制备了一种中等密度(约8.0 g/cm³)的难熔高熵合金Ti_0.5Zr_1.5NbTa_0.5Sn_0.2 (摩尔比),系统研究了热处理温度对合金组织结构和力学性能的影响。结果表明：铸态Ti_0.5Zr_1.5NbTa_0.5Sn_0.2合金组织为富Zr和富Ta bcc相以及晶内的板条状Zr₅Sn₃。随着热处理温度升高,富Ta bcc相体积分数逐渐减少,Zr₅Sn₃体积分数先增加后减少。当热处理温度为1400℃时,样品呈现近单相bcc结构。准静态条件下,系列样品均具有良好的压缩塑性变形能力；随着热处理温度的提高,合金屈服强度逐渐上升,1400℃热处理样品的屈服强度为1749 MPa。动态变形时,合金表现出明显的应变率强化效应,屈服强度显著增加,1400℃热处理样品的屈服强度达到2750 MPa,塑性变形量有所下降。强度随热处理温度提升的原因是9.8%的平均原子尺寸差带来了显著的固溶强化效果。

Refractory high-entropy alloys (RHEAs) have great application potential in extreme conditions due to their outstanding high-temperature properties. However, several issues, such as high density, poor room temperature plasticity, and high cost limit their practical application. A new Ti_0.5Zr_1.5NbTa_0.5Sn_0.2 (molar ratio) RHEA with a medium density of approximately 8.0 g/cm³ was prepared to address the aforementioned issues; the effects of heat treatment temperature on the alloy's microstructure and mechanical properties were systematically examined. The findings indicate that as-cast Ti_0.5Zr_1.5NbTa_0.5Sn_0.2 RHEA contains Zr-rich and Ta-rich bcc phases and lath-like Zr₅Sn₃ intermetallics in the crystal. The volume fraction of the Ta-rich bcc phase gradually decreases with the increase in heat treatment temperature, and Zr₅Sn₃ intermetallic first increases and then decreases. The sample presents a near single-phase bcc structure when the heat treatment temperature is 1400^oC. A series of samples have good compressive plastic deformation ability under quasi-static conditions, and the alloy's yield strength increased gradually with an increasing heat treatment temperature. The sample's yield strength quenched at 1400^oC is as high as 1749 MPa. The alloy showed strain rate strengthening effect under dynamic loading, and the yield strength significantly increased. The sample's yield strength quenched at 1400^oC reaches 2750 MPa; however, the plastic deformation ability is reduced. The reason why the strength increases with the heat treatment temperature is that the 9.8% average atomic size difference results in a significant solid solution strengthening effect.