Intermetallics最新文献

With the rapid development of third-generation semiconductors, there is an urgent need to develop high-performance soft magnetic Fe-based metallic glasses tailored particularly for their high-frequency applications. In this work, new Fe_76−yB₇C₇P₇Si₃Mo_y−xCr_x (y = 0, 1, 2, 3 at.%, x ≤ y) alloys with relatively high glass-forming ability (GFA) were developed. The effects of replacing Mo with Cr on GFA, thermodynamic properties, soft magnetic properties, electrical resistivity (ρ), and corrosion resistance at different Fe contents were systematically studied. The possible causes of GFA variation were discussed. The results show that the addition of a small amount of Cr replacing Mo under different Fe contents would not lead to a decrease in GFA. The critical sizes of Cr-containing glassy alloys are 1–2.5 mm. These alloys possess relatively high saturation magnetization (M_s) of 1.29–1.41 T and lower coercivity (H_c) of 0.7–1.8 A/m, contributing to the reduction of hysteresis loss. In addition, Cr increases ρ of the alloys, reaching up to 162 μΩ cm, which is beneficial to reducing eddy current loss at high frequency. Furthermore, Cr effectively enhances corrosion resistance, thereby increasing the service life of the alloys in harsh environments. The role of Cr in these aspects makes it a beneficial element in soft magnetic metallic glasses for high-frequency applications.

To enhance the hydrogen storage property, elements Mn in Ti₃₃V₃₇Mn₃₀ alloy were partially substituted with varying concentrations of elements Cr. The Ti₃₃V₃₇Mn₂₄Cr₆ variant, which exhibited superior performance, was selected for further analysis. Ti₃₃V₃₇Mn₂₄Cr₆ samples were first heat-treated separately at 773K, 973K and 1173K for 2h, and then water-quenched. The effect of Cr substitution and heat treatment on the microstructure and de-/hydriding properties of Ti₃₃V₃₇Mn_30-xCr_x alloys were investigated. As-cast alloys were composed of BCC phases mainly, along with some C14 Laves phases and Ti-rich phases. The lattice parameter of BCC phases in Ti₃₃V₃₇Mn₂₄Cr₆ increased to 3.053 Å. Cr substitution changed the tetrahedral gap of the alloy. At 298K, the initial hydrogen absorption capacity and the maximum hydrogen desorption capacity of Ti₃₃V₃₇Mn₂₄Cr₆ were raised to 3.07 wt% and 1.81 wt%, respectively. The lattice parameter of Ti₃₃V₃₇Mn₂₄Cr₆ alloys heat-treated at 773K also enlarged to 3.056 Å. Elevating the heat treatment temperature to 973K and 1173K significantly raised the proportion of C14 Laves phases in the alloy. Hydrogen storage performance of heat-treated alloys was examined at 298K. The results suggested that the heat-treated alloys could be fully activated after one hydrogen ab-/desorption cycle. Ti₃₃V₃₇Mn₂₄Cr₆ alloy heat-treated at 773K achieved the maximum hydrogen desorption capacity of 1.83 wt%, with an accelerated hydrogen ab-/desorption rate.

The influence of the potential for film formation and immersion time on the corrosion resistance of the passive film formed on Fe-based amorphous coating was thoroughly investigated. The semiconducting properties and chemical composition of the passive films were analyzed employing Mott-Schottky and XPS techniques. Results indicate that the stability of the film diminished as the potentials and immersion periods increased. The structural properties and chemical composition of film played a crucial role in the corrosion resistance of the coating in a chloride electrolyte. The accumulation of cation vacancies and the formation of metal chlorides increased the likelihood of film rupture, ultimately leading to pitting.

In this study, two Mo₂FeB₂-type multiple rare-earth-containing MRE₂Cu₂In (MRE = Dy_1/3Ho_1/3Er_1/3 and Ho_1/3Er_1/3Tm_1/3; space group P4/mbm, No. 127) compounds are prepared via arc-melting method and systematically determined regarding their structural and magnetic properties, magnetic phase transition (MPT), and magnetocaloric (MC) performances. They undergo typical second-order MPT at low temperatures. The MC effect and MC performances of the present MRE₂Cu₂In compounds at low temperatures are assessed using magnetic entropy changes, refrigerant capacity, and temperature-averaged entropy changes. The values of these parameters are comparable to most updated candidate materials for low-temperature magnetic cooling, making the present MRE₂Cu₂In compounds considerable for practical applications.

To clarify the initial microstructure dependent γ′-coarsening behavior, a corrosion-resistant Ni-based superalloy with the varied γ′-size were prepared by changing the primary aging heat treatment temperature. The microstructural evolution was investigated during long term thermal exposure (up to 3000 h) at 900 °C and 1000 °C, respectively. It was found that Cr, Co, and Mo preferentially partition to γ-matrix, while Ta, Ti, Al, Ni, and W partition to the γ′-phase. The abnormal partition of W to the γ′-phase can be attributed to the low content of Ta in CM247 LC alloy. Furthermore, the γ′-coarsening behavior can be divided into two stages. During the early stage of coarsening (<1000 h), the coarsening rate obeys the classical LSW model with the cube rate law. As the increase of the initial γ′-size, the γ′-coarsening rate obviously increases, which can be mainly attributed to the increased solute diffusion capability in the γ-matrix and the higher γ'/γ interfacial energy. By contrast, there is an apparent γ′-coalescence during the later stage of coarsening (1000 h–3000 h). The temperature plays a more dominant role on the γ′-coarsening rate than the duration times during thermal exposure.

Nb silicide coatings modified with active elements have good oxidation resistance, but there is a lack of systematic research on their oxidation behavior at high temperatures above 1250 °C. The aim of this work is to investigate the oxidation behavior of an Al–Y modified silicide coating on Nb–Si based alloy in the temperature range from 1250 °C to 1560 °C. After oxidation at 1250 °C, the scale displays a typical layered structure consisting mainly of a TiO₂ outer layer, an amorphous SiO₂ matrix layer embedded with TiO₂ and ZrSiO₄, and an inner layer consisting of SiO₂ and Cr₂O₃. Above 1350 °C, the evaporation reaction of Cr₂O₃ into CrO₃ (g) is significantly accelerated and Cr₂O₃ disappeared gradually with temperature or time. The TiO₂ layers covering on the scales formed at 1250–1500 °C grow along the crystallographic orientation of [100]. The micropores formed on the surface of TiO₂ should be attributed to the further oxidation of Cr₂O₃ into volatile oxide CrO₃ (g). The scales exhibit a similar structure consisting mainly of a SiO₂ glass matrix embedded with ZrSiO₄ and a surface TiO₂ layer until 1500 °C. Above the eutectic temperature of SiO₂–TiO₂ system, the scale is mainly composed of a matrix layer of SiO₂–TiO₂ eutectic embedded with block TiO₂ particles, and a thin SiO₂ interface layer at 1560 °C. The degeneration path of the (Nb,X)Si₂ coating is (Nb,X)Si₂ → (Ti,Nb)₅Si₄ → γ-(Nb,X)₅Si₃.

In this investigation, we explore the impact of the Nb–Al ratio on the microstructural and mechanical properties of high-entropy superalloys (HESAs), focusing on hierarchical microstructures. Utilizing a series of HESAs with varying Nb–Al ratios, our study employs advanced characterization techniques, including differential scanning calorimetry (DSC) for thermal analysis, electron probe micro-analyzer (EPMA) for compositional analysis for the design of a homogenization treatment at 1500 K/24 h. Transmission electron microscopy (TEM) reveals that the increasing Nb–Al ratio refines the γ' precipitates and influences the size and volume fraction of embedded hierarchical γ particles. ThermoCalc equilibrium phase analysis and Vegard's-law calculations reveal a minimal lattice misfit between these phases, highlighting the interplay between Nb–Al ratio and phase stability. The increasing Nb–Al ratio inhibits the formation of hierarchical γ particles. We observe an enhancement in hardness from 433 HV to 492 HV with an increasing Nb–Al ratio. This study provides valuable insights into the role of Nb and the Nb–Al ratio in HESAs with hierarchical microstructures, demonstrating its significant influence on γ particle formation within γ' precipitates and mechanical strength. The findings advance our understanding of alloy design and pave the way for developing advanced HESAs for high-temperature applications.

A novel Fe₈₇Pr₁₁B₂ metallic glass that exhibits outstanding magnetocaloric effect near room temperature was prepared into the shape of amorphous ribbons. The ribbon exhibits soft magnetic properties and high saturation magnetization at 200 K, which is much lower than its Curie temperature at 325 K. No obvious spin-glass-like behavior was found above 200 K. The almost highest maximum magnetic entropy change (−ΔS_m^peak) among Fe-based metallic glasses near the hot end of a residential magnetic refrigerator is most likely attributed to the high concentration of Pr and low content of B in the Fe₈₇Pr₁₁B₂ amorphous ribbon. The high −ΔS_m^peak, large refrigeration capacity (RC) and adiabatic temperature rise (ΔT_ad) make the Fe₈₇Pr₁₁B₂ amorphous alloy better candidate for the potential component of a refrigerant working in a high-efficiency residential magnetic refrigerator.

Presently, interfacial intermetallic compounds play a vital role in determining the reliability of solder joints due to their intrinsic mechanical property. Especially for Zn–Al solder joints, the interfacial Cu–Zn IMCs grow significantly without diffusion barriers. This work comprehensively investigated the mechanical properties of interfacial IMCs in Zn–Al solder joints with and without the Ni–W–P diffusion barrier by nanoindentation tests and first-principles calculations. The nanoindentation results show that the elastic moduli of CuZn₄, Cu₅Zn₈, CuZn and Al₃Ni₂ were 68.45 ± 1.4 GPa, 142.6 ± 2.3 GPa, 94.7 ± 1.16 GPa, and 221 ± 18.9 GPa, respectively. Their corresponding hardness were 1.03 ± 0.04 GPa, 5.98 ± 0.23 GPa, 1.38 ± 0.16 GPa, and 17.7 ± 0.16 GPa. Through first-principles calculations, the bulk modulus of CuZn and Cu₅Zn₈ exhibits isotropic behaviour, while CuZn₄ and Al₃Ni₂ demonstrate anisotropy. In addition, the bulk modulus, shear modulus, Young's modulus and hardness values of Al₃Ni₂ are considerably higher when compared to those of Cu–Zn intermetallic compounds.

Oxidation behavior of a Ni–Co-based superalloy prepared by vacuum induction melting (VIM) plus electron beam smelting layered solidification technology (EBSL) and VIM plus electro slag remelting (ESR) at 1180 °C was investigated. The predominant oxides from the outer layer to the inner layer are TiO₂, Cr₂O₃, (Al, Ti)-rich oxide and Al₂O₃, respectively. The (Al, Ti)-rich oxide is considered to be Al₂Ti₄O₉, which is formed by TiO₂ and Al₂O₃. At high temperature, the external oxides experienced significant spalling, particularly in ESR-alloy, which indicated that the EBSL-alloy is more preferable in terms of oxidation resistance. This can be attributed to the presence of finer grains in EBSL-alloy, which facilitates the diffusion of elements and promotes the rapid formation of oxidation scales on the surface of the alloy. Additionally, the presence of a TiO₂ layer cover on Cr₂O₃ reduces the degree of spalling of oxides in EBSL-alloy.