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Intermetallics
Elsevier Science
Intermetallics

Elsevier Science

0966-9795

Intermetallics/Journal IntermetallicsSCIISTPEI
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    Structural evolution and improvement of magnetic properties of hot-deformed CeFeB magnets with Nd70Cu30 addition

    Li X.Jiang Q.-Z.Rehman S.U.Huang Q.-F....
    9页
    查看更多>>摘要：? 2022 Elsevier LtdThe low magnetic properties of Ce-based magnets limit their application. In this paper, we aim to improve the coercivity, remanence and maximum energy product of hot-deformed CeFeB magnets by adding low melting Nd70Cu30 alloy. It is found that the addition of Nd70Cu30 remarkably improve the thermal stability and magnetic properties of Ce–Fe–B-based hot-deformed magnets. It is shown by analyzing the microstructure that the proportion of the coarse grain region decreases and the proportion of the liquid region increases in the magnet after adding Nd70Cu30 alloy. The former reduces the nucleation sites of magnetization reversal and the latter weakens the intergranular exchange coupling. Furthermore, the typical core-shell structure was found to be formed in magnets. TEM observation demonstrated that Nd, Ce and Cu were enriched at grain boundaries. Two Curie temperatures were obtained due to different types of 2:14:1 phase, i.e. the incipient CeFeB phase and the newly formed (Nd, Ce)2Fe14B hard magnetic phase. Because of the combined effect of (Nd, Ce)2Fe14B phase and intercrystalline phase, the comprehensive magnetic properties of hot-deformed Ce–Fe–B-based magnets with Nd70Cu30 addition are greatly improved.
      原文链接:
    • NSTL
    • Elsevier

    Microstructure and mechanical property of novel NiAl-based hypoeutectic/eutectic/hypereutectic high-entropy alloy

    Wang L.Su Y.Yao C.Huang Y....
    15页
    查看更多>>摘要：? 2022 Elsevier LtdIn this paper, we investigate the microstructures and mechanical properties of novel NiAl-MoxCrxVx, NiAl-MoyCryFey and NiAl-MozCrzVzFez eutectic high-entropy alloy (EHEA) systems. The microstructures of three alloy systems change from hypoeutectic (primary NiAl + eutectic, x = 7.5,8.33/y = 13.33,14.0/z = 9.0,9.5, hypo-EHEA) to eutectic (x = 8.7/y = 14.5/z = 10.0, EHEA) and then to hypereutectic (primary MoCrV/MoCrFe/MoCrVFe + eutectic, x = 9.0,10.0/y = 15.0,16.0/z = 10.5,11.0, hyper-EHEA). The microhardness of primary MoCrV/MoCrFe/MoCrVFe is higher than that of primary NiAl. It almost has a rule that the yield strength gradually increases from hypo-EHEA to EHEA, and then to hyper-EHEA, which is attributed to a certain amount of high-microhardness primary MoCrV/MoCrFe/MoCrVFe phase in hyper-EHEA. For the EHEAs, the microstructures of NiAl–Mo8.7Cr8.7V8.7/NiAl–Mo14.5Cr14.5Fe14.5/NiAl–Mo10Cr10V10Fe10 are composed of eutectic cells or eutectic dendrites which consist of NiAl (B2) and MoCrV/MoCrFe/MoCrVFe (BCC) lamellar phases, respectively. It is also found that the plenty of fine (Ni,Al)-rich precipitates occur in MoCrFe and MoCrVFe phases (SEM images). Moreover, according to the phase composition, it is determined that MoCrV/MoCrFe/MoCrVFe is a high entropy phase, thus possessing a better strengthening effect on NiAl. Correspondingly, three EHEAs possess the good mechanical properties, and the microhardness and the yield strength exhibit an increased trend: NiAl–Mo8.7Cr8.7V8.7 < NiAl–Mo14.5Cr14.5Fe14.5 < NiAl–Mo10Cr10V10Fe10 EHEAs. The major strengthening mechanisms are the solution strengthening and the precipitation strengthening.
      原文链接:
    • NSTL
    • Elsevier

    Phase transformations and phase stability in the Ti–44 at.%Al–(0–7 at.%)Mo system

    Musi M.Clemens H.Spoerk-Erdely P.Stark A....
    9页
    查看更多>>摘要：? 2022 The AuthorsMolybdenum is an excellent candidate to study the effect of β-stabilizing elements on the phase transitions in intermetallic γ-TiAl based alloys. In the present work, two model alloys based on the Ti–44Al (at.%) system containing 1 at.% and 5 at.% Mo are investigated. Examinations of the microstructures after casting and subsequent heat treatments reveal significant differences in the morphology and amount of the phases present and, thus, highlight the effect of Mo on the different phase transformations near and far from thermodynamic equilibrium. In-situ high-energy X-ray diffraction and differential scanning calorimetry were employed to identify the occurring phases and determine the phase transition temperatures in the two model alloys. Especially, the β phase was found to be strongly impacted by the Mo content of the alloys. While the β phase is only present at high temperatures in the Ti–44Al–1Mo alloy, it is thermodynamically stable from the liquidus temperature downwards to room temperature in the Ti–44Al–5Mo alloy. Long-term heat treatments for 30 days at 1000 °C were conducted to determine the phase equilibria at intermediate temperatures. Ultimately, the findings of this work were combined with data from literature to reassess the quasi-binary Ti–44Al–(0–7)Mo (at.%) phase diagram.
      原文链接:
    • NSTL
    • Elsevier

    Effect of W on the thermal stability, mechanical properties and corrosion resistance of Fe-based bulk metallic glass

    Zhang X.Lai L.Xiao S.Zhang H....
    10页
    查看更多>>摘要：? 2022 Elsevier LtdIn this work, the effect of refractory metal W on the thermal stability, mechanical properties and corrosion resistance of Fe36Cr23Mo18-XWXC15B6Y2 (X = 0, 3, 5, 8, 10, 12, 15, 18) bulk metallic glasses (BMGs) were systematically investigated. The results showed that a wide composition range could be quenched to form BMG when the considerable refractory metal was introduced, although the higher mixing enthalpy of W than Mo between other elements (such as Fe, Cr, C) incited the deterioration of glass forming ability (GFA). The introduction of W significantly improved the thermal stability of the alloy system with glass transition temperature Tg and onset crystallization temperature Tx of Fe36Cr23Mo8W10C15B6Y2 BMG reached 923 K and 972 K, respectively. The W-bearing Fe-based BMGs also exhibited a very high hardness of 1400 HV and Young's modulus of 271 GPa, respectively. The extremely high thermal stability and elastic modulus were mainly derived from the strong chemical bonding between atoms. In addition, the large addition of W reduced the corrosion current density of the original alloy by an order of magnitude, which was mainly due to the formation of WO3 and the increase of MoO2 in the passivation film which inhibit the pit initiation and pit growth.
      原文链接:
    • NSTL
    • Elsevier

    Tailoring the magnetic properties and microstructure of Alnico 8 magnets by various Ti contents and processing conditions

    Rehman S.U.Liu H.Li S.Minglong Z....
    7页
    查看更多>>摘要：? 2022 Elsevier LtdShape anisotropy, developed as a result of spinodal decomposition (SD) is the basis for the hysteresis behavior of Alnico magnets. The SD process is sensitive to processing conditions and constituent elements. In this paper, the development of spinodal structure and its effects on magnetic properties and serviceability of Alnico 8 alloys are investigated. The Ti-content is varied between 2.5 and 7.5 wt%. The magnets are fabricated by conventional casting, homogenization, magnetic field annealing and tempering treatments. The magnetic properties of intrinsic coercivity, Hcj = 30 kA/m, remanence, Br = 0.53 T and maximum energy density, (BH)max = 6.03 kJ/m3 for 2.5 wt% Ti are increased to Hcj = 150 kA/m, Br = 0.0.88 T and (BH)max = 29.3 kJ/m3 for 6.5 wt% Ti alloy. These magnetic properties are 100% reversible up to 800 K. Furthermore, an alloy with 5.5 wt% Ti is directionally solidified and magnetic properties of Br = 1.01 T and (BH)max = 58.9 kJ/m3 are obtained. The evolution of mosaic nano structure, the mechanism of magnetic hardening and the interactions of various phases have been investigated.
      原文链接:
    • NSTL
    • Elsevier

    Tunable magnetocaloric effect at approximately room temperature by Y-substitution in Ho2Fe17

    Huang G.B.Du Y.S.Wu X.F.Ma L....
    8页
    查看更多>>摘要：? 2022 Elsevier LtdThe structure, magnetic transition and magnetocaloric effect of the intermetallic compounds (Ho2-xYx)Fe17 (x = 0, 0.5, 1 and 1.5) were investigated. The compounds crystallize into a Th2Ni17-type structure with the P63/mmc space group, as determined by Rietveld refinement of the XRD powder diffraction patterns. All the samples undergo a second-order magnetic transition from the ferromagnetic to paramagnetic state, and the Curie temperature decreases from 334 K (x = 0) to 314 K (x = 1.5) with increasing Y content. In the paramagnetic region, the reciprocal magnetic susceptibilities χ?1 for (Ho2-xYx)Fe17 (x = 0.5, 1 and 1.5) obey the Curie-Weiss law. The effective magnetic moment was determined to be 28.97 μB/f.u., 32.88 μB/f.u. and 33.78 μB/f.u., respectively, with corresponding paramagnetic Curie temperatures of 323 K, 308 K and 304 K. The maximum magnetic entropy changes for (Ho2-xYx)Fe17 (x = 0, 0.5, 1 and 1.5) are 3.0 J/kg K, 3.5 J/kg K, 3.8 J/kg K and 4.6 J/kg K, with corresponding refrigerant capacity values of 168 J/kg, 197 J/kg, 263 J/kg and 342 J/kg for a field change of 0–5 T. The tunable Curie temperature and considerable magnetocaloric effect indicate that (Ho2-xYx)Fe17 (x = 0, 0.5, 1 and 1.5) compounds are candidates for room-temperature magnetic refrigerants.
      原文链接:
    • NSTL
    • Elsevier

    Microstructure and phases investigations of W–Mo–Cu alloy prepared by large current electric field sintering

    Liu Y.Feng K.Chen S.Zhou H....
    8页
    查看更多>>摘要：? 2022 Elsevier LtdW–Mo–Cu alloy was fabricated by large current electric field sintering at a low temperature of 950 °C. The interrupted sintering at different sintering stages was performed to identify the phases and microstructure evolution during the densification process. The transmission electron microscope (TEM) images clearly show that the nanoscale phases form and distribute at the boundaries of W, Mo, and Cu phases. Moreover, the high-resolution TEM images incorporating with a selected area fast Fourier transform and inverse fast Fourier transform (IFFT) treatment present the structure of formed phases. Meanwhile, the lattice parameters calculated through X-ray diffraction patterns and IFFT images jointly evidence the existence of defects and atom diffusion during the sintering. The dislocations and lattice strain induced by the ultrahigh current and pressure provide the stored energy and nucleation sites, thus promoting the diffusion of elements and the formation of fine grains.
      原文链接:
    • NSTL
    • Elsevier

    Anomalous heat transfer near the martensite-austenite phase transition in Ni50Mn28Ga22-x(Cu, Zn)x (x = 0; 1.5) alloys

    Gamzatov A.G.Batdalov A.B.Aliev A.M.Khizriev S.K....
    6页
    查看更多>>摘要：? 2022 Elsevier LtdThe paper presents a detailed investigation of the thermal transport of the Ni50Mn28Ga22-x(Cu, Zn)x (x = 0; 1.5) alloys through specific heat, thermal diffusivity and thermal conductivity measurements. It is shown that the partial replacement of Ga atoms by Zn or Cu atoms leads to a convergence of magnetic and martensitic phase transition temperatures. Our measurements of the thermal diffusivity and thermal conductivity revealed that the behavior of these parameters in the phase transitions region is anomalous due to the coexistence of martensite-austenite phases and the effect of the latent heat of the phase transition. Moreover, the latent heat plays a crucial role in the appearance of a deep minimum of thermal diffusivity in the region of martensitic transformation for the Cu- and Zn-doped samples. Estimates of the phonon mean free path lph in martensitic and austenitic phase gave values of lph,mart = 1.5 nm and lph,aust = 1.9 nm, respectively. This implies that the main mechanism of phonon scattering is local structural inhomogeneities, which decrease sharply upon transition from martensite phase to the highly symmetric austenitic phase.
      原文链接:
    • NSTL
    • Elsevier

    Atomic structure of Cu60Ti20Zr20 metallic glass under high pressures

    Celtek M.
    11页
    查看更多>>摘要：? 2022 Elsevier LtdDuring the rapid cooling process, the atomic structure of the Cu60Ti20Zr20 ternary alloy under external pressure was investigated by molecular dynamics simulations using the embedded atom method potential. The effect of the pressure was discussed in detail by using a variety of analysis methods. Glass transition temperature determined by the modified Wendt-Abraham parameter was found to increase with increasing pressure. It was observed that the calculated total (or partial) pair distribution function and structure factor are in good agreement with the experimental x-ray data (with the ab-initio molecular dynamics results). The bond angle distributions of Cu-centered triplets were more consistent with ideal icosahedral clusters than that of Ti- and Zr-centered triplets. The dominant clusters for all pressures were icosahedral-like clusters that were not much affected by pressure. In addition to the bonds between Cu–Zr pairs shortening more easily under high pressure than other pairs, it is found that the Cu60Ti20Zr20 glassy alloy remained stable under pressure and its topological and atomic structures did not change much with pressure.
      原文链接:
    • NSTL
    • Elsevier

    Exploration of crystal growth behavior in Au-based metallic glass by nanocalorimetry

    Li S.Zhao B.Zhai Q.Gao Y....
    7页
    查看更多>>摘要：? 2022 Elsevier LtdThe Au49Ag5.5Pd2.3Cu26.9Si16.3 (at.%) bulk metallic glass is among the promising Au-based metallic glasses with the enhanced glass-forming ability and thermal stability. However, crystal growth kinetics during the crystallization of this metallic glass remains ambiguous. In this study, the rapid crystallization of a Au49Ag5.5Pd2.3Cu26.9Si16.3 bulk metallic glass in a wide temperature range was realized by nanocalorimetry. The underlying thermodynamic and kinetic features of crystal growth were ascertained based on the Cohen and Grest (C&G), Mauro-Yue-Ellison-Gupta-Allan (MYEGA) and Schmelzer models, and the adaptability of these three models was demonstrated. The maximum crystal growth rate (0.037 m/s) and corresponding temperature (595 K) estimated by these three models were similar but different crystal growth behaviors in the deeply undercooled melt were distinguished. With an increase in undercooling, the breakdown of the Stokes-Einstein relation was discovered, and a temperature-dependent decoupling exponent was demonstrated by the Schmelzer model, causing a divergence of crystal growth rate from that estimated by C&G and MYEGA models. Moreover, screw-dislocation-mediated growth was stated as the dominant crystal growth mechanism during the crystallization of the Au49Ag5.5Pd2.3Cu26.9Si16.3 bulk metallic glass.
      原文链接:
    • NSTL
    • Elsevier