bluuebunny/crossref_metadata_2025_split huggingface dataset:
Substitution Behavior of Ni3X-type Compounds with D0a Structure
Authors: Sugimura H. , Kaneno Y. , Takasugi T. 
Published: April 2011

ABSTRACTThe site preference of ternary additions in GCP (geometrically close-packed) Ni3X-type compounds with D0a structure was determined from the direction of the single-phase region of the D0a phase in the reported ternary phase diagrams. The thermodynamic model based on the Bragg-Williams approximation, which is based on the change in heat of formation of the host compound by a small addition of ternary solute, was applied to predict the site preference of ternary additions. The heat of formation used in the thermodynamic calculation was derived from Miedema’s formula. Good agreement was obtained between the thermodynamic model and the result of the literature search.
Evaluation of Solubility Limit of Carbon in Ni3AlC1-x
Authors: Hosoda Hideki , Inamura Tomonari 
Published: April 2011

ABSTRACTIn order to clarify the phase stability of E21-type intermetallic carbides, the maximum solid solubility of carbon in Ni3AlC1-x was evaluated by taking into account the strain energy and the chemical energy for the formation of the Ni6C cluster (EM6C). It was found that the maximum carbon content calculated was 0 at.%C at EM6C≥0, 3.5 at.%C at EM6C = -5 kJ/mol, 6.5 at.%C at EM6C = -10 kJ/mol, 10 at.%C at EM6C = -15 kJ/mol and 13 at.%C at EM6C = -20 kJ/mol, respectively. Experimentally determined maximum carbon contents in Ni3Al in the literature can be explained when EM6C is ranged from -5 to -15 kJ/mol, and the solid solubility is found to be sensitive to EM6C. The attractive interaction between Ni and C seems to be due to covalent bonding. Similar attractive chemical interaction between transition metals and carbon must stabilize E21 phases.
Crystallographic Characteristics of Shape Memory Alloys
Authors: Krishnan Madangopal 
Published: April 2011

ABSTRACTThe martensitic microstructure of shape memory alloys is an aggregate of self accommodating plate groups. The principal character of this aggregate is its demonstration of pseudoplasticity, wherein a macroscopic shape change is brought about by extensive rearrangement and reorientation of the self accommodating martensite variants, and that of microstructural reversibility, wherein the polyvariant microstructure transforms back to the original grain of the parent phase after pseudoplastic deformation. These aspects of the shape memory intermetallic alloys are intriguing and, to a great extent, unsolved. The aim of this paper is to show that the underlying crystallographic interrelationships of the self accommodating microstructure of intermetallic alloys are responsible for the observed effect. The paper will discuss the relation between autocatalytic nucleation and self accommodation, the relation between microstructural reversibility and intervariant interfaces of the martensitic microstructure and the manifestations of microstructural irreversibility using results from the microstructural examination of the self accommodating microstructures.
Structure Analysis of a Long Period Stacking Ordered Phase in Mg-Al-Gd Alloys
Authors: Yokobayashi Hideyuki , Kishida Kyosuke , Inui Haruyuki , Yamasaki Michiaki , Kawamura Yoshihito 
Published: April 2011

ABSTRACTCrystal structure of a long period stacking ordered (LPSO) phase newly found in Mg-Al-Gd ternary alloys was investigated by scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM). The Mg-Al-Gd LPSO phase was confirmed to be constructed with 6-layer structural blocks, which is similar to the case of the 18R-type LPSO phases in the other Mg-TM-RE alloys. Atomic resolution high-angle annular dark-field (HAADF) STEM imaging revealed that Gd atoms are enriched in four layers instead of two layers and are ordered in a long range within the 6-layer structural block.
Experimental Studies of Bonding Related Properties in Binary Intermetallics by Convergent Beam Electron Diffraction
Authors: Sang X. H. , Kulovits A. , Wiezorek J. 
Published: April 2011

ABSTRACTAccurate Debye-Waller (DW) factors of chemically ordered β-NiAl (B2, cP2, ${\rm{Pm}}\bar 3 {\rm{m}}$) have been measured at different temperatures using an off-zone axis multi-beam convergent beam electron diffraction (CBED) method. We determined a cross over temperature below which the DW factor of Ni becomes smaller than that of Al of ~90K. Additionally, we measured for the first time DW factors and structure factors of chemically ordered γ1-FePd (L10, tP2, P4/mmm) at 120K. We were able to simultaneously determine all four anisotropic DW factors and several low order structure factors using different special off-zone axis multi-beam convergent beam electron diffraction patterns with high precision and accuracy. An electron charge density deformation map was constructed from measured X-ray diffraction structure factors for γ1-FePd.
Microstructure Analysis of The Channel Regions in Dual Two-phase Intermetallic Alloy Based on The Ni3Al-Ni3V Pseudo-binary Alloy System
Authors: Moronaga T. , Kaneno Y. , Tsuda H. , Takasugi T. 
Published: April 2011

ABSTRACTDual two-phase intermetallic alloys based on the Ni3Al-Ni3V pseudo-binary alloy system have been reported to display high phase and microstructure stabilities and good mechanical properties at high temperature and are therefore considered to be used as a next generation type of high temperature structural materials. The microstructure of the dual two-phase intermetallic alloys is composed of primary Ni3Al and the channel (eutectoid) regions consisting of Ni3Al+Ni3V. In this study, the microstructure of the channel regions was investigated by a transmission electron microscope (TEM). The contrasts of the channel regions showed a complicated microstructure in bright-field images. However, the electron beam diffraction consisted of a single set of patterns and the spots did not accompany streaks, indicating that crystallographic coherency among the constituent phases or the domains is very high. It was also shown that the lattice misfit between the a-axis of Ni3Al and the c-axis of Ni3V is larger than that between the a-axis of Ni3Al and the a-axis of Ni3V. From the dark-field observation, it was found that the c-axis of Ni3V domains in the channel regions is oriented perpendicular to the interface between primary Ni3Al and Ni3V. Therefore, it is suggested that the crystallographic orientation of Ni3V in the channel regions is aligned in the manner of lowering an internal stress caused by the lattice misfit between primary Ni3Al precipitates and Ni3V domains.
Density Functional Theory Calculations On Magnetic Properties Of Actinide Compounds
Authors: Heifets Eugene , Gryaznov Denis 
Published: April 2011

ABSTRACTWe have performed a detailed analysis of the magnetic (collinear and noncollinear) order and atomic and electron structures of UO2, PuO2 and UN on the basis of density functional theory with the Hubbard electron correlation correction (DFT+U). We have shown that the 3-k magnetic structure of UO2 is stabilized for the Hubbard parameter value of U=4.6 eV (while J=0.5 eV) when Dudarev’s formalism is used. UO2 keeps cubic shape in this structure. Two O atoms nearest to each U atom in direction of its magnetic moment move toward this U atom. Neither UN nor PuO2 shows the energetical preference for the rhombohedral distortion, in contrast to UO2, and, thus, no complex 3-k magnetic structure in these materials. Both materials have the AFM tetragonal <001> structure at reasonable choice of parameters U and J.
Damage generated by MeV-ion Beams on Titanium Surface in Oxidizing Environment
Authors: Do Ngoc-Long , Bérerd Nicolas , Moncoffre Nathalie , Gorse-Pomonti Dominique 
Published: April 2011

ABSTRACTThe study of the irradiation effects on titanium surfaces in oxidizing environment using multi-charged Argon ions in the MeV range shed into light the following points:-Significant oxide film thickening for the film grown at 500°C under irradiation at 4 and 9 MeV, by comparison with the TiO2 rutile film grown under same environmental conditions without irradiation;-Formation of large round –shaped craters, of diameter approaching 200 nanometers, at the titanium surface under irradiation at 500°C provided that the environment is enough oxidizing or provided that the metal surface is covered by a sufficiently thick oxide film.Practically, and for the present system, the superficial craterization is observed if the thickness of the superficial oxide is equal to twice that of the native oxide (~3 nm).
Tunneling Currents in Nanoscale high-κ MOS Structures
Authors: Vercik Andrés 
Published: April 2011

ABSTRACTFurther improvements of integrated circuits depend on the continuous downscaling of MOSFET´s, well beyond the limits for which direct tunneling currents are acceptable. These leakage currents affect both the stand-by power dissipation and the formation of the inversion layer ate the semiconductor surface, i.e., the channel formation. The most promising strategy to overcome this problem is the use of high-κ insulator in substitution of or as an additional layer on the traditional silicon dioxide. The aim of this work is using a recently developed theory to describe tunneling from inversion layers for high-κ insulators or stacks and analyze the effects of tunneling current on the thermal equilibrium in these cases.
SANS Study of Carbon Addition in Ti–45Al–5Nb
Authors: Staron P. , Schimansky F.-P. , Scheu C. , Clemens H. 
Published: April 2011

ABSTRACTThe distribution of carbon in Ti–45Al–5Nb–0.5C was studied using small-angle neutron scattering (SANS). In an earlier study, carbon had been found to form small perovskite precipitates in a γ-TiAl alloy without Nb, which significantly increase the strength of the material. In the Nb-containing alloy, however, no strengthening precipitates were observed, but most of the C was found to be homogeneously distributed. Atom probe investigations revealed only few C-enriched regions. The present SANS investigation was carried out to confirm the presence and size distribution of these C-enriched regions in the material. The SANS results show that a small volume fraction of such C-enriched regions is present, while the large number of small precipitates found in the alloy without Nb is indeed missing in the Nb-containing alloy.
Effect of The Refractory Element Additions on Microstructure and Mechanical Property of Two-phase Intermetallic Alloys Based on The Ni3Al-Ni3V Pseudo-binary Alloy System
Authors: Moronaga T. , Ishii S. , Kaneno Y. , Tsuda H. , Takasugi T. 
Published: April 2011

ABSTRACTTwo-phase intermetallic alloys composed of geometrically close packed (GCP) Ni3Al (L12 phase) and Ni3V (D022 phase) have attractive mechanical properties at high temperature, and are therefore considered to be used as high temperature structural materials. In this study, the effect of Ta and Re addition on the microstructure and hardness of two-phase intermetallic alloys was investigated. The addition of Ta remarkably enhanced the hardness due to solid solution hardening of the constituent phases. On the other hand, the addition of Re retarded the formation of the two-phase microstructure, resulting in the lowest hardness in the solution treated condition. By aging at 1223 K, the Ni solid solution in the Re added alloy decomposed to Ni3Al and Ni3V, accompanied by precipitates of a Re-rich phase. Consequently, the hardness rapidly increased with increasing aging time. Simultaneous addition of Ta and Re induced very fine precipitates of a Re-rich phase after aging, and consequently resulted in a higher hardness than by the addition of Ta or Re alone.
Phase-Field Simulation of Antiphase Boundary Migration in Intermetallic Compounds with Solute and Vacancy Segregation
Authors: Koizumi Yuichiro , Yokoi Tatsuya , Ouchi Masayuki , Minamino Yoritoshi , Yoshiya Masato , Allen Samuel M. 
Published: April 2011

ABSTRACTThe effects of solute and vacancy segregation on APB migration in Ti3Al, and their dependence on composition, have been investigated by using a phase-field simulation in which vacancy distribution is taken into account. Al-atoms are depleted and vacancies segregate at APB in stoichiometric Ti3Al (Ti-25Al), whereas Al-atoms segregate and vacancies are depleted in Alrich one (Ti-28Al). The simulation indicates that APB in Ti3Al migrates much faster in Ti-25Al than in Ti-28Al with the effect of vacancy segregation whereas it migrates slightly faster in Ti-28Al than in Ti-25Al in the absence of the effect of vacancy segregation.
Microstructural Studies of Multiphase (Zr,Ti)(V,Cr,Mn,Co,Ni)2 Alloys for NiMH Negative Electrodes
Authors: Bendersky L. A. , Wang K. , Boettinger W. J. , Newbury D. E. , Young K. , Chao B. 
Published: April 2011

ABSTRACTThe solidification microstructures of six Laves-based (Zr,Ti)(TM,Ni)2 alloys (TM= V,Cr, Mn,Co) intended for use as novel negative electrodes in Ni-metal hydride batteries were studied here; these alloys often have their best electrochemical properties when in the cast state. Solidification occurs by dendritic growth of a hexagonal C14 Laves phase followed by peritectic solidification of a cubic C15 Laves phase and formation of a cubic B2 phase in interdendritic regions. The observed sequence of Laves phase C14/C15 upon solidification agrees with predictions using effective compositions and thermodynamic assessments of the ternary systems, Ni-Cr-Zr and Cr-Ti-Zr. The paper also examines the complex internal structure of the interdendritic grains formed by solid-state transformation, which plays an important role in the electrochemical charge/discharge characteristics. By studying one alloy it is shown that the interdendritic grains solidify as a B2 (Ti,Zr)44(Ni,TM)56 phase, and then undergo transformation to Zr7Ni10-type, Zr9Ni11-type and martensitic phases. The transformations obey orientation relationships between the high-temperature B2 phase and the low-temperature Zr-Ni-type intermetallics, and consequently lead to a multivariant structure. Binary Ni-Zr and ternary Ti-Ni-Zr phase diagrams were used to rationalize the formation of the observed domain structure.
The Role of Si and Sb in the Si-Sb-Te Phase-change Material
Authors: Wu Liangcai , Zhou Xilin , Song Zhitang , Ni Henan , Rao Feng , Ren Kun , Peng Cheng , Song Sannian , Zhang Ting , Liu Bo , Feng Songlin , Chen Bomy 
Published: April 2011

ABSTRACTSb-rich Si-Sb-Te phase change materials with different Si contents were proposed and fabricated, and the role of Si and Sb in the Si-Sb-Te alloys was discussed. The resistance-temperature and retention properties of the Sb-rich Si-Sb-Te alloys were studied. Devices based on the Sb-rich Si-Sb-Te alloys were fabricated by a 0.18 μm CMOS technology and device properties were studied by pulsed mode resistance-voltage (R-V) measurements. Experimental results show that the crystallization temperature and data retention ability of the Sb-rich Si-Sb-Te alloys were obviously improved with increasing Si content, but the electrical properties degenerate if too much Si was added. Sb is helpful to promote the crystallization process, but excessive Sb decreases the thermal stability. So, in order to obtain practicable Sb-rich Si-Sb-Te phase change materials, suitable Si and Sb contents are required to balance the device performances between electrical switching property and thermal stability or data retention ability.
Interphase Energies and Nonequilibrium Growth of γ-precipitates in Al-Ag: A DFT Study
Authors: Watts D. J. , Johnson D. D. , Finkenstadt Daniel 
Published: April 2011

AbstractDensity-functional theory (DFT) calculations of interphase boundary energies provide useful input for many precipitate growth models in alloy systems [1]. One example is Al-Ag, where a rich variety of precipitate types exist, and the sizes and shapes are determined roughly by a Wulff construction, namely, minimizing surface free energies with respect to geometry. This is only a first approximation, however, as kinetic-considerations and crystallography do not allow for a uniform, isotropic growth. Consequently, a nonequilibrium growth model is developed for γ-plates [2], which attempts to connect semi-coherent (ledge) and incoherent (edge) interface growth rates in a way that incorporates shape and interface energies. Through this connection, we make a DFT model with approximate unit cells that mirror experimental conditions, which gives accurate predictions for precipitate aspect ratios and time-development of nonequilibrium shapes. Starting from an explicit calculation of Suzuki segregation of solute to stacking-faults, we find a mechanism for nucleation of nanoscale γ-plates on quenched defects, identify a bulk structure from a calculated phase diagram that gives the relevant HCP equilibrium precipitate structure occurring at 50 at.% Ag and calculate critical nucleation parameters for γ-precipitate formation. Applications to island-coarsening and lath morphology are also discussed.
Characterization of 14YWT As-Atomized, Milled, Milled and Annealed Powders and HIP Consolidated Alloys
Authors: Cunningham Nicholas J. , Etienne Auriane , Odette G. Robert , Stergar Erich , Wu Yuan , Wirth Brian D. 
Published: April 2011

ABSTRACTNanostructured ferritic alloys (NFA) are Fe-Cr based ferritic stainless steels containing an ultrahigh density of very stable Y-Ti-O nanofeatures (NFs) that provide dispersion strengthening and radiation damage resistance for candidate Generation IV and future fusion reactor materials. This work is a small and focused part of a larger collaboration to produce large best practice NFA heats. The powders analyzed were rapidly solidified from a melt containing Fe-14%Cr, 3%W, 0.4%Ti and 0.2%Y by gas atomization in Ar, Ar/O, and He atmospheres. Note this represents a different processing path from conventional NFA production where metallic powders are mechanically alloyed with Y2O3 by ball milling. Electron probe microanalysis (EPMA), atom probe tomography (APT), transmission electron microscopy (TEM) and small angle neutron scattering (SANS) were used to characterize the powders in the as-atomized, ball milled and ball milled and annealed conditions. EPMA showed the Y is heterogeneously distributed and phase separated in all the as atomized powders, but attritor milling for 20 to 40 h is required to mix the Y. Milling also creates a significant quantity of O as well as N contamination. Subsequent powder annealing treatments, typically at 1150°C, result in the precipitation of a high density of NFs. All the annealed powder variants show a bimodal grain size distribution, but TEM and APT show NFs in both large and small grains. Reducing O content added during milling of the Ar atomized powders increased the precipitate size and decreased the number density, adversely affecting the hardness.
Study of Ion Beam Mixing by x ray reflectometry
Authors: Simeone D , Gosset D , Luneville L. , Baldinozzi G , Moncoffre N , Deranlot C. 
Published: April 2011

ABSTRACTWe present in this text a new experimental tool to study the mixing of atoms under irradiation. Based on physics of x ray diffraction, the specular reflectivy of x ray was used to estimate the Auto Correlation Function associated with the electron density gradient. The accuracy of the ACF is around 1 nanometer and does not evolve with the thickness of the probed layer. Thus, this point allows accurately measuring the broadening of the electron density gradient spreading induced by irradiation. Such an accurate profile extracted over a large range of fluences (about 3 decades) would lead to the determination of the functional dependence of this spreading with the fluence. This could allow pointing out the main mechanisms triggering the atomic mixing over large distances when atomic mixing occurring in thermal spikes is washed out.
Phase Equilibria in the Nb-rich Nb-Ti-Si-Cr-Hf alloys
Authors: Yang Ying , Bewlay Bernard P. , Chang Austin 
Published: April 2011

ABSTRACTRefractory Metal-Intermetallic Composites (RMICs) based on the Nb-Si system have been considered as candidates for the next-generation high temperature materials (i.e. >1200°C). Ti, Cr and Hf have been shown to have beneficial effects on the oxidation resistance and mechanical properties of Nb-Si alloys. The present study has determined phase equilibria in the Nb-rich region of the Nb-Si-Ti-Cr-Hf system via the Calphad approach. The alloying effects of Cr and Hf on the microstructure of Nb-Si-Ti alloys are understood based on isothermal sections, liquidus projections, and solidification curves that were calculated from the thermodynamic models of the Nb-Ti-Si-Cr-Hf system developed in the present study. This work provides important guidelines on the development of new Nb-Si-Ti-Cr-Hf alloys.
Microstructural characterization of copper metallic deposition by electroplating growth for SIP applications
Authors: Durand Céline , Domengès Bernadette , Le Duc Philippe 
Published: April 2011

ABSTRACTMicrostructural characterization (Focused Ion Beam and Transmission Electron Microscopy imaging) was performed on cross-sections of contacts in thick Electro Chemical Deposition copper metallization of System In Package Integrated Circuits. It was shown that the lower growth rate of ECD-Cu in the AlSiCu – barrier Ti – PVD-Cu – ECD-Cu layer stacking is related to a local higher resistivity induced by the presence of a great number of almost planar grain boundaries in the PVD-Cu layer, which are perpendicular to the growth axis. This morphology is a consequence of the almost heteroepitaxial growth of Ti layer on AlSiCu layer.
Crevice Corrosion Behavior of Type 316L Stainless Steel in Gamma-ray Irradiated High-temperature Water
Authors: Nakahara Yukio , Kato Chiaki , Yamamoto Masahiro , Tsukada Takashi , Watanabe Atsushi , Fuse Motomasa 
Published: April 2011

ABSTRACTCrevice-corrosion tests were performed in gamma-ray irradiated high-temperature water of 288 °C on Type 316L stainless steel. The gamma-ray dose rate was about 30 kGy h−1. Tested specimen surfaces were analyzed using SEM, laser Raman spectroscopy and TEM/EDX. Experimental data were presented in order to show the differences made by the irradiation and crevice-shape simulated structure. Both gamma-ray irradiation and crevice-shape simulated structure changed the corrosion phenomena. On the gamma-ray irradiated crevice-shape simulated surface, α-Fe2O3 particles more than 5 μm in diameter were observed. It suggested that corrosion environment on the crevice-shape simulated surface became severer by gamma-ray irradiation.
Magnetic Tight-Binding Simulations of Defects in Iron
Authors: Soin Preetma K. , Horsfield Andrew P. , Nguyen-Manh Duc 
Published: April 2011

ABSTRACTWe consider a tight binding model for magnetic systems, in which we allow atoms to become charged and to interact via the long ranged Coulomb interaction to a published tight binding model; this is then applied to the study defects in ferromagnetic iron. We encounter several problems with achieving self consistency with existing schemes. To address the issue of instability and slow convergency we developed a robust, efficient scheme for charge and spin self consistency. This is based on minimizing an extended form of the Harris-Foulkes functional which includes spin, leading to a Newton-Raphson iterative procedure. We then apply this to both bulk and defect calculations for iron.