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  • Influence of unique layered microstructure on fatigue properties of Ti-48Al-2Cr-2Nb alloys fabricated by electron beam melting
    Intermetallics (IF 3.42) Pub Date : 2018-02-03
    Ken Cho, Ryota Kobayashi, Jong Yeong Oh, Hiroyuki Y. Yasuda, Mitsuharu Todai, Takayoshi Nakano, Ayako Ikeda, Minoru Ueda, Masao Takeyama
    更新日期:2018-02-04
  • Application of laser remelting process on the Zr-Cu based alloy composite
    Intermetallics (IF 3.42) Pub Date : 2018-02-03
    Huei-Sen Wang, Hou-Guang Chen, Yi-Ting Liu, Jason Shian-Ching Jang

    In this study, a 1.0 mm thick (Zr48Cu32Al8Ag8,Ta4)Si0.75 alloy composite (AC) plate was laser remelted (LR) by employing the Nd:YAG laser technique. To fully remelt the plate, a two-sided welding process with preselected parameters was employed. The microstructure, mechanical (microhardness), thermal properties, and corrosion resistance (potentiodynamic polarization) of the laser remelted alloy composite (LR-AC), the Zr-Cu AC (with the crystalline structure), and the Zr-Cu based bulk metallic glass composite (BMGC, the same composition as the AC. The amorphous matrix is produced by a rapid cooling rate) were then investigated and compared. The test results show that after the laser remelting processes, the LR-AC consisted of an amorphous matrix and reinforced phase, Ta, in the remelted areas, which is similar to the BMGC; however, the volume fractions and grain size of the micro-sized reinforced phase, Ta, in the LR-AC were reduced. When compared to those of the BMGC, the GFA indices of LR-AC were slightly improved. For the hardness tests, LR-AC showed a similar hardness to that of the BMGC; however, a higher value was obtained when compared to that of the AC. Furthermore, the LR-AC exhibits a lower Icorr (a slower corrosion rate), which is attributed to the amorphous matrix and less micro-sized Ta content, eliminating corrosion occurring between the Ta and the matrix of the alloy.

    更新日期:2018-02-04
  • Ferromagnetic ordering in the novel ternary uranium germanide URu0.29Ge2
    Intermetallics (IF 3.42) Pub Date : 2018-02-03
    M. Pasturel, A. Pikul, G. Chajewski, H. Noël, D. Kaczorowski

    URu0.29Ge2 is a new germanide crystallizing in a monoclinic structure (C2/c space group, lattice parameters: a = 4.098(1) Å, b = 15.936(3) Å, c = 4.045(1) Å and β = 90.091(2)°) derived from the CeNiSi2-type. It undergoes a ferromagnetic ordering at TC = 63 K, which manifests itself as distinct anomalies in temperature variations of the magnetization, specific heat and electrical resistivity. Just below TC, the T-dependent resistivity exhibits a broad hump, which hints at complex magnetic structure of the compound, while below 5 K it shows an upturn that likely arises due to atomic disorder in the crystal lattice.

    更新日期:2018-02-04
  • Effect of solution and aging treatment on the microstructure and tensile properties of SiCf/C/Mo/Ti2AlNb composites
    Intermetallics (IF 3.42) Pub Date : 2018-02-03
    X. Luo, J.J. Xu, Y.Q. Wang, Y.Q. Yang, M.A. Umer, S.Q. Zhang

    SiCf/C/Mo/Ti2AlNb composites were prepared by foil-fiber-foil (FFF) method and are used as model system to study the effect of solution-ageing treatments on the interface and mechanical properties of SiC fiber-reinforced TiAl-matrix composites. By contrast, SiCf/C/Ti2AlNb composites were prepared and heat treated under the same process parameters. The interfacial microstructures of the as-prepared and heat treated composites were investigated by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Tensile strength tests of the composites were carried out at room temperature. So the effect of C/Mo duplex coated SiC fibers on the microstructure and tensile behavior of the composites was studied. The results reveal that the interfacial thermal stability and integrity of the SiCf/C/Mo/Ti2AlNb composites are much better than those of the SiCf/C/Ti2AlNb composites, as the C/Mo duplex coating can reduce the formation of brittle α2-phase and relieve the interfacial thermal residual stresses in SiCf/Ti2AlNb composites compared with C single coating. After the 1080 °C/1 h/850 °C/20 h heat treatment, the matrix of the SiCf/C/Mo/Ti2AlNb composite transformed into mainly B2+O homogenous mixture and a small amount of α2 phase, and the tensile strength of the composite was tested, which shows that the tensile properties of the composite was maintained after the solution-ageing treatment.

    更新日期:2018-02-04
  • Precipitation behavior and mechanical properties of Ti-Ni-Nb-Co alloys
    Intermetallics (IF 3.42) Pub Date : 2018-02-03
    Bo Cui, Jian Yao, Ye Wu, Xin Zhang, Fuli Wang, Jiehe Sui, Wei Cai
    更新日期:2018-02-04
  • Microstructure of intermetallic-reinforced Al-Based alloy composites fabricated using eutectic reactions in Al–Mg–Zn ternary system
    Intermetallics (IF 3.42) Pub Date : 2018-02-03
    Naoki Takata, Taiki Okano, Asuka Suzuki, Makoto Kobashi

    We designed two types of Al-based alloy composites reinforced by η-Zn2Mg (hexagonal) and T-Al6Mg11Zn11 (cubic) intermetallic phases using monovariant eutectic reactions in the Al–Mg–Zn ternary system and then attempted to fabricate them using solidification. Thermodynamic assessment revealed two alloy compositions of Al–18Mg–36Zn and Al–22.5Mg–23.5Zn (at%) with the α-Al (fcc) phase reinforced with high fractions (>50%) of the η and T phases. Both alloys exhibited fine two-phase eutectic microstructures consisting of α/η and α/T phases, respectively. The morphology of the α-Al phase in the eutectic colonies varied from lamellae to fibers upon changing the neighboring intermetallic phase. These eutectic microstructures exhibit high stability at an elevated temperature of 300 °C. In addition, the size and spacing of the α-Al phase could be controlled by changing the cooling rate during solidification. The fabricated composites exhibited high hardness values exceeding 220 HV, which were much superior to those of conventional Al alloys. The calculated solidification path and component partitioning in the liquid phase during solidification provided insights into the solidification segregation of Zn element in the Al–18Mg–36Zn alloy. The Zn-enriched regions would enhance the local microstructural change at elevated temperatures, which confirmed by the microstructural observations of the alloy exposed at 300 °C.

    更新日期:2018-02-04
  • (TiZrNbTa)-Mo high-entropy alloys: Dependence of microstructure and mechanical properties on Mo concentration and modeling of solid solution strengthening
    Intermetallics (IF 3.42) Pub Date : 2018-02-03
    Shao-Ping Wang, Jian Xu

    In this work, the evolution of microstructure and fundamental mechanical properties with Mo concentration in the arc-melted (TiZrNbTa)100-xMox (0 ≤ x ≤ 20) high-entropy alloys (HEAs) are investigated. The arc-melted (TiZrNbTa)100-xMox alloys structurally consist of two bcc phases. The change in volume fractions of two phases in the microstructure is insignificant with Mo concentration, at levels of ∼75% for bcc1 and ∼25% for bcc2. The increases in microhardness and Young's modulus of the alloys linearly scale with Mo concentration. To compromise the strength and ductility, the (TiZrNbTa)90Mo10 exhibits an optimal combination of stiffness (E = 137 GPa), compressive yield strength (σy = 1370 MPa) and deformability (εp ≈ 25%). In addition, it is indicated that dislocation widths in bcc lattice of refractory HEAs are insensitive to the alloying complexity, reflecting that the Peierls barrier is excluded as a predominant factor of strengthening. Furthermore, a simple model is proposed to reveal the solid solution hardening (SSH) in bcc refractory HEAs, in which the solid solutions are treated as an imposition of distortion-free and distorted lattices. By applying this model to archived refractory HEAs, the predicted yield strength agrees well with experimentally measured values. It provides a simple empirical tool used for predicting the strength of bcc refractory HEAs and to assist new alloy design.

    更新日期:2018-02-04
  • Hydrogen storage properties of LaMg4Cu
    Intermetallics (IF 3.42) Pub Date : 2018-02-03
    Xiaojing Jiang, Yong Wu, Kai Fu, Jie Zheng, Xingguo Li

    A new LaMg4Cu intermetallic compound with hexagonal UCoAl4 type structure is prepared by induction melting and subsequent heating treatment. The compound rapidly absorb 3.3 wt% hydrogen at 573 K under 4.0 MPa H2 for the first cycle, leading to phase segregation into LaH3, MgH2 and MgCu2. The reversible dehydrogenation capacity is 2.6 wt% at 523 K, forming a mixture of LaH2, Mg and Mg2Cu. The PCT curves show two plateaus corresponding to the formation of Mg and Mg2Cu, respectively. Compared with mechanically manufactured Mg and bulk Mg2Cu alloy, our in-situ generated LaH2, Mg and Mg2Cu mixture exhibits excellent kinetics and cycling properties, which is mainly attributed to the La-Mg-Cu-H nanostructures via the hydrogen-induced decomposition of LaMg4Cu intermetallic compounds.

    更新日期:2018-02-04
  • Mapping the magnetic transition temperatures for medium- and high-entropy alloys
    Intermetallics (IF 3.42) Pub Date : 2018-02-03
    Shuo Huang, Erik Holmström, Olle Eriksson, Levente Vitos
    更新日期:2018-02-04
  • Fe87Zr7B4Co2 amorphous alloy with excellent magneto-caloric effect near room temperature
    Intermetallics (IF 3.42) Pub Date : 2018-02-03
    P. Yu, J.Z. Zhang, L. Xia

    A Fe87Zr7B4Co2 amorphous alloy with excellent magneto-caloric effect near room temperature was fabricated in the present work. The amorphous alloy exhibits typical soft magnetic behavior with nearly zero coercivity at a sub-ambient temperature. The glassy ribbon presents a rather high peak value of magnetic entropy change and refrigeration capacity near room temperature compared to other Fe-based amorphous alloys, indicating that the amorphous alloy is a good component of magnetic refrigerants near the hot end of a magnetic air conditioner.

    更新日期:2018-02-04
  • Long-term creep behaviour of cast TiAl-Ta alloy
    Intermetallics (IF 3.42) Pub Date : 2018-01-20
    J. Lapin, T. Pelachová, M. Dománková
    更新日期:2018-01-20
  • Unusual crystallization of Al85Y8Ni5Co2 metallic glass observed in situ in TEM at different heating rates
    Intermetallics (IF 3.42) Pub Date : 2018-01-17
    A.I. Bazlov, N. Yu Tabachkova, V.S. Zolotorevsky, D.V. Louzguine-Luzgin
    更新日期:2018-01-17
  • Bulk metallic dual phase glasses by severe plastic deformation
    Intermetallics (IF 3.42) Pub Date : 2018-01-12
    Lisa Krämer, Yannick Champion, Karoline S. Kormout, Verena Maier-Kiener, Reinhard Pippan
    更新日期:2018-01-13
  • Ordered intermetallic Pt-Fe nano-catalysts for carbon monoxide and benzene oxidation
    Intermetallics (IF 3.42) Pub Date : 2018-01-13
    Govindachetty Saravanan, K. Pulleri Jayasree, Yearwar Divya, Mungse Pallavi, Labhsetwar Nitin

    Conversion of toxic, indoor pollutants into innocuous products through catalytic reaction is one of the promising among other permanent solutions. γ-Al2O3 supported, Pt-based intermetallic nanoparticles (NPs) using abundantly available metal e.g., Fe (Pt-Fe; Pt3Fe and PtFe3) as catalysts are successfully prepared through a wet-impregnation method followed by calcination in the presence of H2 at 800 °C. Although the intermetallic Pt-Fe NPs are prepared at elevated temperatures, they are, however, not agglomerated and are finely dispersed on the γ-Al2O3 support with the average particle size between 4 and 6 nm. No other intermetallic or alloy phases of Pt-Fe were not observed under the set synthesis conditions. Despite the same Pt-mass loading in the both Pt-Fe catalysts, intermetallic PtFe3 catalysts showed much improved carbon monoxide (CO) oxidation activity by at least 8-fold compared to that of the intermetallic Pt3Fe catalysts. The intermetallic PtFe3 catalysts showed the enhanced activity for CO oxidation compared to that of the intermetallic Pt3Fe catalysts, however, both the intermetallic Pt-Fe catalysts showed virtually the same catalytic activity for benzene oxidation. Both the intermetallic Pt-Fe catalysts showed the stable, multi-cycle catalytic performance for the catalytic CO and benzene oxidation and retain their structure and morphology even after catalytic reaction.

    更新日期:2018-01-13
  • Superconductivity, Kondo effect, and observation of self-organized pattern formation in intermetallic NiBi3 thin films
    Intermetallics (IF 3.42) Pub Date : 2018-01-10
    Ekta Bhatia, Abhishek Talapatra, Jyoti Ranjan Mohanty, Kartik Senapati

    The superconducting properties of the intermetallic compound NiBi3 have been studied mostly in bulk crystals. In this report we have studied several aspects of NiBi3 thin films, spontaneously formed at the interface of Ni and Bi multilayers. We have observed superconducting transition around 3.9 K, close to the bulk transition temperature of 4.1 K. Due to the diffusive mechanism of formation of NiBi3, additional phenomena such as magnetic (Nickel) impurity induced Kondo effect and self organized Turing pattern formation also come into picture. From X-ray diffraction and Magneto-resistance measurements we have established the presence of atomic Ni impurities in the films. Kondo minima were found to scale with varied concentration of Ni impurities in a series of Ni-Bi multilayer films (with fixed Ni thickness and varied Bi thickness). Similarly, saturation magnetization and superconducting transition temperature were also found to follow the concentration of Ni impurities. In addition, we have also observed signatures of Turing patterns, from magnetic force microscopy, naturally formed with time without any external heat treatment.

    更新日期:2018-01-11
  • Microstructures and mechanical properties of C-containing FeCoCrNi high-entropy alloy fabricated by selective laser melting
    Intermetallics (IF 3.42) Pub Date : 2018-01-11
    Rui Zhou, Yong Liu, Chengshang Zhou, Siqin Li, Wenqian Wu, Min Song, Bin Liu, Xiaopeng Liang, P.K. Liaw

    Additive manufacturing (AM) is an emerging technology that has been widely used for fabricating components with highly complex shapes. In this work, C-containing FeCoCrNi high entropy alloy with full density was successfully fabricated using selective laser melting (SLM). The effects of processing parameters on the microstructures and mechanical properties were investigated, and the underlying mechanism was discussed. The density of HEA is dependent on the SLM processing parameter. The increase of the SLM scanning power or the decrease of the scanning speed leads to the increase of the density of HEA. The grain size reduced when the high scanning power or the low scanning speed was used. The C-containing HEAs with full density has a yield strength of 650 MPa, and an elongation of 13.5%.

    更新日期:2018-01-11
  • Structural disorder effects on the magnetic entropy change of DyCo2 intermetallic: Mechanical milling and the weakening of the itinerant electron metamagnetism mechanism
    Intermetallics (IF 3.42) Pub Date : 2018-01-04
    V.G. de Paula, M. Gomes Silva, L.M. da Silva, A.O. dos Santos, R. Lang, L. Otubo, A.A. Coelho, L.P. Cardoso

    Magnetocaloric properties of the intermetallic DyCo2 compound (in the form of reduced size particles) and its correlations with the itinerant electron metamagnetism (IEM) phenomenon and structural disorders are investigated and discussed. Micrometric-sized particles were prepared by a mechanical milling technique for two low milling times (4 and 8 h) and characterized by means of X-ray diffraction, scanning and high-resolution transmission electron microscopy as well as magnetic measurements as a function of an applied external magnetic field and temperature. The results show that the particles have irregular-shaped and amorphous “edges/ledges” with embedded randomly oriented DyCo2 nanocrystallites. The average particle size practically does not change with increasing milling time, whereas the average crystallite size is slightly diminished. In contrast, microstrain values that indicate lattice deformation degree were rather increased after the milling processes. Structural disorders and surface effects, features resulting from mechanical impact, disturb the Dy-Co sublattice coupling and weaken the IEM mechanism responsible for the high magnetocaloric effect found for the DyCo2 bulk sample. For the milled samples, it was observed reductions in the peak intensity of the magnetic entropy change (−ΔSM) and substantial broadenings of the distribution profiles which have contributed to an increase of the working temperature range of the investigated magnetocaloric material.

    更新日期:2018-01-10
  • Activation-relaxation technique study on β-relaxation in La55Ni20Al25 and Cu46Zr46Al8 metallic glasses
    Intermetallics (IF 3.42) Pub Date : 2017-12-21
    H.Y. Xu, M.Z. Li

    Activation-relaxation technique combined with molecular dynamics simulations was employed to investigate β-relaxation behavior in La55Ni20Al25 and Cu46Zr46Al8 model metallic glasses (MGs) for exploring the underlying mechanism. It is found that the activation energies are much smaller in La55Ni20Al25 MG, indicating that β-relaxation can be more easily activated in La55Ni20Al25 MG. It is also revealed that in both MGs, string-like diffusion dominates the atomic motions in β-relaxation. However, in different MGs, the string-like motions are found to involve atoms with different structure features, which could be the underlying structural basis of β-relaxation mechanism. In addition, because of very low activation energies, atomic hopping and cooperative rearrangements in La55Ni20Al25 MG also have significant impact on β-relaxation. However, such atomic motions are much weaker in Cu46Zr46Al8 MG, due to higher activation energies. These findings establish a physical link for activation energy and atomic motions in β-relaxation to atomic structures, and provide new understanding of β-relaxation mechanism in MGs.

    更新日期:2018-01-10
  • Metamagnetic transition and magnetocaloric properties in antiferromagnetic Ho2Ni2Ga and Tm2Ni2Ga compounds
    Intermetallics (IF 3.42) Pub Date : 2017-12-21
    Yikun Zhang, Yang Yang, Chunjuan Hou, Dan Guo, Xi Li, Zhongming Ren, Gerhard Wilde

    The structure, magnetic transition and magnetocaloric properties in the ternary gallium intermetallic compounds of Ho2Ni2Ga and Tm2Ni2Ga have been systematically investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and magnetization measurements. As found from powder XRD and Rietveld refinement, Ho2Ni2Ga and Tm2Ni2Ga crystallized in an orthorhombic structure of the W2B2Co type belonging to the Immm space group. Both compounds are ordering antiferromagnetically at low temperatures and under low magnetic fields together with a field-induced metamagnetic transition from antiferromagnetic (AFM) to ferromagnetic (FM). Peculiar and similar magnetocaloric properties are observed for both compounds, i. e., an inverse magnetocaloric effect (positive magnetic entropy change, ΔSM) under low magnetic field changes (ΔH) and at low temperatures together with a large normal reversible magnetocaloric effect under high ΔH. The positive ΔSM below/at the Néel temperatures (TN) is ascribed to first order transition from antiferromagnetic (AFM) to ferromagnetic (FM) states, whereas the negative ΔSM above TN is due to the fact of the magnetic transition from paramagnetic (PM) to ferromagnetic (FM) states. Based on the field-dependent magnetization data, the maximum magnetic entropy change (−ΔSMmax), relative cooling power (RCP) and refrigerant capacity (RC) are established, and the corresponding values are 9.6 J/kg K, 276 J/kg and 206 J/kg for Ho2Ni2Ga, and are 4.3 J/kg K, 60 J/kg and 46 J/kg for Tm2Ni2Ga, respectively, for a magnetic field change of 0–70 kOe.

    更新日期:2018-01-10
  • 3D printing of Zr-based bulk metallic glasses with complex geometries and enhanced catalytic properties
    Intermetallics (IF 3.42) Pub Date : 2017-12-21
    Chong Yang, Cheng Zhang, Wei Xing, Lin Liu

    Bulk metallic glasses (BMGs) are difficult to manufacture by conventional processes due to the superior strength and extreme brittleness of these materials. Here, we report on the manufacturing of Zr-based BMG components with complex geometries, including cubic, hollow, and lattice structures, by using a selective laser melting (SLM) 3D-printing technique. High amorphous phase fractions between 74 and 90 wt% are achieved depending on the geometries manufactured. To take advantage of complex geometries with large specific surface areas, the lattice BMG samples were selected, as an example, to be dealloyed to obtain a milli/nano hierarchical porous structure, which exhibits excellent catalytic properties towards degradation of methyl orange, showing a promising potential for functional applications.

    更新日期:2018-01-10
  • Effect of Au diffusion in Au-coated (γ + α2) titanium aluminides
    Intermetallics (IF 3.42) Pub Date : 2017-12-22
    Marie-Pierre Bacos, Mikael Perrut, Denis Boivin, Nicolas Horezan, Etienne Rimpot, Catherine Rio, Claire Sanchez

    In order to understand the role of α2-Ti3Al precipitates during the oxidation of Au-coated γ-48-2-2-TiAl alloys, the γ-TiAl and α2-Ti3Al microstructures resulting from Au diffusion at 900 °C were investigated. The as-obtained coatings were characterized using scanning electron microscopy (SEM), combined energy and wavelength dispersive X-ray spectroscopies (EDS, WDS), electron backscatter diffraction analysis (EBSD), X-ray diffraction (XRD) and isothermal oxidation tests. Results showed that Au-coated-γ-TiAl alloys presented an upper aluminoformer TiAlAu2 layer and a lower non-protective TiAlAu layer, both with narrow homogeneity range, and with thicknesses that could be estimated with the use of the Prasad model. A more complex layer structure is obtained after Au diffusion in α2-Ti3Al alloys, since eight different phases were identified. In the lower layers, two new ternary tetragonal phases (Ti2AlAu and Ti3Al2Au) were found, and a partial diagram for the Al-Au-Ti 900 °C isotherm is proposed. Absence or depletion of Al was found in the upper layers and, in addition, a low oxidation resistance of the Au-coated-α2-Ti3Al alloy was reported.

    更新日期:2018-01-10
  • Influence of Cu addition on the glass transition behavior of LaCe-based metallic glasses
    Intermetallics (IF 3.42) Pub Date : 2017-12-22
    L.J. Song, J.Z. Bi, R. Li, W. Xu, J.T. Huo, J.Q. Wang, X.M. Wang

    The effect of Cu content on glass transition behavior of (La0.5Ce0.5)65Al10Co25-xCux (x = 0, 5, 10, 15, 20, 25) metallic glasses was measured by high-rate and high-precision differential scanning calorimetry. It is observed that the glass transition temperature (Tg) decreases with the increase of the Cu content. The fragility (m) increases first and then decreases with the increasing of Cu content, with a maximum m = 63.6 for x = 10. A correlation is confirmed between the enthalpy of mixing fragility. These results suggest that metallic glasses with desirable supercooled liquids characters can be designed by alloying elements with suitable mixing enthalpy.

    更新日期:2018-01-10
  • Internal stresses influence on magnetic properties of Ni-Mn-Ga Heusler-type microwires
    Intermetallics (IF 3.42) Pub Date : 2017-12-23
    S. Shevyrtalov, A. Zhukov, V. Zhukova, V. Rodionova

    The influence of internal stresses on magnetic properties of Ni-Mn-Ga glass-coated microwire was investigated. Microwires with Ni63Mn12Ga25 chemical composition, full diameter D = 54.6 μm and metallic nucleus diameter d = 26.7 μm, were prepared by Taylor-Ulitovsky technique. An analysis of a separate influence of stresses, generated during the solidification of metal and those induced by the difference between thermal expansion coefficients of metal and glass, on magnetic properties of Ni-Mn-Ga microwire was done. Carrying out the heat treatment for a different time reveals the influence of the first type of stress. Removing the glass coating show the influence of the second type of stress. To analyze a complex influence of stresses we performed a heat treatment of the microwire after glass coating removal. The coercive force, saturation and remanence magnetization and Curie temperature were compared to show stresses influence. The change of easy magnetization axis direction was found for microwire with removed glass coating. A difference in surface grain size was indicated in the annealed glass-coated microwire and microwire, annealed after glass removal.

    更新日期:2018-01-10
  • Size effects of NiTi nanoparticle on thermally induced martensitic phase transformation
    Intermetallics (IF 3.42) Pub Date : 2018-01-04
    Zhibin Chen, Shengjian Qin, Jiaxiang Shang, Fuhe Wang, Yue Chen

    Molecular dynamics simulations are performed to study the thermally induced martensitic phase transformation (B2-B19′) of NiTi free-standing nanoparticles. We successfully reproduce the experimental observations that the martensitic transformation temperature decreases with reducing particle size and the martensite may form self-accommodated herringbone morphology. It is found that a core-shell structure with shell thickness of 0.3 nm (approximately equal to one unit cell) exists in NiTi nanoparticles and the B2-B19′ transformation is dominated by the core region. In addition, three detwinning manners are observed in the reverse martensitic phase transformation (B19′-B2) process. It is concluded that the suppression of B2-B19′ transformation in NiTi nanoparticles is due to the lack of nucleation sites and the size dependent martensitic morphology originates from the constraints of surface shell.

    更新日期:2018-01-10
  • Minimum interface misfit criterion for the precipitation morphologies of TCP phases in a Ni-based single crystal superalloy
    Intermetallics (IF 3.42) Pub Date : 2018-01-04
    Haibo Long, Yinong Liu, Shengcheng Mao, Hua Wei, Jianxin Zhang, Shiyu Ma, Qingsong Deng, Yanhui Chen, Ze Zhang, Xiaodong Han

    The precipitation and growth morphology of topologically close-packed (TCP) phases in a Re-containing Ni-based single crystal superalloy during thermal exposure were studied. The alloy was found to develop acicular-shaped coherent μ phase particles along <110>γ directions of the matrix after exposure at 950 °C. P phase precipitates were found to form with increased time and at higher temperatures, and in different morphologies, including acicular shaped particles along <112>γ and <110>γ directions, and plate-like particles in {110}γ planes of the matrix. The different P phase precipitates were found to have different lattice constants and different lattice correspondences with the matrix. The μ phase precipitate was also found to have different lattice correspondences with those reported in the literature. The multiplicity of lattice correspondences for the same TCP phase is attributed to the different lattice parameters, which render the precipitates to have different coherency relationships with the matrix.

    更新日期:2018-01-10
  • Effects of Ni-P amorphous films on mechanical and corrosion properties of Al0.3CoCrFeNi high-entropy alloys
    Intermetallics (IF 3.42) Pub Date : 2018-01-04
    Z.H. Xia, M. Zhang, Y. Zhang, Y. Zhao, P.K. Liaw, J.W. Qiao

    Through electroless plating, the Al0.3CoCrFeNi high-entropy alloys were successfully coated with the Ni-P amorphous film with a thickness of 1.2 μm. For studying the surface change of samples after chemical plating, the surface morphologies of the as-cast HEA substrate and HEA with the Ni-P film were contrasted by atomic-force microscopy. The tensile properties of the samples with and without the Ni-P film, and the deformational behavior of thin Ni-P film were researched, respectively. In addition, the effect of the Ni-P amorphous film on corrosion resistance of the coated HEAs was also investigated. The experimental results show that in contrast to the uncoated samples with a yielding strength of 275 MPa, the yielding strength of the coated samples exhibits 400 MPa, with a 45% improvement, which can be attributed to the very high yield strength of the Ni-P amorphous film. A tensile strain up to 10% was achieved in the Ni-P film since the propagation of one primary shear band was inhibited, and the stress/strain concentration was retarded by the plastic substrate. The corrosion resistance of the HEA with the Ni-P film is superior to that of the bare HEA in the 3.5 wt percent NaCl solutions due to the chemical homogeneity and the absence of microscopic defects in the Ni-P amorphous film. The current results indicate that the surface coating is an effective means for optimizing the properties of HEAs, and the thin Ni-P coating can remarkably improve the strength of the present HEAs.

    更新日期:2018-01-10
  • Thermodynamic investigations in the Al-Fe system: Heat capacity measurements of three intermetallic phases
    Intermetallics (IF 3.42) Pub Date : 2018-01-04
    Maximilian Rank, Petronela Gotcu, Peter Franke, Hans Jürgen Seifert

    For a comprehensive understanding of the Al-Fe systems' thermodynamics further experimental investigations are required, especially for the Al-rich side. Intermetallic phases in the Al-Fe system have been produced by arc-melting (stoichiometric compositions: Al2Fe, Al5Fe2 and Al13Fe4). The samples were heat treated at elevated temperatures and characterized using scanning electron microscopy, X-ray diffraction and inductive coupled plasma - optical emission spectrometry. Heat capacities were measured using independent heat flux differential scanning calorimeters in the temperature range from 223 K up to 1370 K. In general, the obtained data are lower than the estimations based on the Neumann-Kopp rule over a large temperature range. The heat capacity functions of the three intermetallic phases are represented by regression functions over the complete measured temperature intervals.

    更新日期:2018-01-10
  • Stability of lamellar structure of directionally solidified NiAl-28Cr-6Mo eutectic alloy at different withdrawal rates and temperatures
    Intermetallics (IF 3.42) Pub Date : 2018-01-04
    Lei Wang, Jun Shen, Guojun Zhang, Yunpeng Zhang, Lanlan Guo, Yuhui Ge, Luhan Gao, Hengzhi Fu

    Stability of lamellar structure of directionally solidified NiAl-28Cr-6Mo eutectic alloys was investigated at different withdrawal rates and temperatures. The result indicates that the lamellar structure has no significant change after various temperatures (900–1100 °C) at 2.5 μm/s. With increasing the withdrawal rate to 4.5 μm/s or 7.5 μm/s, no major change occurs in the lamellar structure at the temperature of up to 1000 °C, however, some little coarsening and migration of lamellar structure emerge at 1050 °C and 1100 °C. With increasing the withdrawal rate (decreasing the lamellar spacing), the stability of lamellar structure becomes poor. At the present experimental temperature (900–1100 °C, in particular, 1050 °C and 1100 °C), the migration, pinching off, coarsening, even spheroidization of Cr(Mo) phase are observed by mild etching. The deep etching and the observation of inclining 45° to growth direction improve the result about the pinching off and spheroidization of Cr(Mo) phase observed by mild etching. Actually, the local dissolution and the cylinderization of Cr(Mo) phase occur. The mechanism of lamellar degradation is discussed.

    更新日期:2018-01-10
  • Optimization of high frequency magnetoimpedance effect of Fe-rich microwires by stress-annealing
    Intermetallics (IF 3.42) Pub Date : 2018-01-04
    V. Zhukova, J.M. Blanco, M. Ipatov, M. Churyukanova, J. Olivera, S. Taskaev, A. Zhukov

    We present comparative studies of magnetic properties and giant magnetoimpedance (GMI) effect of Fe and Co-rich microwires. As-prepared Co-rich microwires present much higher GMI ratio. The impact of the stress-annealing on magnetic softness and high frequency magnetoimpedance effect of Fe-rich microwires has been studied. The large improvement of the magnetoimpedance response in a wide frequency range by the stress-annealing is observed. We have achieved GMI ratio increase by an order of magnitude after stress-annealing of Fe-rich microwire. Observed stress-induced anisotropy and related changes of magnetic properties are discussed considering internal stresses relaxation and “back-stresses”.

    更新日期:2018-01-10
  • Design of highly efficient Ni-based water-electrolysis catalysts by a third transition metal addition into Ni3Mo
    Intermetallics (IF 3.42) Pub Date : 2018-01-04
    Yanlin Yu, Qiang Hu, Wei Xiao, Jianwei Wang, Ligen Wang

    The surface composition segregation can have important effects on the catalytic and electrochemical properties of an alloy catalyst. We have performed density-functional theory (DFT) calculations to investigate the effects of a third transition metal (M) addition into the Ni3Mo alloy on the surface segregation and the stability of bulk-terminated and Ni-segregated Ni3Mo/M(111) surfaces. The third transition metals (MTc, Ru, W, Re, or Os) are found to enhance the Ni surface segregation, while MTi, V, Cr, Mn, Fe, Co, Cu, Nb, Rh, Hf, Ta, or Ir retain the Ni-segregated surface but weaken the Ni surface segregation tendency. The remaining transition metals (MSc, Zn, Y, Zr, Pd, Ag, Cd, Pt, or Au) show a complete suppression of the Ni surface segregation. We find the transition metals (Ti, V, Cr, Mn, Fe, Co, Cu, Hf, and W) can stabilize a special atomic configuration that is predicted to have an outstanding catalytic performance for water electrolysis. Furthermore, we analyze the factors that control the Ni surface segregation behavior in the Ni3Mo/M(111) surface. The present study provides useful theoretical guide for developing highly active Ni-Mo-M hydrogen evolution electrodes.

    更新日期:2018-01-10
  • Improving oxidation resistance of MoSi2 coating by reinforced with Al2O3 whiskers
    Intermetallics (IF 3.42) Pub Date : 2018-01-04
    Lu Wang, Qiangang Fu, Fengling Zhao

    To improve the toughness and oxidation resistance of MoSi2 coating, Al2O3 whiskers and Al2O3 particles were introduced respectively. The geometry of Al2O3 significantly influence the toughening effect on suppressing crack extension. After oxidation at 1450 °C for 76 h, MoSi2 coating reinforced with 1% Al2O3 whiskers lost mass of only 0.17% and remained integrity, compared to the particles with 0.70% and destroyed by penetrative cracks, exhibiting favorable oxidation resistance. The improved property resulted from the crack-healing by Al2O3·21SiO2 glass occurred during oxidation and better toughening effect by the whiskers to restrain crack growth. Noticeable, increased Al2O3 content made the coatings porous remarkably, and also decrease the crack resistance during oxidation, led to degradation of the ability to resist accelerated oxidation erosion.

    更新日期:2018-01-10
  • The effect of void defects on the shear band nucleation of metallic glasses
    Intermetallics (IF 3.42) Pub Date : 2018-01-04
    Yun Luo, Guannan Yang, Yang Shao, Kefu Yao

    Molecular dynamics simulations were employed to investigate the effect of void defect on the shear band nucleation in a Cu64Zr36 metallic glass. Unlike uniform samples, the samples with void defects can form shear bands at a much lower strain. Finite element simulation revealed stress concentration near the voids, which can explain the early formation of shear bands. The shear band behaviors are also influenced by the size, shape and distribution of the defects. These findings can provide simulation support to understand the shear band heterogeneous nucleation process of metallic glasses in the real case.

    更新日期:2018-01-10
  • Constitution of the binary M-Sb systems (M = Ti, Zr, Hf) and physical properties of MSb2
    Intermetallics (IF 3.42) Pub Date : 2018-01-06
    A. Tavassoli, A. Grytsiv, F. Failamani, G. Rogl, S. Puchegger, H. Müller, P. Broz, F. Zelenka, D. Macciò, A. Saccone, G. Giester, E. Bauer, M. Zehetbauer, P. Rogl
    更新日期:2018-01-10
  • Correlation between defects and magneto-structural properties in Ni-Mn-Sn metamagnetic shape memory alloys
    Intermetallics (IF 3.42) Pub Date : 2018-01-08
    J. López-García, I. Unzueta, V. Sánchez-Alarcos, V. Recarte, J.I. Pérez-Landazábal, J.A. Rodríguez-Velamazán, J.A. García, F. Plazaola

    The effect of combined mechanical and thermal treatments in the magnetostructural properties was studied in Ni-Mn-Sn metamagnetic shape memory alloys, in which the extraordinary high stability of the L21 structure precludes the variation of atomic order by means of conventional thermal treatments. A Ni50Mn35Sn15 alloy has been mechanically milled and then annealed at different temperatures in order to produce different microstructural states. The evolution of both the internal stresses and the crystallite size upon annealing has been quantified and correlated to the evolution of the martensitic transformation features and the magnetic properties. It is found that the relaxation processes brought by annealing leads to recovery of the martensitic transformation and the enhancement of the magnetism at both macroscopic and local level. In particular, the density of non-magnetic inclusions (defects) and their stress field decrease upon annealing, thus leading to an increase of the saturation magnetization and a decrease of the martensitic transformation temperature range, respectively, which results in a higher magnetocaloric effect. The obtained results confirm that, once the transition temperature has been fixed by the composition, the modification of the microstructure through thermomechanical treatments appears as the best way to tune the functional properties of these alloys.

    更新日期:2018-01-10
  • Hot deformation behavior and processing maps of B and Gd containing β-solidified TiAl based alloy
    Intermetallics (IF 3.42) Pub Date : 2018-01-08
    V.S. Sokolovsky, N.D. Stepanov, S.V. Zherebtsov, N.A. Nochovnaya, P.V. Panin, M.A. Zhilyakova, A.A. Popov, G.A. Salishchev
    更新日期:2018-01-10
  • Microstructure control and creep behavior of Ti-47Al-6Nb-0.1C alloy by directional solidification
    Intermetallics (IF 3.42) Pub Date : 2018-01-08
    Qi Wang, Ruirun Chen, Xue Gong, Jingjie Guo, Yanqing Su, Hongsheng Ding, Hengzhi Fu

    Newly designed Ti-47Al-6Nb-0.1C at.% alloy was directionally solidified by cold crucible under 45 kW at the growth rate of 5–16.67 μm/s. The macro/microstructure evolution, room-temperature tensile property and creep behavior are investigated. The results show that this alloy was well directionally solidified by cold crucible at the growth rate of 5–11.67 μm/s, and they display primary β solidification at this growth-rate range. It is also found that the lamellar spacing is mainly controlled by growth rate, and the lamellar spacing decreases with the increasing of growth rate according to relationship d=1751V−0.58 d = 1751 V − 0.58 . Moreover, the extent of microsegregation increases with the increasing of growth rate, and thus the effect of microsegregation on creep behavior is discussed. After controlling directional solidification process at growth rate of 5–8.33 μm/s, this alloy exhibits good creep properties with creep life more than 800 h at 800 °C/200 MPa, and the acceptable room-temperature tensile property with yield strength 436–452 MPa and elongation 1.62–1.68%.

    更新日期:2018-01-10
  • Enhanced magnetocaloric properties in off-stoichiometric LaxFe11.5Si1.5 alloys
    Intermetallics (IF 3.42) Pub Date : 2017-11-23
    G.F. Wang, Z.R. Zhao, T. Jing, Y.F. Li, Q. Ma, X.F. Zhang

    In this paper, we report on the microstructure and magnetocaloric effect in off-stoichiometric LaxFe11.5Si1.5 alloys. The X-ray diffraction and microstructural analysis indicate that the atomic ratio of Fe:Si in the main 1:13 phase is modified by adding excessive La. The off-stoichiometric alloys exhibit lower Curie temperatures and larger thermal hysteresis when comparing with the x = 1.0 alloy. The maximum isothermal entropy change is enhanced by 15% when the excessive La content is x = 1.2. The present study offers an effective and simply way to improve the magnetocaloric effect in such La-Fe-Si alloys.

    更新日期:2017-12-14
  • Effects of N addition on microstructure and mechanical properties of CoCrFeNiMn high entropy alloy produced by mechanical alloying and vacuum hot pressing sintering
    Intermetallics (IF 3.42) Pub Date : 2017-11-20
    Yanchong Xie, Hu Cheng, Qunhua Tang, Wei Chen, Weikun Chen, Pinqiang Dai

    Most of multi-component high entropy alloys (HEAs) are only based on metal elements and rarely added with nonmetallic elements. In present paper, CoCrFeNiMn HEA added with 0.1 at.% N has been successfully synthesized by mechanical alloying (MA) followed by vacuum hot pressing sintering (VHPS). During the MA process, the alloying elements were gradually alloyed and formed as face-center (FCC) solid solutions. Subsequently, σ phases, Cr2N phases, FCC matrix phases with traces of Cr23C6 carbides were observed after VHPS. In comparison with CoCrFeNiMn HEA produced by the same method, the Vickers hardness increased up to 468HV, while the yield stress, ultimate compressive strength increased by 203 MPa and 115 MPa respectively, accompanied by a small decrease in plasticity. This demonstrates that adding N element is a viable approach for properties enhancement of HEAs.

    更新日期:2017-12-14
  • Fabrication of optical gratings through surface patterning of zirconium-based metallic glass by laser irradiation
    Intermetallics (IF 3.42) Pub Date : 2017-11-11
    Rui Yamada, Naoyuki Nomura, Junji Saida, Akira Kawasaki

    Periodic lines with intervals ranging from ∼220 μm down to ∼27 μm were fabricated on the surface of Zr55Cu30Al10Ni5 metallic glass ribbon and disk samples by laser irradiation. The X-ray diffraction results indicated that both oxides (monoclinic ZrO2, tetragonal ZrO2) and crystallites (Cu10Zr7, NiZr2) existed together with the amorphous phase on the surface of the laser-patterned metallic glass samples. The energy-dispersive X-ray spectroscopy of a cross section of a disk sample clearly showed that high amounts of aluminum (292% of the nominal composition) and oxygen were present in the laser-irradiated area, suggesting that Al2O3 formed on the surface of the laser-irradiated region. Reflective diffraction spots were observed from the fine grids with a grating period of ∼27 μm, indicating the excellent periodicity and accuracy of the pattern in two dimensions on the surface of the metallic glass substrates. Calculation of the grating period using Bragg's law confirmed that the spots originated from the periodic patterns of the laser-irradiated lines. Along the lines, pairs of ridges and hollows with a height/depth of ∼0.5 μm were observed; such specific morphology generated the diffraction spots as a reflective grating. We observed structural color gradation from the periodic fine grids under a fluorescent light. The present study showed that it is possible to prepare optical gratings on the surface of metallic glasses by laser irradiation more cheaply and easily than by conventional imprinting.

    更新日期:2017-12-14
  • Investigation on shock-induced reaction characteristics of a Zr-based metallic glass
    Intermetallics (IF 3.42) Pub Date : 2017-11-11
    Chuan Ting Wang, Yong He, Cheng Ji, Yuan He, Wei Han, Xuchao Pan

    The shock-induced reaction behavior of ZrCuNiAl bulk metallic glass (BMG) was investigated by means of a modified quasi-sealed test chamber. A series of quasi-sealed chamber impact experiments were conducted through launching ZrCuNiAl BMG fragments into the test chamber. It was shown that the semi-sphere shape of the modified quasi-sealed chamber suits the expanding manner of reactions. The results demonstrated that the BMG fragments underwent chemical reaction when impacted onto steel target. The energy released by reaction led to significant pressure rise inside the quasi-sealed chamber. It was shown that the amount of energy increased with the increasing of impact velocity. A relationship between the overpressure inside the chamber and the released chemical energy was derived to analyze the effect quantitatively.

    更新日期:2017-12-14
  • A study on the crystallization behavior of amorphous Ti50Ni25Cu25 shape memory ribbon by X-ray diffraction measurement
    Intermetallics (IF 3.42) Pub Date : 2017-11-10
    Chih-Hsuan Chen, Hsin-Kai Wang, Shyi-Kaan Wu

    XRD spectra from the contact and free surfaces of amorphous Ti50Ni25Cu25 ribbon prepared by melt-spinning technique, crystallized, and aged at 500 °C for different times were collected for intensive investigation. A thin layer of textured grains with a thickness of 1 μm formed at the contact surface, having {100}B2 planes parallel to the ribbon surface during the crystallization process and resulting in an extraordinarily strong (200)B2 diffraction peak from the contact surface. This textured layer was caused by the pre-arrangement of atoms with their easy-growth <100>BCC direction parallel to the maximum temperature gradient perpendicular to the contact surface during the melt-spinning process. On the other hand, equiaxed and randomly orientated grains of about 300 ± 100 nm in size formed at the free surface. During the aging process, when aging time exceeded 15 min, precipitation of TiCu along {100}B2 planes significantly distorted the B2 lattice and thus led to broadening, which decreased the intensity of (200)B2 diffraction. Comparisons of experimental results with reported studies show that the texture developed in Ti50Ni25Cu25 ribbon is highly affected by the thickness and cooling rate.

    更新日期:2017-12-14
  • Exploring thermoelectric materials for renewable energy applications: The case of highly mismatched alloys based on AlBi1-xSbx and InBi1-xSbx
    Intermetallics (IF 3.42) Pub Date : 2017-11-08
    Bakhtiar Ul Haq, R. Ahmed, S. AlFaify, Faheem K. Butt, A. Shaari, A. Laref

    The high throughput thermoelectric devices are considered promising futuristic energy source to control global warming and realize the dream of green energy and sustainable environment. The ability of the highly mismatched alloys (HMAs), to show the intriguing impact on the physical properties with controlled modifications, has extended their promise to thermoelectric applications. Here, we examine comprehensively the potential of the two prototypical HMAs such as AlBi1-xSbx and InBi1-xSbx for thermoelectric applications within density functional theory together with the Boltzmann transport theory. For comprehensive understanding, alloying of these materials has been performed over the entire composition range. From our calculations, we found, the replacement of Sb with Bi leads to a significant evolution in the energy band-gap and effective masses of the charge carriers that consequently deliver enhancement in thermoelectric response. Improvement of magnitude 1.25 eV and 0.986 eV has been respectively recorded in band-gaps of AlBi1-xSbx and InBi1-xSbx for the across composition alloying. Similarly, by the electronic-structure engineering of HMAs, thermoelectric properties such as, the Seebeck coefficients over Fermi-level were found to be improved from 82.90 μV/K to 107.52 μV/K for AlBi1-xSbx and 60.32 μV/K to 92.73 μV/K for InBi1-xSbx. As a result, the thermoelectric figure of merit (ZT) and power factor show considerable enhancement as a function of alloying composition for both alloys at room temperature. However, at a higher temperature, the thermal conductivity of these materials experience an exponential increase, results in lower ZT values. Overall, the observed evolution in the electronic structure and thermoelectric response for replacing Sb over Bi is significant in AlBi1-xSbx as compared to InBi1-xSbx. Hence, with the capability of significant and controlled evolution in electronic-structure and subsequent thermoelectric properties, HMAs particularly AlBi1-xSbx are believed potential candidates for thermoelectric applications.

    更新日期:2017-12-14
  • The influence of high-energy ball milling on the heterogeneous reaction kinetics in the Ti-Si system
    Intermetallics (IF 3.42) Pub Date : 2017-11-08
    A.A. Nepapushev, A.S. Rogachev, A.S. Mukasyan

    The high-temperature (1300–1600 K) kinetics for the Ti-Si reactive system were investigated using electro-thermal analysis. The influence of short-term (1–3 min) high-energy ball milling (HEBM) of Ti+0.6Si heterogeneous powder mixtures on the kinetic parameters was also studied. It was shown that HEBM leads to a significant decrease of the apparent activation energy (Ea) of the solid-state reaction between silicon and titanium. For the non-milled mixture, Ea is 339 ± 63 kJ/mol, while after 3 min of HEBM it drops more than twice to 148 ± 12 kJ/mol. The reaction initiation temperature also decreases with an increase of HEBM time: from 1467 ± 62 K for the pristine mixture to 1110 ± 42 K after 3 min of mechanical treatment. The conclusion was made that a decrease of crystalline size and an increase of the crystal lattice defect concentration, which in combination enhance the grain boundary diffusion, can be responsible for the high reactivity of the mechanically activated mixtures.

    更新日期:2017-12-14
  • Cryogenic mechanical property and deformation behavior of a Ti-based metallic glass matrix composite by three point bending tests
    Intermetallics (IF 3.42) Pub Date : 2017-11-08
    Y.S. Wang, S.B. Gao, L. Zhang, W.L. Yuan, G.J. Hao, J.P. Lin

    In this paper, cryogenic mechanical property and deformation behavior of a Ti-based metallic glass matrix composites (MGMCs) containing the in-situ β dendrite phase were investigated by three point bending tests from 298 K to 77 K. The result demonstrated that the flexural strength increased with the decreasing applied temperature, e.g. the flexural yielding strength increased by 32.6% from 1890 MPa at 298 K to 2506 MPa at 77 K, which has been fitted as an exponential function on the basis of the modified Zerilli and Armstrong (Z–A) model. It is found that the β dendrite phase lost its activity gradually and failed to promote shear-bands multiplication with decreasing testing temperature, leading to plasticity of the MGMC decreased. The deformation mechanism was discussed according to the fracture characteristics of the composite deformed at different cryogenic temperature.

    更新日期:2017-12-14
  • Thermogravimetric investigation on oxidation kinetics of complex Ti-Al alloys
    Intermetallics (IF 3.42) Pub Date : 2017-11-07
    Oxana Ostrovskaya, Claudio Badini, Giorgio Baudana, Elisa Padovano, Sara Biamino

    The oxidation resistance in air of Ti-48Al-2Cr-2Nb, Ti-48Al-2Nb-0.7Cr-0.3Si, Ti-43.5Al-4Nb-1Mo and Ti-47Al-2Cr-8Nb alloys was investigated in the range of 800–1000 °C. Specimens were machined from the core of bars processed by Electron Beam Melting. Oxidation tests were performed in TGA equipment under isothermal conditions at different temperatures. The composition of the oxide layers was investigated by XRD, SEM-EDS and XPS. Layer exfoliation was observed, starting from different temperatures for the different alloys. When spallation did not happen in a significant extent the oxide layers grew according to a parabolic law. The kinetic rate constants and the activation energies were calculated. These kinetic parameters allowed to assess a rank of oxidation resistance, which can be correlated with the composition of the alloys.

    更新日期:2017-12-14
  • Invar effect of Fe-based bulk metallic glasses
    Intermetallics (IF 3.42) Pub Date : 2017-11-06
    Q. Hu, J.M. Wang, Y.H. Yan, S. Guo, S.S. Chen, D.P. Lu, J.Z. Zou, X.R. Zeng

    Invar alloys have a wide application owing to its low expansion characteristics. Recently, it is revealed that some Fe-based bulk metallic glasses (BMGs), which have much higher strength than that of traditional Fe-Ni Invar alloys, also have the Invar effect. Combining the low expansion of the Invar effect and the good mechanical properties of Fe-based BMGs has an attractive potential for applications, for which firstly systematic study on the Invar effect of Fe-based BMGs is needed. In this work, the thermal expansion of 14 FeSiPCBM, (Fe,Co)BSiNb, FeNiPC and FeMoPCB BMGs are investigated. The results show all the alloys have the Invar effect, but can be categorized in two types, depending on whether the low expansion occurs in a wide temperature range below the Curie temperature Tc, or in a narrow temperature range near Tc. It is found the former type of alloys have lower Tc and saturation magnetic induction density, i.e., weaker magnetic properties. The substitution of Fe by Co and Ni weakens the Invar effect. These findings are explained based on the characteristics of the amorphous structure and the Bethe-Slater curve. The findings in this paper help to further develop low expansion Fe-based BMGs.

    更新日期:2017-12-14
  • AlSb intermetallic semiconductor compound formation by solid state reaction after partial amorphization induced by mechanical alloying
    Intermetallics (IF 3.42) Pub Date : 2017-11-06
    Florin Popa, Ionel Chicinas, Olivier Isnard

    The formation of AlSb intermetallic semiconductor by solid state reaction has been studied as a function of milling time. As revealed by X-ray diffraction study, the formation reaction is a complex phase change, involving successively crystalline, amorphous and crystalline and finally crystalline state. The amount of amorphous phase was quantified. Depending on milling time, a disorder parameter was computed and its role on AlSb formation is discussed. Upon milling time, short-range order was evidenced and distance characteristic of AlAl and AlSb pairs was evidenced. Morphological evolution during the formation process is presented. Semiconductor behavior was evidenced by electrical resistivity measurements and the conduction activation energy was computed.

    更新日期:2017-12-14
  • Achieving high power factor of p-type BiSbTe thermoelectric materials via adjusting hot-pressing temperature
    Intermetallics (IF 3.42) Pub Date : 2017-11-03
    Xiaocui Wang, Yuanyue Li, Guoxia Liu, Fukai Shan

    Achieving high power factor values for BiSbTe alloys is important for further elevation of their thermoelectric performance. In this report, Bi0.4Sb1.6Te3 bulk samples were prepared by a fusion method followed by hot pressing at different temperatures (523 K, 573 K, 623 K and 663 K), and their thermoelectric properties were investigated from 300 K to 500 K. It was found that the power factor and thermal conductivity increased significantly with increasing hot-pressing temperature. A record power factor of 53.8 μW/(cm K2) at 300 K was achieved for the sample hot pressed at 663 K. In addition, a maximum ZT of 1.3 at 413 K and average ZTave of 1.2 at 300–500 K were achieved for the sample hot pressed at 623 K.

    更新日期:2017-12-14
  • Review of porous intermetallic compounds by reactive synthesis of elemental powders
    Intermetallics (IF 3.42) Pub Date : 2017-11-01
    Yao Jiang, Yuehui He, C.T. Liu

    Porous intermetallic compounds fabricated by reactive synthesis of elemental powders exhibit good pore formation capability and unique properties integrating the advantages of both metals and ceramics. The following aspects for the reactively synthesized porous intermetallics are reviewed: (1) near-net shaping fabrication process of porous intermetallics through an elemental powder mixture, (2) theoretical basis of the reactive synthesis procedure, (3) the pore structure properties and their quantitative relations, (4) the material properties including the mechanical property, acid and alkali corrosion resistivity, high temperature oxidation and sulfuration resistance, machinability, weldability, thermal shock resistance, hydrogen evolution activity, etc. and (5) applications of porous intermetallics in industrial filtration fields.

    更新日期:2017-12-14
  • Magnetic properties and large magnetic entropy change in rare earth-rich cadmium compounds of RE4CoCd (RE = Tm and Ho)
    Intermetallics (IF 3.42) Pub Date : 2017-10-31
    Lingwei Li, Dexuan Huo, Kunpeng Su, Rainer Pöttgen

    The magnetic properties and the magneto-caloric effect (MCE) of the cadmium compounds Tm4CoCd and Ho4CoCd with cubic Gd4RhIn-type structure were studied. A second order magnetic phase transition from a paramagnetic (PM) to a ferromagnetic (FM) state at around the Curie temperatures of TC ∼ 4.5 and 22 K together with a large reversible MCE for Tm4CoCd and Ho4CoCd were observed, respectively. For a field change of 0–70 kOe, the values of maximum magnetic entropy change (−ΔSMmax), relative cooling power (RCP) and refrigerant capacity (RC) were evaluated to be 19.2 J/kg K, 434 J/kg and 342 J/kg for Tm4CoCd, and 18.1 J/kg K, 807 J/kg and 635 J/kg for Ho4CoCd, respectively.

    更新日期:2017-12-14
  • First-principles and Monte Carlo studies of the Fe2NiZ compounds on exchange interactions and Curie temperatures
    Intermetallics (IF 3.42) Pub Date : 2017-10-31
    Xiao-Ping Wei, You-He Zhou

    Using the spin-polarized relativistic Korringa-Kohn-Rostoker in combination with Monte Carlo calculations, we study the exchange interactions and Curie temperatures of Fe2NiZ (Z = Al, Ga, In, Si, Ge, Sn, P, As, Sb) compounds with the Hg2CuTi structure. Results show that the inter-sublattice Fe(A)-Fe(B) exchange plays a dominant role in interactions, and provide a major contribution to the Curie temperature. In the same period, the inter-sublattices Fe(A)-Fe(B) along with Fe(B)-Ni(C) and Fe(A)-Ni(C) interactions decrease when changing Z from III to V group. In contrast, the intra-sublattice Fe(B)-Fe(B) exchange exhibits an upward tendency, and the intra-sublattice Ni(C)-Ni(C) interaction almost closes to zero in all cases. Further, the Curie temperature is estimated based on the Heisenberg exchange coupling parameters between the constituents. The calculated Curie temperatures noticeably higher than the room temperature indicate these compounds more favorable in realistic spintronics application. In addition, the Monte Carlo method is adopted to obtain more accurate Curie temperatures by modeling the normalized magnetization as functions of the temperature, our results are in good accordance with available experimental values.

    更新日期:2017-12-14
  • Exceptionally high nanoscale wear resistance of a Cu47Zr45Al8 metallic glass with native and artificially grown oxide
    Intermetallics (IF 3.42) Pub Date : 2017-10-31
    D.V. Louzguine-Luzgin, M. Ito, S.V. Ketov, A.S. Trifonov, J. Jiang, C.L. Chen, K. Nakajima

    The atomic-scale and nanoscale scratch wear resistance of a Cu47Zr45Al8 bulk metallic glass is studied in the present work using an atomic force microscopy focusing on the role of surface oxide and thermally induced changes in the glassy matrix. The wear rate is found to be significantly reduced and the wear resistance drastically improved by the formation of native and artificially grown surface oxides. This finding makes the studied alloy a very promising candidate for application as a wear resistant part in a micro-electro-mechanical device.

    更新日期:2017-12-14
  • Atomic structure, stability and electronic properties of S(Al2CuMg)/Al interface: A first-principles study
    Intermetallics (IF 3.42) Pub Date : 2017-10-26
    Xingzhi Pang, Wenchao Yang, Jianbing Yang, Mingjun Pang, Yongzhong Zhan

    Interfacial models of Al2CuMg/Al were investigated by first-principles calculations based on density functional theory. Two types of Al2CuMg(001)/Al(021) interface structures were investigated in consideration of two different terminations for Al2CuMg(001) surface (Al-terminated and CuMg-terminated). The interaction of interfaces was analyzed by the optimized atomic structures. The ideal work of adhesion (Wad) of the Al2CuMg(001)/Al(021) interfaces was also calculated. The results show that the interface model with CuMg-terminated is more stable than that of Al-terminated. It is also demonstrated from the values of interfacial energy (γint) that the CuMg-terminated interface is more thermodynamically stable. The calculated electronic properties, including charge density distribution and density of states, reveal that there is a significant hybridization among the interfacial Cu 3d, Mg 3p and Al 3p states. It is the main reason why CuMg-terminated interface is more stable.

    更新日期:2017-12-14
  • Effects of thermal annealing on microstructure and magnetic properties of electrodeposited Co-Fe alloys
    Intermetallics (IF 3.42) Pub Date : 2017-10-24
    Thanakrit Chotibhawaris, Tachai Luangvaranunt, Pongsakorn Jantaratana, Yuttanant Boonyongmaneerat

    Thermal annealing could potentially serve as important instrument for controlling and improving the properties of the soft magnetic films. A systematic investigation is carried out in this study to determine and analyze the effects of low-temperature heat treatment on the microstructure and magnetic properties of CoFe films of different chemical compositions. The coercivity of the alloys is found to be critically influenced by surface roughness and uniaxial anisotropy, which is in turn affected by thermal annealing. The saturation magnetization on the other hand is controlled mainly by chemical compositions.

    更新日期:2017-12-14
  • Modeling of the temperature-dependent ideal shear strength of solid single crystals
    Intermetallics (IF 3.42) Pub Date : 2017-10-23
    Tianbao Cheng, Daining Fang, Yazheng Yang

    Knowledge of the ideal shear strength of solid single crystals at finite temperatures is of fundamental importance. It is mainly determined by the molecular dynamics simulations. However, thus obtained results are strongly dependent on the employed empirical potentials. In the present work, two theoretical models for the temperature-dependent ideal shear strength of single crystals are established based on the Frenkel's classical theory and the energy view. To test the established models, the ideal shear strengths of β-NiAl and γ-Ni3Al alloys are calculated from 0 K to the melting point and compared with the results reported in the literature. The study shows that both shear modulus and ideal shear strength firstly remain approximately constant and then decrease almost linearly as temperature changes from 0 K to melting point. However, the ideal shear strength has stronger temperature dependence than the shear modulus.

    更新日期:2017-12-14
  • Effect of notch depth on the mechanical behavior of Cu50Zr50 metallic glasses revealed by molecular dynamics simulations
    Intermetallics (IF 3.42) Pub Date : 2017-10-21
    G.J. Yang, B. Xu, C. Qi, L.T. Kong, J.F. Li

    Metallic glasses (MGs) with various geometrical notches have been one of the most attractive research topics because of their interesting mechanical behavior. In this work, molecular dynamics simulations were employed to examine the effect of internal notch depth on the mechanical behavior of Cu50Zr50 MGs. It is shown that both the strength and the deformation mode are sensitive to the notch depth, and in particular to the inter-void ligament distance. With increasing the notch depth, the notch intensification gets enhanced, while the deformation mode is seen to change from shear banding dominated to mixed mode and then to necking governed. Detailed stress distribution analysis reveals that the notch intensification and the deformation mode transition result from the stress state change induced by the presence of notches. The critical effective shear stress corresponding to local/atomic yielding in the MGs is identified to be around 1.9 GPa. In addition, the intrinsic size confinement effect also influences the deformation process. The findings are expected to provide useful guidance for materials design and investigation of yielding in MGs based on atomistic simulations.

    更新日期:2017-12-14
  • Correlations between the wear resistance and properties of bulk metallic glasses
    Intermetallics (IF 3.42) Pub Date : 2017-10-20
    Zhenlong Liao, Nengbin Hua, Wenzhe Chen, Youting Huang, Tao Zhang

    The wear, elastic, mechanical and thermodynamic properties of bulk metallic glasses (BMGs) is studied to explore correlations between the wear resistance and properties of BMGs. It is found that the wear resistance of BMGs is dominated by synergistic effects of strength factors, namely the hardness (H), Young's modulus (E), yield strength (σy) and glass transition temperature (Tg), as well as toughness factors, like the notch toughness (KQ) and Poisson's ratio (ν). Moreover, a novel strategy for optimizing the wear resistance of BMGs is proposed from elastic perspective. The wear resistance of BMGs is correlated with chemistry-induced changes to bulk modulus (B) and Poisson's ratio (ν) for the first time. Developing BMGs with high value of B 0.5 · [ 2 ( 1 + v ) / 3 ( 1 − 2 v ) ] 0.25 can achieve simultaneously both high strength and good toughness, which provides the elastic opportunities for designing ultra-wear-resistant BMGs.

    更新日期:2017-12-14
  • Stacking fault energy of face-centered-cubic high entropy alloys
    Intermetallics (IF 3.42) Pub Date : 2017-10-16
    S.F. Liu, Y. Wu, H.T. Wang, J.Y. He, J.B. Liu, C.X. Chen, X.J. Liu, H. Wang, Z.P. Lu

    The stacking fault energy (SFE) values of several typical face-centered-cubic (fcc) high-entropy alloys (HEAs) were experimentally measured by weak-beam dark-field transmission electron microscopy. It was found that the SFE of the Fe-Co-Ni-Cr-Mn HEA system strongly depends on the SFE of the individual constituents. Specifically, the SFE of this HEA system is closely associated with the Ni concentration in the alloys. Additionally, the lower SFE tends to promote formation of more deformation twins with a smaller thickness under loading, leading to better mechanical properties, especially at low temperatures.

    更新日期:2017-12-14
  • Influence of Fe-doping on magnetic structure and martensitic transformation in NiMnIn and NiMnSb alloys
    Intermetallics (IF 3.42) Pub Date : 2017-10-16
    Yuexing Ma, Hongyue Hao, Xiaotong Liu, Hongzhi Luo, Fanbin Meng, Heyan Liu

    Influence of Fe substitution for Ni on the magnetic properties and martensitic transformation was investigated theoretically in Heusler alloys Ni2Mn1.5Z0.5 (Z = In, Sb). Fe-doping does not change the general magnetic structure of Ni2Mn1.5Z0.5. In both Ni2Mn15In0.5 and Ni1.75Fe0.25Mn1.5In0.5 the austenitic phase is ferromagnetic and martensitic phase is antiferromagnetic, which leads to the large ΔM observed experimentally. But in Ni2Mn1.5Sb0.5 and Ni1.75Fe0.25Mn1.5Sb0.5, the antiferromagnetic state is stable in both austenite and martensite. This difference is mainly related to the different atomic radii of In and Sb, which change the distance between Mn (B) and Mn (D). Parallel or antiparallel coupled Mn moments determine the magnetic properties of these alloys. But the partial moment of Fe is large and its direction reverses after martensitic transformation, which makes it a possible way to adjust the magnetic properties of MSMAs. Calculation also suggests that the substitution of Fe for Ni can lower the martensitic transition driving force and lead to the decrease of phase transition temperature. These results agree well with preceding experimental results and make reasonable explanation for them.

    更新日期:2017-12-14
  • Effect of the stress ratio on the fatigue behavior of Zr55Al10Ni5Cu30 bulk metallic glass. Part II — Reconfirmations and new findings on the crack propagation mechanism
    Intermetallics (IF 3.42) Pub Date : 2017-10-16
    Benjamin Guennec, Takuya Nobori, Hirotaka Kuwahara, Akira Ueno

    The assessment of the reliability of Bulk Metallic Glasses (BMGs) as structural materials needs further investigations, particularly dealing with the impact of the loading condition on the fatigue behavior. Stress ratio R is one of these important parameters associated with the fatigue loading. The present work investigates the high-cycle fatigue properties of Zr55Al10Ni5Cu30 BMG at three distinct stress ratios from 0.1 to 0.7. Even though Part I of the present study has been mainly focused on the fatigue resistance considerations, a peculiar feature was found on the fracture surface at stress ratio of R = 0.7. Thus, this second part is investigating the fatigue crack propagation behavior of Zr55Al10Ni5Cu30 BMG. Experimental results highlight a crack propagation behavior at R = 0.1 and 0.4 similar to the results reported in the research field. On the other hand, observations of fracture surface and tensile surface of specimens failed at high stress ratio of R = 0.7 underline a peculiar crack propagation behavior.

    更新日期:2017-12-14
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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