2009

Porous equiatomic Nickel-Titanium (NiTi) is a strong candidate material for bone engineering
applications because its mechanical properties are within the range of bone and its porosity allows
for biologic interlock of the material to the surrounding tissue. Self-propagating high-temperature
synthesis (SHS) is one method for producing porous NiTi. Nickel and titanium powders, -325 mesh,
were mixed for 24 hours then pressed into cylindrical pellets (0.5 inch diameter, 0.5 inch height) to
a theoretical green density of approximately 53%. The pellets were preheated in flowing argon for
one hour then ignited using a tungsten coil. Scanning electron microscopy and electron dispersive
spectroscopy (EDS) show localized differences of stoichiometry suggesting variations in the crystal
structure where the Ni to Ti atomic ratio varied between 48.5:51.5 and 50.7:49.3. X-ray diffraction
(XRD) (Philips X’Pert PRO) confirmed the presence crystalline equiatomic NiTi as well as other
intermetallic compounds including NiTi2 and Ni4Ti3. Nanoindentation (MTS Nano Indenter XP) of
this heterogeneous material indicates a mean range indentation modulus of 89.6 ± 9.4 GPa. This is
on the same order of magnitude as bone, which has an elastic modulus range of 14-20 GPa.
Fatigue Strength of Lotus-Type Porous Magnesium
Authors: Seki Hironori , Tane Masakazu , Nakajima Hideo
Published: March 2009

We studied the fatigue strength of lotus-type porous magnesium with cylindrical pores
aligned unidirectionally, which was fabricated through unidirectional solidification in pressurized
hydrogen atmospheres. The fatigue strength shows anisotropy; the fatigue strength in the direction
parallel to the longitudinal axis of pores is higher than that in the perpendicular direction. Not only
anisotropic pores but also fiber texture grown along the pore direction contributes to the anisotropy in
the fatigue strength.
Room Temperature Superplastic Deformation of Closed-Cell Zinc Alloy Foams
Authors: Kitazono Koichi , Seo Teppei , Takiguchi Yoshihiro
Published: March 2009

Lightweight aluminum foams are attractive energy absorbing material for automotive
machines. Strength of aluminum foams manufactured through casting process is not so much high as
dense aluminum alloys due to difficult alloying. Ductility of aluminum foams manufactured through
powder metallurgical process is low due to fine oxide dispersions. In this paper, we introduce new
metallic foam having excellent energy absorbing property. Closed-cell Zn-22 mass%Al eutectoid
alloy foams are manufactured through powder metallurgical process. The Zn-22Al alloy is known as
typical superplastic material and shows superplastic deformation below 523 K, even at room
temperature. Using titanium hydride powder as a foaming agent, the porosity as high as 60% is
achieved. Solution treatment followed by quenching causes ductile compressive deformation at room
temperature. In addition, the absorbed energy of the Zn-22Al foams are much larger than those of
conventional aluminum foams.