bluuebunny/crossref_metadata_2025_split huggingface dataset:
Texture Memory Effect During Heat Treatment in the Heavily Cold Rolled Ni3Al Foils
Authors: Demura Masahiko , Xu Ya , Kishida Kyosuke , Hirano Toshiyuki 
Published: June 2019

AbstractTexture evolution during grain growth was examined in the 84% cold-rolled Ni3Al with a Goss texture, {110}<001>, using the electron backscatter diffraction method. By recrystallization at 873K/0.5h, the texture was disintegrated and composed of several orientations, most of which had a 40° rotation relationship about <111> to the Goss orientation. Also, a small number of the Goss grains existed. With grain growth, the Goss grains grew faster than the 40°<111> rotated grains, leading to the texture reversion to the original, Goss texture. This phenomenon can be referred to Texture memory effect. In the early stage of the grain growth, the preferential growth occurred on the Goss grains surrounded by the 40°<111> rotated grains. It can be thus ascribed to the high mobility of 40°<111> grain boundary. In the late stage, the Goss grains were adjacent to each other and the preferential growth was accelerated. It is considered that the adjacent Goss grains survived in the grain coalescence process since the boundary between them are low angle boundary having a low energy.
COMPRESSION CREEP BEHAVIOR OF B2 AL-NI-RU TERNARY ALLOYS
Authors: Cao Fang , Pollock Tresa M. 
Published: June 2019

AbstractThe compression creep behavior of five Al- Ni-Ru ternary alloys with compositions across the NiAl-RuAl B2 phase field has been investigated within the temperature range of 950 °C to 1050 °C. A continuous increase of the melting temperature and creep resistance with increasing Ru/Ni ratio in these alloys was observed. Post-creep dislocation analyses identified the presence of <100> and <110> edge dislocations in the Al-deficient alloys. Conversely, jogged <100> screw dislocations predominated in the Ru-rich ternary alloys. Dislocation substructures and transient experiments suggest a transition of the creep mechanism from viscous glide controlled to jogged screw motion in these alloys.
Structural transformations and improved ductility in ordered FeCo and ZrCo intermetallics
Authors: Krcmar Maja , Fu Chong Long , Morris James R. 
Published: June 2019

AbstractUsing the first-principles calculations, we find that Fe-Co has a tendency for a structural transformation to a lower symmetry sheared L10 phase under the applied shear stresses. This tendency for structural transformation can have a significant influence on the mechanical properties of FeCo, as it might be closely connected with the intrinsic brittleness of Fe-rich and stoichiometric FeCo alloys and with the improved ductility of Co-rich FeCo alloys. We suggest that improved ductility in Co-rich FeCo alloys may originate from transformation toughening due to the B2→L10 structural transformation near the regions of high stress concentration, as the stress energy is fully dissipated by the decrease in the electronic energy due to the structural phase transformation into a lower energy structure. Similarly, in ZrCo, our first-principles calculations find that a B2→B33 martensitic phase transformation can occur under the applied shear stress, which may contribute to the good ductility of this alloy, despite the fact that ZrCo is a strongly ordered line compound.
The Effect of Constraints on Plastic Deformation
Authors: Paidar Vaclav 
Published: June 2019

AbstractThe effect of the deformation constraints is examined for the lamellar structure of TiAl where the unconstrained plastic deformation occurs parallel to the lamellae. The constraints generally redistribute the stresses in such a way that the resolved shear stresses are decreased on the most stressed systems and increased on other systems. This behaviour leads to the material strengthening and may enhance the ductility when more deformation modes are activated.
Cold-Deformation and Annealing of equiaxed L1o-ordered FePd Intermetallics
Authors: Desphande Anirudha , Wiezorek Jorg 
Published: June 2019

AbstractThe L10 ordering equiatomic intermetallic FePd has been used as a model system for the investigation of the evolution of microstructure and properties during annealing at temperatures below the ordering temperature after deformation in the L10 state. The two different routes for the preparation of equiaxed L10 FePd polycrystals, annealing after cold deformation in the disordered FCC state or after cold deformation in the ordered state, produce similar grain size distributions, differ in the transformation kinetics and importantly in the sequence of texture evolution during the post-cold-deformation annealing. Cold deformed L10 FePd progresses through the classic stages of annealing known from studies of disordered elemental metals and alloys based on them. The reduced L10 SLRO of the ‘mechanically disordered’ FePd is recovered in the early stages of annealing and both the recrystallization and the grain growth stages are quite sluggish, presumably because of the slow diffusion processes in the L10 lattice.
Thermoelectric properties of Ba-Ge based Type-III Clathrate Compounds
Authors: Kim Jung-Hwan , Okamoto Norihiko L. , Kishida Kyosuke , Tanaka Katsushi , Inui Haruyuki 
Published: June 2019

AbstractThe crystal structures and thermoelectric properties of Ba-Ge based type-III clathrate compounds in Ba-Al-Ge and Ba-In-Ge systems have been investigated as a function of Al and In content. The absolute values of electrical resistivity and Seebeck coefficient increase, while that of lattice thermal conductivity decreases with increasing Al and In content. The increase in electrical resistivity and Seebeck coefficient is discussed in terms of the number of the excess electrons deduced from the Zintl concept, on the other hand, the decrease in lattice thermal conductivity is discussed in terms of an anisotropic deformation of the open-dodecahedron cage encapsulating Ba atom. High ZT values of 0.74 and 0.87 are obtained at 780 and 580 °C for Ba24Al12Ge88 and Ba24In16Ge84, respectively.
Classification and Characterization of the Shape Memory Binary Alloys
Authors: Notomi Mitsuo , Van Vliet Krystyn J , Yip Sidney 
Published: June 2019

AbstractAll shape memory binary alloys (SMBA) that exhibit not only perfect shape recovery but also partial shape recovery were reviewed and classified into three groups, B2, A2 and A1 type, according to the parent phases. There are the thirteen, six and eleven alloys belonging to B2, A2 and A1 type, respectively. In the group of B2 type SMBA the alloys are divided into two categories due to the combination of the elements. Over A1 and A2 type SMBA the atomic composition of one element is larger than the other so the larger one is called a major element. The major elements, Ti, U, Fe, and Cu, of A2 type SMBA do not belong to the group 5 and 6 in which the elements have a typical BCC (A2) crystal structure. In the A1 type SMBA there are four major elements, Mn, Fe, Co, and In and the SMBA except for In-based SMBA have ferromagnetic or antiferromagnetic natures. The shape memory effect (SME) for A1 (FCC) type SMBA might need the magnetic properties.
Structure Models of Massively Transformed High Niobium Containing TiAl Alloys
Authors: Scheu Christina , Cha Limei , Sturm Saso , Chladil Harald F. , Mayrhofer Paul H. , Clemens Helmut , Wolf Walter , Podloucky Raimund 
Published: June 2019

AbstractAb-initio calculations using the Vienna ab-initio simulation package (VASP) were performed for a high Nb bearing γ TiAl based alloy with a composition of Ti-46at.%Al-9at.%Nb in order to evaluate the effect of Nb on the crystal structure. The calculations revealed that upon doping with Nb the resulting structure can have Ti and Nb atoms on Al-sites, which leads to a reduction of the c/a ratio of the tetragonal γ TiAl cell to ~1.In contrast, the c/a ratio is increased, compared to the binary phase, if the Nb atoms occupy solely Ti sites and if Ti antisite defects (i.e. Ti on the Al sublattice) are formed. The relaxed structure models were used to perform high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image simulations. The results showed that the positions of the Nb atoms should be detectable by these high spatial resolution methods, although it might be easier by HAADF-STEM investigations due to the stronger dependence of the signal on the atomic number Z.
Phase Transitions and Recrystallization in a Ti-46at%Al-9at%Nb Alloy as Observed by In-Situ High-Energy X-ray Diffraction
Authors: Liss Klaus-Dieter , Clemens Helmut , Bartels Arno , Stark Andreas , Buslaps Thomas 
Published: June 2019

AbstractHigh-energy synchrotron X-ray diffraction is a powerful tool for bulk studies of materials. In this investigation, it is applied to the investigation of an intermetallic γ-TiAl based alloy with a composition of Ti-46Al-9Nb. The morphology of the reflections on the Debye-Scherrer rings is evaluated in order to approach grain sizes as well as crystallographic correlations. An in-situ heating cycle from room temperature to a temperature above the α-transus temperature has been conducted starting from a massively transformed sample. With increasing temperature the occurrence of strain relaxation, chemical and phase separation, domain orientations, phase transitions, recrystallization processes, and subsequent grain growth can be observed. During cooling to room temperature, crystallographic correlations between the re-appearing γ-phase and the host α-phase, known as the Blackburn correlation, are observed in the reciprocal lattice, which splits into different twinning and domain orientation relationships present in the fully lamellar microstructure.
Magnetron Sputtered Intermetallic Al2Au and Al-Zr-Y Coatings for the Oxidation Protection of γ-TiAl
Authors: Moser Martin , Mayrhofer Paul Heinz , Braun Reinhold 
Published: June 2019

AbstractAl-based intermetallic coatings are widely used as bond coats and for oxidation protection of turbine blades and engine components. Here we present and discuss the structural and thermal properties of novel unbalanced-magnetron sputtered Al-based coatings (single-phase intermetallic Al2Au, binary Al-Zr, and nano-structured Al-Zr-Y) developed to protect gamma-TiAl from environmental attack at elevated temperatures. Al-Zr films exhibit a coarse-grained dual-phase Al3Zr2-Al2Zr structure and are nano-structured by alloying with ~5, 10, and 14 at% Y.Combined dynamic differential-scanning calorimetry and thermogravimetric analyses up to a temperature of 1150 °C reveal that the Al2Au film is very stable with only marginal mass gain from oxidation found between 800 and 1000 °C. High temperature X-ray diffraction shows that this coating retains its (311) texture up to 900 °C where Al2O3 formation leads to the depletion of Al in Al2Au and subsequently the precipitation of intermetallic AlAu. When gamma-TiAl is coated with Al2Au and exposed to cyclic oxidation tests at 750 and 850 °C good oxidation resistance is obtained as a protective oxide layer is formed.Dual-phase Al3Zr2-Al2Zr coatings form ZrO2 and Al2O3 in oxidizing atmosphere. However, the phase transition from monoclinic (m-)ZrO2 to tetragonal (t-)ZrO2 with the accompanying volume change causes flaking of the oxide. Yttrium addition to the Al-Zr films stabilizes the cubic (c-) and t-ZrO2 and hence avoids the fatal tetragonal-monocline transformation. The thermally grown c-ZrO2 based oxides allow good adhesion to thermal barrier coatings which are themselves based on c-ZrO2.
Evolution and Interaction of Dislocations in Intermetallics: Fully Anisotropic Discrete Dislocation Dynamics Simulations
Authors: Chen Qian , Biner Bulent 
Published: June 2019

AbstractIn this study, the origin of large ductility that is seen in recently discovered rare-earth intermetallic compounds: YCu, YAg and YZn is explored by using fully anisotropic 3D dislocation dynamics simulations. The stability of the glide dislocations, the behavior of the Frank-Read sources and the strength of junctions are evaluated and compared to those seen for the common intermetallics, NiAl and Fe-25Al.
Microstructural Evolution of Dual Multi-Phase Intermetallic Alloys Composed of GCP Ni3Al and Ni3V Phases Containing Ti
Authors: Takasugi Takayuki , Kaneno Yasuyuki , Tsuda Hiroshi 
Published: June 2019

AbstractThe microstructural evolution of intermetallic alloys, which have dual two-phase microstructure composed of Ni3Al (L12) and Ni3V (D022) phases, was investigated as a function of aging time at 1273K by TEM. At early aging time, the lower microstructure showed structurally decomposed clusters composed of L12 phase and three D022 variant structures. With proceeding aging time, the decomposed L12 and D022 phases coarsened and transformed to lamellar-like microstructures. At longer aging time, the L12 phase disappeared from the lamellar-like microstructure and alternatively the D022 phase composed of two different variant structures prevailed over the lamellar-like microstructures. Corresponding to this microstructural change, the direction of the lamellar and its interfacial plane rotated from <001> to <011> and from {001} to {011}, respectively.
Tensile Property of Cold-Rolled Foils of Ni-Based and Co-Based L12 Intermetallic Alloys
Authors: Kaneno Yasuyuki , Takasugi Takayuki , Myoki Tadamichi 
Published: June 2019

AbstractPolycrystalline L12-type Ni3(Si,Ti), Co3Ti and Ni3Al alloys prepared through the thermomechanical process from arc-melted ingots were successfully cold-rolled to thin foils with a thickness of below 200μm. The cold-rolling with over 90% reduction in thickness was possible without providing intermediate annealing. The cold-rolled foils showed high tensile strength (~2GPa) at room temperature due to heavily cold rolling although no plastic elongation was observed. Room temperature tensile elongation increased with increasing annealing temperature, and reached to ~30-40% by high temperature annealing at 1173K. Among three kinds of intermetallic alloys, the Ni3(Si,Ti) foil annealed around at 900K exhibited an extremely high tensile strength and yield strength (over 2GPa) with a reasonable tensile elongation. The observed tensile properties, especially tensile strength at low temperature for the present intermetallic foils were found to be superior to those for the conventional alloys such as nickel based alloys and stainless steels.
Phase-Separations of Coherent Precipitates of Ordered Phases in Elastically Constrained Alloys
Authors: Doi Minoru , Kumagai Hiroshi , Nakashima Kanako , Kozakai Takao 
Published: June 2019

AbstractPhase-separations of coherent precipitates of ordered phases were investigated by means of transmission electron microscopy (TEM) and the theoretical analysis from a thermodynamic point of view. When the two-phase microstructures of A1+L12 in elastically constrained Ni-Al-Ti and Ni-Si-Fe alloys are isothermally heated inside the two-phase region of A1+L12 , coherent L12 precipitate particles sometimes exhibit a phase-separation and A1 phase newly appears and grows in L12 particles. Phase-separations of the same type as the above are also observed in coherent two-phase microstructures of A2+D03 and A2+B2 in elastically constrained Fe-Si-V and Fe-Al-Ni alloys respectively: coherent D03 or B2 precipitates exhibit a phase-separation and A2 phase newly appears and grows in both precipitates. Such phase-separation is realized under the influence of chemical free energy and elastic energies.
Microstructure and Hydrogen Permeability of Duplex Phase M-ZrNi (M=V, Nb, Ta) Alloys
Authors: Ishikawa Kazuhiro , Kasagami Naoshi , Takano Tomoyuki , Aoki Kiyoshi 
Published: June 2019

AbstractIn order to develop non-Pd based high performance hydrogen permeation alloys, microstructure, crystal structure and hydrogen permeability of duplex phase M-ZrNi (M=V and Ta) alloys were investigated using a scanning electron microscope, an X-ray diffractometer and a gas flow meter. These results were compared with those of Nb-ZrNi ones which have been previously published. The hydrogen permeation was impossible in the V-ZrNi alloys, because they were brittle in the as-cast state. On the other hand, duplex phase alloys consisting of the bcc-(Ta, Zr) solid solution and the orthorhombic ZrNi (Cmcm) intermetallic compound were formed and hydrogen permeable in the Ta-ZrNi system. The Ta40Zr30Ni30 alloy shows the highest value of hydrogen permeability of 4.1×10-8 [molH2m-1s-1Pa-0.5] at 673 K, which is three times higher than that of pure Pd.
Effect of C11b-Stabilized Element on Deformation Mode in C40-Type (Nb1-xMox)Si2 (x=0-0.85) Single Crystals
Authors: Nakano Takayoshi , Hagihara Koji , Umakoshi Yukichi 
Published: June 2019

AbstractPlastic deformation behavior and the dominant deformation mode in ternary (Nb1-xMox)Si2 (x=0-0.85) single crystals with the C40 structure were examined focusing on the phase stability between the C40 and C11b structures. Temperature dependence of CRSS for the (0001)<2-1-10] slip is strongly influenced by the Mo concentration accompanied by the change in the dissociation mode from the co-planar-type to the synchroshear-type. In the ternary crystals with x=0-0.30, anomalous strengthening clearly appeared, and the peak stress increased up to 1600¢ªC with an increase in the Mo content. Mo atoms may gather and form a dragging atmosphere around 1/3<2-1-10] dislocations containing a superlattice intrinsic stacking fault (SISF), resulting in anomalous strengthening. In contrast, in crystals with x=0.60-0.85, a high CRSS was obtained with fracture in a brittle manner at low temperatures, and the stress decreased remarkably with an increase in the test temperature. HRTEM observation showed that the synchroshear-type dissociation of each super-partial dislocation, 1/6<2-1-10], occurred on the neighboring slip planes, accompanied by a much wider separation distance of SF than that in the ternary crystals with a low Mo content. This change in plastic deformation behavior may be closely related to the decrease in phase stability of the C40 structure with the addition of the C11b-stabilized element, Mo. The phase stability can be represented by the ratio of (h/b), where h is the (0003) spacing and b is the amplitude of 1/3<2 0]. As the (h/b) ratio increases with the addition of Mo, the dissociation mode changes from the co-planar-type to the synchroshear-type at a ratio of 0.465.
Coercivity in nanostructured FeCo-based powders prepared by mechanical alloying
Authors: Zeng Qi , Baker Ian , McCreary Virginia , Yan Zhicheng 
Published: June 2019

AbstractFeCo-based nanostructured powders were prepared by mechanical alloying and subsequently heat treated in an attempt to reduce their coercivity, HC. Although the powders had grain sizes smaller than the magnetic exchange length, a low HC, as expected from Herzer's model, did not occur. The results of magnetic measurements on dilute and concentrated samples of the powder, as well as measurements of the temperature dependence of the magnetic properties from 10-300 K, indicate that the degree of magnetic interaction between the individual powder particles determines the relatively high HC of 10-20Oe at room temperature.
Room Temperature Ductility of B2-Type CoZr Intermetallic Compounds
Authors: Kaneno Yasuyuki , Takasugi Takayuki , Yoshida Mitsuhiko , Tsuda Hiroshi 
Published: June 2019

AbstractB2 (CsCl) CoZr intermetallic alloys with different chemical compositions were hot-rolled and subsequently recrystallized to evaluate tensile properties and rolling workability. Co-49.0Zr, -49.5Zr and -50.0Zr alloys showed the B2-matrixed microstructure containing C15 Co2Zr dispersions, while Co-50.5Zr and -51.0Zr alloys showed the B2-matrixed microstructure containing C16 CoZr2 dispersions. These homogenized ingots were successfully hot-rolled without edge cracks, except for the Co-51.0Zr alloy. The tensile tests revealed that the Co-49.5Zr, -50.0Zr and -50.5Zr alloys exhibited a notable tensile ductility at room temperature as well as at elevated temperatures. Moreover, the recrystallized CoZr alloys were cold-rolled up to 70% reduction without intermediate annealing. It was also found that tensile ductility was most prominent in the Co-50.0Zr alloy with the least volume fraction of second phase dispersions in the investigated alloys, suggesting that the B2 phase of CoZr was inherently ductile. Deformation microstructures were characterized by means of XRD and TEM observations. Mechanisms responsible for the observed large tensile ductility of the CoZr alloys were discussed, on the basis of the observed deformation microstructures.
On The Influence of Nb on the Transition Temperatures of Titanium Aluminides
Authors: Chladil Harald F. , Clemens Helmut , Takeyama Masao , Kozeschnik Ernst , Bartels Arno , Gerling Rainer , Kremmer Sascha 
Published: June 2019

AbstractPhase transformations and phase transition temperatures in several Ti-45Al and Ti-45Al-(5-10)Nb (at%) alloys were investigated experimentally and compared to thermodynamic calculation. The present study combines scanning electron microscopy, high-energy and conventional X-ray diffraction as well as differential scanning calorimetry for the characterization of the prevailing phases and phase transformations. Thermodynamic simulation based on the CALPHAD method was used to predict phase stabilities. Modifications of a commercial available database, based on the thermo-physical measurements and long-term annealing treatments, were introduced in order to achieve better agreement between calculated and experimental results.
Catalytic Properties of Ni3Al Foils for Hydrogen Production
Authors: Hirano Toshiyuki 
Published: June 2019

AbstractWe have successfully developed thin foils of boron-free Ni3Al (below 100 μm in thickness) by cold rolling, and recently found that the foils exhibit high catalytic activity for methanol decomposition. A little has been known about catalytic activity in Ni3Al. Even more interestingly, the high catalytic activity appears on flat foils whose surface area is very low. This paper provides a review of the characteristic features of the catalytic properties investigated in my group. Methanol was effectively decomposed into H2 and CO over the foils above 713 K. The production rates of H2 and CO increased with an increase of time during the initial period of reaction, indicating that the Ni3Al foils were spontaneously activated under the reaction conditions. Surface analyses revealed that fine Ni particles dispersed on carbon nanofibers formed on the foils during the reaction. The high catalytic performance of the foils can be attributed to the spontaneous formation of this nanostructure during the reaction.
High Temperature Strength of Co-based γ/γ' Superalloys
Authors: Suzuki Akane , DeNolf Garret C , Pollock Tresa M 
Published: June 2019

AbstractThe high temperature strength of new Co-Al-W based alloys consisting of a ?-Co (fcc) matrix phase and a high volume fraction of ?'-Co3(Al, W) ternary L12 intermetallic compound has been examined in order to understand the strengthening mechanisms and to explore the possibility for high temperature applications. The flow stress exhibits a strong, positive dependence on temperature above 873 K. Additions of Ta improve the high temperature strength, and the strength of a Ta containing alloy is comparable to Ni-base superalloys at 1173 K. Transmission microscopy on the deformed Ta containing alloy revealed that the active slip modes within the ?' precipitates are <110>{111} and <112>{111} below and above the peak temperature, respectively. At the peak flow temperature, multiple slip modes including <110>{111}, <110>{001} and <112>{111} were observed.