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Journal of Alloys and Compounds
Elsevier Science S.A.
Journal of Alloys and Compounds

Elsevier Science S.A.

0925-8388

Journal of Alloys and Compounds/Journal Journal of Alloys and CompoundsSCIISTPEI
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    Densification and microstructure formation mechanisms of 80 W-14Ni-6Fe fabricated by laser powder bed fusion

    Ye H.Huang Y.Wei C.Liu Y....
    12页
    查看更多>>摘要:? 2022 Elsevier B.V.Tungsten heavy alloys (WHAs) are typically refractory alloy, and machining tungsten alloy components at room temperature is a challenge. Currently, Laser additive manufacturing (LAM) provides a feasible route for machining complex tungsten alloy parts. In this study, the high relative density and almost defect-free 80 W-14Ni-6Fe specimens were successfully obtained via using laser powder bed fusion (LPBF). The densification, microstructure formation mechanisms and tensile properties of LPBFed tungsten alloy were systematically investigated. The results revealed that the relative density of tungsten alloy increases and then decreases with the laser energy density increases. Nearly full densification 80 W-Ni-Fe alloys were obtained when the volumetric energy density (VED) was 80–100 J/mm3. The typical microstructure contained irregular tungsten grain consolidation, W dendrites, spherical tungsten particles and Ni-Fe bonding phase, which was due to melting of partial tungsten particles during LPBF. Interestingly, many ultra-fine crystals occurred in the Ni-Fe matrix, which was closely related to the rapid heat and cooling during LPBF. Besides, there were two strengthening mechanisms in LPBFed 80 W alloy, respectively solid solution strengthening and dispersion strengthening. Hence, the 80 W-Ni-Fe alloy with optimum process parameters exhibited high tensile strength, and the ultimate tensile strength (UTS) reached 1064MP. This work will aid in the additive manufacturing of refractory metal alloys with excellent properties and expand the application prospects of tungsten alloys.

    The nucleation mechanism of martensite and its interaction with dislocation dipoles in dual-phase high-entropy alloys

    Wang P.Song Z.Lin Y.Li Q....
    9页
    查看更多>>摘要:? 2022 Elsevier B.V.The recent progresses in experiments have proven that the recently synthesized dual-phase high-entropy alloys (DP-HEAs) exhibit ultrahigh ductility without sacrificing the high strengthen. However, the original atomic mechanisms of the martensitic transformation process and its interaction with dislocations remain mysterious. In this work, the nucleation mechanisms of martensite are thoroughly investigated with various arrangement of dislocation dipoles via molecular dynamics (MD) simulations. Both stress-induced and thermal-induced martensitic transformation are reproduced in our simulations, which obeys the Burgers orientation relationship. Under the thermal fluctuation, the nucleation of martensite is controlled by the localized stress levels and strain energies. The thermal-induced martensite is found to nucleate near the dislocation dipoles once the strain energy reaches the required value. Upon loading, the fast-moving stress-induced martensite bends and wraps the dislocation dipoles in propagation path. These results provide a fundamental understanding of the martensitic nucleation in DP-HEA and its strengthening and toughening mechanisms, contributing benefits to design new alloys.

    The effect of sc addition on microstructure and mechanical properties of as-cast Zr-containing Al-Cu alloys

    Qin J.Tan P.Quan X.Liu Z....
    10页
    查看更多>>摘要:? 2022 Elsevier B.V.In this paper, the effect of Sc alloying on the microstructure and mechanical properties of as-cast Zr-containing Al-Cu alloys is investigated by microstructure characterization, thermal analysis and first-principles calculations, and the related mechanisms is discussed. The results show that when the Sc content is 0.3%, the grains and Al2Cu eutectic structure in the alloy can achieve the best refining effect. The strength and plasticity of the alloy are synergistically improved, and its ultimate tensile strength, yield strength and elongation are 211.3 MPa, 310.6 MPa and 6.3%, which are 43.5%, 35.1% and 50.0% larger than that of the base alloy (without Sc addition), respectively. When the Sc content is increased to 0.4%, the grain refinement is limited. This is because Al3(Sc,Zr) is coagulated, and the Al/Al3Sc interfacial energy is higher under Sc-rich conditions and the nucleation ability is poor. According to the calculation results of interfacial energy, the order of heteronucleation ability of α-Al is Al3(Sc,Zr)> Al3Zr> Al3Sc. And it is accompanied by a decrease in mechanical properties, which is because cracks are easily formed at the connection between the coarse W phase and the matrix, and stress concentration is easily caused during the deformation process. Furthermore, the solidification paths of alloys with different Sc contents are predicted by thermal calculation. When the Sc content is 0.3%, the alloy will generate metastable Al3(Sc,Zr) and stable Al3Sc during solidification. And the distribution of petal-like dispersoids is observed as linear clusters and blocky clusters in the experiment.

    Effect of rare earth doping on electronic and gas-sensing properties of SnO2 nanostructures

    Xu H.Li J.Li P.Shi J....
    11页
    查看更多>>摘要:? 2022 Elsevier B.V.Tin dioxide (SnO2) and rare earth (Y, La, Pr, Tb, and Er)-doped SnO2 materials were synthesized by a solvothermal method and used for gas sensors. The effect of rare-earth (RE) doping on structural, electronic, and gas-sensing properties of SnO2 has been investigated. According to a comparative study on the gas-sensing properties of SnO2 and RE-doped SnO2 gas sensors to various testing gases, the RE-doped SnO2 sensors showed enhanced sensitivities to different testing gases. Especially, the Pr-doped SnO2 sensor exhibited outstanding sensing properties to SO2, including a high response of 19.5–50 ppm SO2, excellent selectivity, repaid response and recovery rates, and superior long-term stability. According to the structural analyses, DFT calculation, and the electrochemical measurement of the SnO2 and Pr-SnO2 materials, the improved electron excitation efficiency endowed the Pr-SnO2 with a high density of free electrons that can be trapped by atmospheric oxygen species and participated in SO2-sensing reactions. Moreover, after the Pr doping of SnO2, the enhanced charge carrier transport properties, including prolonged electron lifetime, improved electron diffusion coefficient, and increased effective diffusion length, were conducive to improving the SO2-sensing property.

    Boride evolutionary behavior and mechanism in the TLP repaired IN738 superalloy with crack-like defects

    Zhang H.Xue J.Guo W.Ye Y....
    11页
    查看更多>>摘要:? 2022 Elsevier B.V.Boride evolution in the transient liquid phase (TLP) repaired cracks for IN738LC alloy had important influence on mechanical properties. The microstructure of the repaired crack contained two typical zones: isothermal solidification zone (ISZ) and diffusion affected zone (DAZ). There were blocky and acicular borides with hexagonal crystal structure in the DAZ, and boride morphology depended on the interfacial distance, Cr/B content, and aging time. i) As the distance from the ISZ/DAZ interface increased, blocky borides gradually decreased and acicular borides began to form. ii) When Cr and B were sufficient, blocky borides firstly formed. When the content decreased to a certain extent, borides would not form. iii) As aging time increased, the amount of blocky borides gradually increased due to the diffusion of B. Meanwhile, acicular borides began to form along (111) plane, which could effectively reduce the interfacial energy.

    Hydrothermal synthesis and their ethanol gas sensing performance of 3-dimensional hierarchical nano Pt/SnO2

    Fan H.Zheng X.Shen Q.Wang W....
    8页
    查看更多>>摘要:? 2022 Elsevier B.V.A hierarchical SnO2 nanosheet structure was constructed by the hydrothermal method using hydrated stannous chloride and thiourea as raw materials. Then lysine was used as a coupling agent to load Pt nano quantum dots with different contents on the surface of the SnO2 nanosheets. The composition, morphology and structure of Pt/SnO2 were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy dispersive spectroscopy. The gas sensitivity of the Pt/SnO2 and SnO2 nanostructures were also studied in detail. Compared with the pure SnO2 nanosheets, the 3-dimensional structured nano 2.0% Pt/SnO2 (Pt: SnO2 = 2.0%, wt%) exhibits a higher gas sensitivity to ethanol gas at 240 °C. The gas sensitivity to 100 ppm ethanol of hierarchical nano 2.0% Pt/SnO is 2.5 times higher than pure SnO2 nanosheet, and the response time and recovery time are 4 s and 5 s, showing excellent response and recovery behavior. Meanwhile, the sensor also exhibits a lower detection limit of 0.272 ppm, as well as the excellent temperature and time stability. The higher gas sensitivity is contributed from the “spillover” effect of Pt nano quantum dots and the Schottky barrier at the heterojunctions of hierarchical Pt/SnO2 nanostructures.

    Hydroxyapatite/chitosan-metformin composite coating enhances the biocompatibility and osteogenic activity of AZ31 magnesium alloy

    Li H.Shen C.Qin Z.Wei H....
    11页
    查看更多>>摘要:? 2022 Elsevier B.V.The rapid degradation rate of degradable magnesium alloys limits their application as orthopaedic implants. To improve the osteogenic activity and corrosion resistance of magnesium alloys, a hydroxyapatite/chitosan-metformin (HA/CS-MF) composite coating was prepared on AZ31 magnesium alloy by hydrothermal treatment. The structure and morphology of the composite coating were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). Electrochemical tests and hydrogen evolution experiments were carried out to evaluate the corrosion resistance of the HA/CS-MF composite coating. At the same time, the cytocompatibility, osseointegration ability and anti-inflammatory activity of the HA/CS-MF composite coating were studied. The findings revealed that the HA/CS-MF composite coating exhibits excellent corrosion resistance, biocompatibility and osteogenic activity; can upregulate the expression level of bone-related genes; and is conducive to the polarization of M2 macrophages.

    Heat capacity and thermodynamic properties of PbS: Optimization based on calorimetric and electrochemical data

    Osadchii V.O.Osadchii E.G.Gurevich V.M.Polyakov V.B....
    12页
    查看更多>>摘要:? 2022 Elsevier B.V.Heat capacity of PbS (galena) has been measured in the temperature range from 12 to 338 K using adiabatic calorimetry. Results of the measurements are consistent with previous adiabatic calorimetric data measurements but differ notably from those obtained by relaxation calorimetry. Using experimental data on adiabatic heat capacity measurements in the range of 12–338 K (including our data), results of EMF measurements, and literature data on H0(T) – H0(298.15 K) as inputs, we have optimized the thermodynamic properties of lead sulfide (PbS, galena) based on the quasi-harmonic model vibrational spectrum proposed by Kieffer and advanced to consider intrinsic anharmonicity. In this approach, the volume and temperature dependence of vibrational frequencies are considered, and the enthalpy of formation of PbS, ΔfH0(298.15 K), is treated as an optimized model parameter. The thermodynamic properties of PbS are described with a single set of model parameters over the entire range of its stability (0–1374 K) at a pressure of 1 bar. The model can be optimized based on either the reduced (Cp0 and ΔfG0(T)) or full (Cp0, H0(T) – H0(298.15 K), ΔfG0(T)) datasets. The both variants of the optimization predict the similar thermodynamic properties of PbS, in particular, values of the enthalpies of formation differ less than 0.1 kJ mol?1 and are consistent with ΔfH0(298.15 K) obtained experimentally by oxide melt solution calorimetry. The low-temperature adiabatic calorimetry data and high-temperature results of EMF experiments (or other reliable experimental data on ΔfG0(T)) represent a minimal sufficient set of input data providing optimization of thermodynamic properties at ambient pressure by the technique established in present study.

    Effective metal encapsulation of carbon nanotubes by micro-current electrochemical deposition

    Fu C.Yang N.Huang H.Bu F....
    7页
    查看更多>>摘要:? 2022 Elsevier B.V.The inner cavities of carbon nanotubes (CNTs) have attracted much attention for one-dimensional structures and their unique properties. The encapsulation of hetero-structures into CNTs is the foundation for potential applications. Solution and vapor methods have been well adopted for CNTs encapsulations. The solution method is restricted to its low encapsulation yield. Only chemicals with relatively low sublimation points under low pressures and low activity have been demonstrated to be encapsulated into the inner cavities of CNTs by vapor methods. No effective encapsulation method for most metals has been explored so far. Now, a widely applicable metal encapsulation method, micro-current electrochemical deposition, has been demonstrated to encapsulate lithium, sodium and potassium metals into CNTs with high yield. The volumetric encapsulation yields of lithium, sodium and potassium metal have been demonstrated to be higher than 65%.

    Vacuum diffusion bonding of TC4 titanium alloy to 316L stainless steel with AlCoCrCuNi2 high-entropy alloy interlayer

    Li P.Li C.Dong H.Wu B....
    15页
    查看更多>>摘要:? 2022 Elsevier B.V.A newly designed AlCoCrCuNi2 high-entropy alloy (HEA) interlayer was used for vacuum diffusion bonding of TC4 titanium alloy (TC4) to 316L stainless steel (316L). The sluggish diffusion effect suppressed the formation and growth of intermetallic compounds (IMCs). The effect of bonding temperature on the microstructure evaluation, the elemental diffusion behavior and mechanical property of the joint was investigated. The HEA interlayer and 316L substrate present a reliable metallurgical combination, and solid solution zone was formed at the HEA/316L interfacial diffusion zone. The typical microstructure of the TC4/HEA diffusion zone was composed of α + β-Ti/Ti2Ni/Ti(Co, Ni)/Al(Co, Ni)2Ti+Cr-rich phase/discontinuous precipitation zone/HEA interlayer. The diffusion zone near the B2 phase presented a lower growth activation energy than that near the FCC phase on the 316L side. As the bonding temperature increased from 860 °C to 1010 °C, the interface of TC4/Ti2Ni changed from straight to serrated structure, which prevented the crack propagation and enhanced the mechanical properties of the joint. The maximum shear strength of 214 MPa was obtained at the bonding temperature of 1010 °C.