Acta MaterialiaThis is an RSS file. You can use it to subscribe to this data in your favourite RSS reader, such as GoogleReader, or to display this data on your own website or blog. Subscribe to this data using MyMedWorm.Subscribe to this data using GoogleReader.Subscribe to this data using Bloglines.Subscribe to this data using MyYahoo.

This page shows you the latest items in this publication.

Pages: 1 2 3 4 5 6 7 8 9

421 records returned

2010 Acta Materialia, Inc. Gold Medal AwardEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
(Source: Acta Materialia)
Source: Acta Materialia - November 19, 2009 Category: Materials Science Source Type: journals

Editors for Acta MaterialiaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
(Source: Acta Materialia)
Source: Acta Materialia - November 19, 2009 Category: Materials Science Source Type: journals

Structural properties of materials created through freeze castingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Upon freezing of an aqueous suspension of colloidal particles, ice platelets or dendrites with high aspect ratios are formed that engulf or reject the particles, depending on their size and the velocity of the advancing ice front. As the particles are pushed between the growing crystals, concentrated regions of colloidal particles are formed. Recent experiments have exploited this to create strong, porous materials with a well-controlled microstructure. We investigate this process by means of molecular dynamics simulations, focusing on the effect of the ice front velocity on the structure of the resulting materia...
Source: Acta Materialia - October 23, 2009 Category: Materials Science Authors: Stephen A. Barr, Erik Luijten Source Type: journals

Mechanical anisotropy and deep drawing behaviour of AZ31 and ZE10 magnesium alloy sheetsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: The influence of the initial microstructure on the deep drawability and the associated microstructural evolution in two different magnesium alloy sheets, AZ31 and ZE10, has been examined. Tensile testing at room temperature shows that the AZ31 sheet has high plastic strain ratios, r=2–3, which are caused by strong basal-type texture. The ZE10 sheet shows lower r values, r∼1, as a result of its weak texture. Deep drawing experiments carried out over the temperature range 100–300°C revealed that the ZE10 sheet can be successfully deep-drawn at lower temperatures than the AZ31 sheet. The ZE10 cups show earing...
Source: Acta Materialia - October 15, 2009 Category: Materials Science Authors: Sangbong Yi, Jan Bohlen, Frank Heinemann, Dietmar Letzig Source Type: journals

Editors for Acta MaterialiaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
(Source: Acta Materialia)
Source: Acta Materialia - October 12, 2009 Category: Materials Science Source Type: journals

Load partitioning between single bulk grains in a two-phase duplex stainless steel during tensile loadingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: The lattice strain tensor evolution for single bulk grains of austenite and ferrite in a duplex stainless steel during tensile loading to 0.02 applied strain has been investigated using in situ high-energy X-ray measurements and finite-element modeling. Single-grain X-ray diffraction lattice strain data for the eight austenite and seven ferrite grains measured show a large variation of residual lattice strains, which evolves upon deformation to the point where some grains with comparable crystallographic orientations have lattice strains different by 1.5×10−3, corresponding to a stress of ∼300MPa. The finite...
Source: Acta Materialia - October 12, 2009 Category: Materials Science Authors: Peter Hedström, Tong-Seok Han, Ulrich Lienert, Jonathan Almer, Magnus Odén Source Type: journals

Preparation and formation mechanism of nanocomposites with fluorescent and magnetic propertiesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Fluorescent magnetic nanocomposites were successfully synthesized using the self-prepared Fe3O4 magnetic liquid and CdTe quantum dots (QDs) as precursors. High-resolution transmission electron microscopy, selected area electron diffraction, energy-dispersive spectroscopy and Fourier transform infrared spectroscopy were used to characterize the size, morphology, structure and composition of the nanocomposites. A fluorescent microscope was used to observe their micro-morphology. Magnetic and optical properties were characterized by a vibrating sample magnetometer and fluorescent spectrophotometer, respectively. The...
Source: Acta Materialia - October 12, 2009 Category: Materials Science Authors: H. Yan, J.C. Zhang, B.W. Yu, Y. Shen Source Type: journals

Optimization of the mechanical properties of virtual porous solids using a hybrid approachEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: A hybrid strategy based on artificial neural network/genetic algorithms is suggested to optimize the mechanical properties of cellular solids. Three-dimensional void structures are generated using a random sequential addition algorithm in which spherical void particles are positioned in a solid phase matrix with a control of their size distribution and overlapping. This allows us to create an open-cell structure with relative densities in the range 0.1–0.3. Finite element calculation is used to assess the effective Young’s modulus as a function of generation parameters. Relative Young’s moduli in the three ...
Source: Acta Materialia - October 12, 2009 Category: Materials Science Authors: Sofiane Guessasma, David Bassir Source Type: journals

Hydrogenography of MgyNi1−yHx gradient thin films: Interplay between the thermodynamics and kinetics of hydrogenationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: We monitor the hydrogenation of PTFE/Pd-capped MgyNi1−yHx gradient thin films using the change in optical transmission as a function of time, temperature and hydrogen pressure, to study the relation between kinetics and thermodynamics of hydrogenation of this multiphase hydride system. The interplay between kinetics and thermodynamics is used to extrapolate the hydrogenation equilibrium pressures via the H-absorption rate. Pressure–optical-transmission–isotherms determined independently at different temperatures provide a cross-check for the equilibrium pressure and the enthalpy of H-absorption. We find tha...
Source: Acta Materialia - October 12, 2009 Category: Materials Science Authors: R. Gremaud, C.P. Broedersz, A. Borgschulte, M.J. van Setten, H. Schreuders, M. Slaman, B. Dam, R. Griessen Source Type: journals

Effect of high-pressure torsion on hydrogen trapping in Fe–0.01mass% C and type 310S austenitic stainless steelEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: The effect of high-pressure torsion (HPT) on hydrogen trapping in Fe–0.01mass% C and type 310S stainless steel was studied by metallographic characterization and hydrogen measurement after hydrogen gas charging. Hardening of both materials after processing by HPT was achieved through grain refinement. Hydrogen trapping in the Fe–0.01mass% C was significantly increased by HPT processing, because of high binding energies of hydrogen with lattice defects such as dislocations and grain boundaries in body-centred cubic iron. In the type 310S processed by HPT, the hydrogen content that trapped by dislocations was l...
Source: Acta Materialia - October 12, 2009 Category: Materials Science Authors: Yoji Mine, Zenji Horita, Yukitaka Murakami Source Type: journals

First-principles assessment of hydrogen absorption into FeAl and Fe3Si: Towards prevention of steel embrittlementEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: We characterize the ability of two potential surface alloys, FeAl and Fe3Si, to prevent H incorporation into steel, with a view toward inhibiting steel embrittlement. Periodic density functional theory calculations within the generalized gradient approximation are used to evaluate H dissolution energetics and the kinetics of H diffusion into and through FeAl and Fe3Si. We predict increased dissolution endothermicities and diffusion barriers in both alloys compared to bulk Fe. Fe3Si is predicted to be the most effective at inhibiting H incorporation, with a 1.91eV [0.97eV] surface-to-subsurface diffusion barrier o...
Source: Acta Materialia - October 12, 2009 Category: Materials Science Authors: Donald F. Johnson, Emily A. Carter Source Type: journals

The geometry, topology and structure of amorphous solidsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Clusters of atoms can be divided into three categories depending on their topology. One of the categories provides the basis for development of a model of a perfectly random structure (ideal amorphous solid) using the non-equilateral triangle topology in the coordination shell. Metallic glasses solidify as amorphous solids with random arrangement of atoms. A model of Zr-based metallic glass has been constructed and described in terms of cluster topology, and compared with a recently published dynamic molecular model of the same alloy. It is shown that the pair distribution function for the ideal amorphous model r...
Source: Acta Materialia - October 12, 2009 Category: Materials Science Authors: Cheuk-Yu Lee, Zbigniew H. Stachurski, T. Richard Welberry Source Type: journals

Wettability of pure Ti by molten pure Mg dropletsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: The wetting behavior of molten pure Mg droplets on pure Ti substrate, a crucial phenomenon in the design of Mg matrix composites reinforced with Ti particles, was investigated by the sessile drop method. The contact angle was measured in high-purity argon (99.999%) at 1073K. In particular, the effects of two important parameters on the contact angle were evaluated: Mg evaporation during the wetting test; and surface oxide film of the substrate. The calculation method to estimate the modified contact angle involved taking the morphological changes of the droplet outline due to the evaporation into consideration. B...
Source: Acta Materialia - October 12, 2009 Category: Materials Science Authors: Katsuyoshi Kondoh, Masashi Kawakami, Hisashi Imai, Junko Umeda, Hidetoshi Fujii Source Type: journals

Kinetic effects in the mixed β to martensitic transformation in a Cu–Al–Ni shape memory alloyEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: A single crystal with a selected composition of a Cu–Al–Ni shape memory alloy, undergoing two martensitic phase transformations when cooling from the common parent phase, , has been studied by adiabatic calorimetry. As the coexistence of two different martensites has a strong influence on the transformation kinetics, both the forward and the reverse phase martensitic transformation have been carefully studied by means of very low thermal rate dynamic thermograms. Temperature memory effects have been observed in the transformation but not in the one. Finally, radiation-cooling procedures were used to study the...
Source: Acta Materialia - October 9, 2009 Category: Materials Science Authors: J. Rodríguez-Aseguinolaza, I. Ruiz-Larrea, M.L. Nó, A. López-Echarri, J. San Juan Source Type: journals

Orientation stress field analysis in polycrystalline bcc steel using neutron diffractionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We report here its application to characterize in situ the mechanical behaviour under uniaxial tension of a low alloyed 16MND5 bainitic steel used for nuclear reactor pressure vessels. It appears that the selected investigated phases exhibit very different mechanical responses. A large plastic deformation heterogeneity is observed. (Source: Acta Materialia)
Source: Acta Materialia - October 8, 2009 Category: Materials Science Authors: R. Dakhlaoui, V. Klosek, M.H. Mathon, B. Marini Source Type: journals

Colossal anelasticity in polycrystals deforming under conditions of diffusional creepEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Since diffusional creep viscosity depends strongly on the grain size, a variability in the grain size in a polycrystal can generate significant internal stresses. Upon unloading, the non-uniform internal stresses recover, leading to anelastic strains. The anelastic strains can be very large, approaching 100 times the elastic strains. We solve the case of bimodal viscosity in closed form to highlight the features of this type of anelasticity. The results are compared to the anelastic behavior of two-phase superplastic alloys. In such alloys the spatial variability in the diffusional viscosity can arise from the va...
Source: Acta Materialia - October 7, 2009 Category: Materials Science Authors: P. Lee, R. Raj Source Type: journals

Conversion of MX nitrides to Z-phase in a martensitic 12% Cr steelEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: A 12% Cr model steel was designed with the purpose of studying the nucleation and growth of modified Z-phase, Cr(V,Nb)N. The model alloy develops Z-phase after relatively short ageing times and contains only nitrides of Cr, V and Nb. Interferences from the presence of carbides and the development of Laves phase were avoided by keeping the C, W and Mo contents as low as possible. Transmission electron microscopy and X-ray diffraction analysis of extracted particles were used to follow the evolutions of phase composition, phase morphology and phase fraction, particularly of the precipitation of Z-phase, during agei...
Source: Acta Materialia - October 7, 2009 Category: Materials Science Authors: Leonardo Cipolla, Hilmar K. Danielsen, Dario Venditti, Paolo Emilio Di Nunzio, John Hald, Marcel A.J. Somers Source Type: journals

Micromechanics of high-temperature damage in dual-phase stainless steelEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: High-temperature ductility of dual-phase stainless steels is investigated using a micromechanics approach of damage and fracture. Two different microstructures are studied with either a lamellar or a globular morphology of the ferrite phase, the latter being twice as ductile as the former at 1150°C. The high-temperature damage evolution is characterized at different loading rates using notched round cylindrical bars producing different stress triaxialities, supplemented by fractographic analysis. The experimental observations have generated an advanced elasto-viscoplastic micromechanical damage model for both mi...
Source: Acta Materialia - October 7, 2009 Category: Materials Science Authors: B. Chéhab, Y. Bréchet, M. Véron, P.J. Jacques, G. Parry, J.-D. Mithieux, J.-C. Glez, T. Pardoen Source Type: journals

Sr- and Ti-site substitution, lattice dynamics, and octahedral tilt transition relationship in SrTiO3:Mn ceramicsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: SrTiO3:Mn ceramics, prepared according to the chemical formulae Sr1–xMnxTiO3 and SrTi1–yMnyO3, are studied by Fourier transform infrared and time-domain terahertz spectroscopy in the temperature range of 10–300K to support the incorporation of Mn ions into the perovskite lattice of SrTiO3, and to ascertain their different lattice site locations. The polar soft mode of the incipient ferroelectric SrTiO3 is found to be hardened in the whole temperature range by the substitution of Mn ions on Ti sites, and only in the low-temperature range by the Sr site substitution. Activation of the mode, associated with th...
Source: Acta Materialia - October 7, 2009 Category: Materials Science Authors: Alexander Tkach, Paula M. Vilarinho, Dmitry Nuzhnyy, Jan Petzelt Source Type: journals

Crystal structure, morphology and physical properties of LaCo1−xTixO3±δ perovskites prepared by a citric acid assisted soft chemistry synthesisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: The influence of the partial substitution of Co by Ti in the LaCoO3 perovskite system is studied by evaluating the electrical conductivity, the Seebeck coefficient and the thermal conductivity of the compounds up to T=1273K. The X-ray diffraction patterns of the LaCo1−xTixO3±δ (0.01⩽x⩽0.5) phases show two structural modifications depending on the Ti content. Compounds with x (Source: Acta Materialia)
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: Rosa Robert, Dmitry Logvinovich, Myriam H. Aguirre, Stefan G. Ebbinghaus, Laura Bocher, Petr Tomeš, Anke Weidenkaff Source Type: journals

A model for oxidation-assisted low cycle fatigue of superalloysEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Cracks in superalloys subject to an isothermal, sustained hold, compressive strain cycle experience cycle-by-cycle extension. The phenomenon has been attributed to the strains induced by the formation a thermally grown oxide (TGO) on the crack faces with the strain accommodated by alloy creep. Basic features have been elucidated through finite element calculations. The present objective is to develop a straightforward model that explicitly relates the fatigue to the TGO strains and the alloy creep rates. For this purpose, insights are first developed through finite element simulations. The results are rationalize...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: M.Y. He, A.G. Evans Source Type: journals

Thermal conductivity of semiconductor (bismuth–telluride)–semimetal (antimony) superlattice nanostructuresEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: In the present study, the thermal conductivity of superlattice bismuth–telluride (semiconductor)–antimony (semimetal) (Bi2Te3–Sb) nanostructures (nanowires and nanotubes) has been modeled using an incoherent particle model, approximating all the scattering to be diffuse and gray, and applying a Matthiessen-type simplification. The effect of varying the ratio of the superlattice nanowire segment lengths (L) of Sb and Bi2Te3 has also been studied assuming: (i) LSb=; (ii) LSb=0.25×; (iii) LSb=0.5×; (iv) LSb=2.0×; and (v) LSb=4.0×. It is shown that thermal conductivity of the superlattice nanowires reduces ...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: D. Pinisetty, R.V. Devireddy Source Type: journals

Single-step, rapid low-temperature synthesis of Si quantum dots embedded in an amorphous SiC matrix in high-density reactive plasmasEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: A simple, effective and innovative approach based on low-pressure, thermally nonequilibrium, high-density inductively coupled plasmas is proposed to rapidly synthesize Si quantum dots (QDs) embedded in an amorphous SiC (a-SiC) matrix at a low substrate temperature and without any commonly used hydrogen dilution. The experimental results clearly demonstrate that uniform crystalline Si QDs with a size of 3–4nm embedded in the silicon-rich (carbon content up to 10.7at.%) a-SiC matrix can be formed from the reactive mixture of silane and methane gases, with high growth rates of ∼1.27–2.34nms−1 and at a low su...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: Qijin Cheng, Shuyan Xu, Kostya (Ken) Ostrikov Source Type: journals

Orientation dependence of shock-induced twinning and substructures in a copper bicrystalEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Shock recovery experiments have been conducted to assess the role of shock stress and orientation dependence on substructure evolution and deformation twinning of a [100]/ copper bicrystal. Transmission electron microscopy of the post-shock specimens revealed that well-defined dislocation cell structures developed in both grains and the average cell size decreased with increasing shock pressure from 5 to 10GPa. Twinning occurred in the [100] grain, but not the grain, at the 10GPa shock pressure. The stress and orientation dependence of incipient twinning can be predicted by the stress and orientation conditions r...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: Fang Cao, Irene J. Beyerlein, Francis L. Addessio, Bulent H. Sencer, Carl P. Trujillo, Ellen K. Cerreta, George T. Gray III Source Type: journals

Effects of Ti, Zr, and Hf on the phase stability of Mo_ss+Mo3Si+Mo5SiB2 alloys at 1600°CEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Understanding the stability of the three-phase Mo_ss+Mo3Si+Mo5SiB2 region is important for alloy design of Mo–Si–B-based refractory metal intermetallic composites. In this work, thermodynamic modeling is coupled with guided experiments to study phase stability in this three-phase region of the Mo–Si–B–X (X=Ti, Zr, Hf) system. Both the calculated and experimental results show that additions of Zr and Hf limit significantly the stability of the three-phase region because of the formation of the ternary phases MoSiZr and MoSiHf, while Ti addition leads to a much larger region of stability for the three-pha...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: Ying Yang, H. Bei, Shuanglin Chen, E.P. George, Jaimie Tiley, Y. Austin Chang Source Type: journals

Kinetic stages in the crystallization of deeply undercooled body-centered-cubic and face-centered-cubic metalsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Crystallization velocities in several face-centered-cubic (fcc) and body-centered-cubic (bcc) metals are calculated using molecular dynamics computer simulations for the (100) and densely packed (111) or (110) planar interfaces. We show that the crystallization kinetics can be divided into high- and low-temperature regimes, separated at a crossover temperature, Tc, which is associated with kinetic arrest. In the high-temperature regime, the velocity in both fcc and bcc metals initially increases with the degree of undercooling before reaching a maximum somewhat above the glass temperature. The kinetics is charact...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: Y. Ashkenazy, R.S. Averback Source Type: journals

Lattice dynamical finite-element methodEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: A lattice dynamical finite-element method (LDFEM) is proposed for multiscale analysis of stressed complex crystals. Interatomic potential is embedded into the constitutive relation within the hyperelasticity framework, and two energy-based lattice instability criteria, the Λ criterion and the soft phonon criterion, are incorporated into LDFEM for capturing stress-driven instabilities in a perfect crystal. The simulations of uniaxial loadings and a two-dimensional nanoindentation of B2-NiAl are performed using both LDFEM and molecular dynamics (MD). The good agreement of the simulated mechanical responses between...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: Xiaohui Liu, Jianfeng Gu, Yao Shen, Ju Li, Changfeng Chen Source Type: journals

Direct observation of the NiTi martensitic phase transformation in nanoscale volumesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We report on quantitative in situ transmission electron microscopy nanocompression tests used to study the deformation behavior of NiTi pillars on the nanometer scale. By recording the diffraction patterns in real time we have obtained direct evidence that the stress-induced B2 to B19′ (austenite to martensite) transformation exists in NiTi even when the sample size is below 200nm. Correlation of the appearance of the B19′ phase in the diffraction pattern with our quantitative data showed that the transformation starts at approximately 1GPa. We found that the transformation occurred through a multi-step process, and th...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: Jia Ye, Raja K. Mishra, Alan R. Pelton, Andrew M. Minor Source Type: journals

Temperature and structural dependence of electrochemical activity and fuel cell performanceEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: The dependence on temperature and structure of the electrochemical activity of a catalyst supported on hollow carbon nanocages (HCNCs) with large scales (>5gh–1) by a simple N2-bubbling floating method is discussed. The effect of gas flow on an HCNC-supported catalyst was systematically studied in our previous work. Here we specify the electrocatalytic activity of the samples with different temperatures and graphite structures under 900 and 1000°C by cyclic voltammograms. The peak current density of H2-adsorption/desorption is four times higher than that of the commercial Pt/C (Vulcan XC-72). Besides the compa...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: Jun Jie Niu, Jian Nong Wang Source Type: journals

Grain boundary self-diffusion in polycrystalline nickel of different purity levelsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Grain boundary self-diffusion in Ni materials of two different purity levels (99.6 and 99.999wt.%) was measured over wide temperature intervals using the radiotracer technique and applying the 63Ni radioisotope. The diffusion experiments were performed in both Harrison’s type B and type C kinetic regimes. The diffusional grain boundary width, δ, was found to be equal to 0.54±0.1nm, that is reasonably close to the accepted value of in face-centred cubic metals. The purer the material, the higher the grain boundary diffusivity and the lower the corresponding activation enthalpy of self-diffusion along general h...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: Sergiy V. Divinski, Gerrit Reglitz, Gerhard Wilde Source Type: journals

Atomistic simulations of void migration under thermal gradient in UO2Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: It is well known that within a few hours after startup of a nuclear reactor, the temperature gradient within a fuel element causes migration of voids/bubbles radially inwards to form a central hole. To understand the atomic processes that control this migration of voids, we performed molecular dynamics (MD) simulations on single crystal UO2 with voids of diameter 2.2nm. An external temperature gradient was applied across the simulation cell. At the end of the simulation run, it was observed that the voids had moved towards the hot end of the simulation cell. The void migration velocity obtained from the simulatio...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: Tapan G. Desai, Paul Millett, Michael Tonks, Dieter Wolf Source Type: journals

Simulation of stress concentration in Mg alloys using the crystal plasticity finite element methodEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: A crystal plasticity finite element method (CPFEM), considering both crystallographic slip and deformation twinning, was developed to simulate the spatial stress concentration in AZ31 Mg alloys during in-plane compression. A predominant twin reorientation (PTR) model was successfully implemented to capture grain reorientation due to deformation twinning in twin-dominated deformation. By using the direct mapping technique for electron backscatter diffraction (EBSD) data, CPFEM can capture the heterogeneity of stress concentration at the grain boundaries in AZ31 Mg alloys during in-plane compression. The model demo...
Source: Acta Materialia - October 5, 2009 Category: Materials Science Authors: S.-H. Choi, D.H. Kim, S.S. Park, B.S. You Source Type: journals

First-principles study of solute–vacancy binding in magnesiumEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Solute–vacancy binding is a key quantity in understanding diffusion kinetics, and may also have a considerable impact on the hardening response in Mg alloys. However, the binding energetics between solute impurities and vacancies in Mg are notoriously difficult to measure accurately and are largely unknown. Here, we present a large database of solute–vacancy binding energies in Mg from first-principles calculations based on density functional theory. Our vacancy formation energy and dilute mixing energy, which are byproducts of the solute–vacancy binding calculations, show good agreement with experiments, w...
Source: Acta Materialia - September 30, 2009 Category: Materials Science Authors: Dongwon Shin, Christopher Wolverton Source Type: journals

Editors for Acta MaterialiaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
(Source: Acta Materialia)
Source: Acta Materialia - September 28, 2009 Category: Materials Science Source Type: journals

Relationships between rolled grain shape, deformation bands, microstructures and recrystallization textures in Al–5%MgEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study, the textures and microstructures of Al–5%Mg after cold rolling 95% and recrystallization at 300 and 450°C have been investigated. The cold rolling textures were typical but the recrystallization textures at 300°C comprised Cube and S and at 450°C, Cube, ND Rotated Cube plus a weak Q component. The deformed grains were wavy in the longitudinal section as a result of composite-like behaviour, and the narrowed regions had scattered orientations which weakened the final annealing texture. Another feature was grains dividing into their respective crystallographic complements. S grains frequently behaved in t...
Source: Acta Materialia - September 28, 2009 Category: Materials Science Authors: C.S.T. Chang, B.J. Duggan Source Type: journals

Characterization of planar features in Mg–Y–Zn alloysEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: The planar features in a Mg–8Y–2Zn–0.6Zr (wt.%) alloy solution-treated at 500°C for 1h have been examined using conventional transmission electron microscopy and atomic-resolution high-angle annular dark-field scanning transmission electron microscopy. Three types of planar features are detected in the microstructure. The first type, which was previously reported to be an intrinsic stacking fault I1 bounded by a Frank partial dislocation, is shown to be the 14H precipitate phase that is associated with Shockley partial dislocations. The second type is also a precipitate phase that has a single unit cell he...
Source: Acta Materialia - September 28, 2009 Category: Materials Science Authors: Y.M. Zhu, A.J. Morton, M. Weyland, J.F. Nie Source Type: journals

Pulsed laser deposition-induced reduction of SrTiO3 crystalsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We report a generic method for fast and efficient reduction of strontium titanate (SrTiO3, STO) single crystals by pulsed laser deposition (PLD) of thin-films. The reduction was largely independent of the thin-film material deposited on the crystals. It is shown that thermodynamic conditions (450°C, 10−7 torr, 10–60min), which normally reduce STO (001) substrates to roughly 5nm into a crystal substrate, can reduce the same crystals throughout their 500μm thickness when coupled with the PLD. In situ characterization of the STO substrate resistance during thin-film growth is presented. This process opens up the possibi...
Source: Acta Materialia - September 28, 2009 Category: Materials Science Authors: Matthew L. Scullin, Jayakanth Ravichandran, Choongho Yu, Mark Huijben, Jan Seidel, Arun Majumdar, R. Ramesh Source Type: journals

Liquid structure as a guide for phase stability in the solid state: Discovery of a stable compound in the Au–Si alloy systemEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: A new crystalline ground state was discovered in the Au–Si system through first-principles electronic structure calculations. The new structure was found using the experimentally and theoretically determined local atomic structure in the liquid as a guide for the solid state. Local atomic structure in the liquid was matched with that for all known crystal structures as compiled in the Pauling File structural database. The best matching crystalline structures were then explicitly calculated using first-principles methods. Most candidate crystal structures were found to be close, but above the enthalpy of a compo...
Source: Acta Materialia - September 28, 2009 Category: Materials Science Authors: Emre S. Tasci, Marcel H.F. Sluiter, Alain Pasturel, Pierre Villars Source Type: journals

Stronger silicon for microsystemsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Few studies have deliberately varied the microstructure of microfabricated polycrystalline silicon (polySi) to examine their effects on resulting mechanical performance and reliability. In the present study, the tensile strength distributions of four microfabricated polySi variants were examined, corresponding to two different grain sizes (285nm vs. 125nm) in both the undoped and heavily P-doped conditions. Microtensile tests revealed that the coarse-grained materials exhibited significantly lower characteristic strengths (1.48–1.76GPa) compared to the fine-grained material (2.80–2.83GPa). The difference in s...
Source: Acta Materialia - September 28, 2009 Category: Materials Science Authors: B.L. Boyce, M.J. Shaw, P. Lu, M.T. Dugger Source Type: journals

Thermodynamic and experimental study on phase stability in nanocrystalline alloysEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Nanocrystalline alloys exhibit apparently different phase transformation characteristics in comparison to the conventional polycrystalline alloys. The special phase stability and phase transformation behavior, as well as the essential mechanisms of the nanocrystalline alloys, were described quantitatively in a nanothermodynamic point of view. By introducing the relationship between the excess volume at the grain boundary and the nanograin size, the Gibbs free energy was determined distinctly as a function of temperature and the nanograin size. Accordingly, the grain-size-dependence of the phase stability and phas...
Source: Acta Materialia - September 28, 2009 Category: Materials Science Authors: Wenwu Xu, Xiaoyan Song, Nianduan Lu, Chuan Huang Source Type: journals

Point defects in multicomponent ordered alloys: Methodological issues and working equationsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: The aim of this work is to give the independent-point-defect thermodynamics of ordered compounds a sufficiently general flavour, adapted to and working for multicomponent alloys. Generalizing previous approaches, we first show that an appropriate description for a crystal with point defects allows treatment of the practically important pressure and defect volume parameters in the grand canonical framework, the equivalence of which is explicited with the closer to experiments isothermal–isobaric conditions. Since industrial applications often involve multialloyed compounds, we then derive an operational tool for...
Source: Acta Materialia - September 28, 2009 Category: Materials Science Authors: Rémy Besson Source Type: journals

Structural and optical properties of encapsulated ZnO in porous host matrixEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: ZnO nanoparticles were encapsulated in the porous activated carbon matrix by incipient-wetness impregnation. The use of the small host matrix allowed the size confinement of ZnO by utilizing the porous nature of the host matrix. Partial fixation of ZnO in the porous matrix determines the size and the dispersion of the particles. Experiments at different calcination temperatures were carried out to investigate structural and optical properties of ZnO nanoparticles in the porous activated carbon matrix using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and photoluminescence. The optimal calci...
Source: Acta Materialia - September 28, 2009 Category: Materials Science Authors: Noppadon Sathitsuksanoh, Dake Wang, HongYun Yang, Yong Lu, Minseo Park Source Type: journals

Effect of total dopant concentration and dopant ratio on conductivity of (DyO1.5)x–(WO3)y–(BiO1.5)1−x−yEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Dysprosium- and tungsten-stabilized bismuth oxide (DWSB) electrolytes were developed to achieve higher conductivity. With double doping, stabilization of the cubic phase was achieved with as little as 12mol.% total dopant concentration, resulting in higher conductivity. The conductivity of DWSB electrolytes increased linearly as the total dopant concentrations decreased with fixed dopant ratio. Overall, DWSB has a closer inherent structure to pure δ-Bi2O3 than any singly doped compositions. Both lattice parameter and conductivity linearly extrapolate with total dopant concentration to that of pure δ-Bi2O3, resu...
Source: Acta Materialia - September 28, 2009 Category: Materials Science Authors: Doh Won Jung, Keith L. Duncan, Eric D. Wachsman Source Type: journals

A three-dimensional sharp interface model for the quantitative simulation of solutal dendritic growthEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: A three-dimensional (3-D) sharp interface model is developed to simulate the solutal dendritic growth in the low Péclet number regime. The model adopts a previously proposed solutal equilibrium approach to calculate the evolution of the solid/liquid interface. To describe specific crystallographic orientations of 3-D dendritic growth, a weighted mean curvature algorithm incorporated with the anisotropy of surface energy is proposed, allowing the simulation of 3-D dendrites with various orientations in a straightforward manner. The model validation is performed by comparing the simulations with the analytical pre...
Source: Acta Materialia - September 28, 2009 Category: Materials Science Authors: Shiyan Pan, Mingfang Zhu Source Type: journals

Modeling size effects on fracture toughness by dislocation dynamicsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: The effects of grain size and of crack-tip blunting radius on the fracture toughness of tungsten polycrystals are studied by using a combined dislocation dynamics/cohesive zone model (CZM). Two-dimensional dislocation dynamics are employed to analyze crack-tip plasticity and crack propagation is characterized by a CZM. The geometry of the crack and the corresponding boundary conditions are described by means of a boundary element method with dislocation dipoles as fundamental solution. Grain boundaries are introduced as obstacles for dislocation motion. Numerical experiments reveal that the fracture toughness dec...
Source: Acta Materialia - September 28, 2009 Category: Materials Science Authors: X.H. Zeng, A. Hartmaier Source Type: journals

Structural rejuvenation in a bulk metallic glass induced by severe plastic deformationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Using high-energy X-ray diffraction we examined the atomic structure in bulk metallic glass samples which underwent severe plastic deformation by the high-pressure torsion (HPT) technique. We obtained the atomic pair distribution function (PDF) and determined the changes in the PDFs due to deformation. The observed changes in the PDF clearly show structural disordering, which suggests structural rejuvenation by heavy deformation. However, the changes cannot be explained simply in terms of creating excess free volume, and they indicate that much more extensive atomic rearrangements take place as a consequence of d...
Source: Acta Materialia - September 27, 2009 Category: Materials Science Authors: W. Dmowski, Y. Yokoyama, A. Chuang, Y. Ren, M. Umemoto, K. Tsuchiya, A. Inoue, T. Egami Source Type: journals

Iron–chromium alloy nanoparticles produced by pulsed sonoelectrochemistry: Synthesis and characterizationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study describes synthesis of Fe–Cr alloy nanoparticles by using a method which couples electrodeposition of metals with the employment of high power ultrasound. The production of alloyed nanoparticles was performed using a 20kHz titanium alloy horn ultrasound generator, a “sonoelectrode” generating short current pulses (tON) triggered and followed immediately by ultrasonic pulses (tUS). A rest time (tr) restores the initial conditions close to the sonoelectrode. The final product is a suspension of nanoparticles with high purity and high surface/volume ratio, which could be controlled by varying process paramete...
Source: Acta Materialia - September 27, 2009 Category: Materials Science Authors: Valentina Zin, Manuele Dabalà Source Type: journals

Effects of boron on the microstructure and thermal stability of directionally solidified NiAl–Mo eutecticEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Abstract: Microalloying with 0.01at.% B decreases the range of growth speeds over which a well-aligned fibrous eutectic microstructure can be obtained in directionally solidified NiAl–Mo. Compared to the undoped alloy, the size/spacing of the Mo fibers is larger, and the fiber density smaller, in the B-doped alloy. Annealing at 1400°C coarsens the fibers by a mechanism involving fault migration and annihilation driven by diffusion along the fiber–matrix interface. The coarsening kinetics, given by the decrease in Mo fiber density with time, is exponential, and microalloying with B decreases the coarsening rate. (Source: Acta Materialia)
Source: Acta Materialia - September 25, 2009 Category: Materials Science Authors: A. Gali, H. Bei, E.P. George Source Type: journals