The refractory high-entropy alloy (RHEA) with a body-centered-cubic (BCC) solid-solution structure has excellent high-temperature softening resistance, which has attracted wide interest in the field of high-temperature alloys. However, its limited room-temperature plasticity has greatly hindered its engineering application. To obtain an excellent strength-plasticity matching relationship, in this reported study, the Ta content in the high-entropy alloy (HEA) was adjusted to rectify this shortcoming. A series of TiZrTaNbMo (x = 1.0, 0.9, 0.8, 0.7, and 0.6 at. percent, at%) RHEAs were prepared using the vacuum arc-melting technique, and the microstructure and mechanical properties of these RHEA alloys were systematically investigated. The experimental results show that the TiZrTaNbMo RHEAs are composed of main BCC1 and minor BCC2 phases, which exhibit a dendritic structure. By reducing the Ta content, the elemental segregation caused by the non-equilibrium solidification is reduced. In terms of mechanical properties, with the decrease of Ta content, the hardness and room-temperature yield strength of the alloy decreases slightly, but the room-temperature plasticity increases significantly. The Ta0.7 alloy has the highest plasticity (34.8 %), which is about twice that of the equimolar Ta 1.0 alloy, while the yield strength remained at 1297 MPa. The excellent mechanical properties of the alloys can be attributed to solid-solution strengthening and the formation of moderate amounts of interdendritic regions. The interaction between slip bands and dislocations formed during compression of the Ta0.7 alloy decreased its work hardening. Moreover, the theoretical model of solid-solution strengthening elucidates that the calculated values of the alloy’s yield strength are consistent with that obtained experimentally.

中文翻译：

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新型TiZrTaxNbMo难熔高熵合金的显微组织演化和力学行为

具有体心立方（BCC）固溶体结构的难熔高熵合金（RHEA）具有优异的抗高温软化能力，引起了高温合金领域的广泛兴趣。但其室温塑性有限，极大地阻碍了其工程应用。为了获得优异的强度-塑性匹配关系，在本研究中，通过调整高熵合金（HEA）中的Ta含量来纠正这一缺点。采用真空电弧熔炼技术制备了一系列 TiZrTaNbMo (x = 1.0、0.9、0.8、0.7 和 0.6 at.%, at%) RHEA，并对这些 RHEA 合金的显微组织和力学性能进行了系统研究。实验结果表明TiZrTaNbMo RHEAs由主要的BCC1相和次要的BCC2相组成，呈现出树枝状结构。通过降低Ta含量，减少了非平衡凝固引起的元素偏析。力学性能方面，随着Ta含量的降低，合金的硬度和室温屈服强度略有下降，但室温塑性显着增加。 Ta0.7合金的塑性最高（34.8%），约为等摩尔Ta 1.0合金的两倍，而屈服强度仍保持在1297 MPa。合金优异的机械性能可归因于固溶强化和适量枝晶间区域的形成。 Ta0.7 合金压缩过程中形成的滑移带和位错之间的相互作用降低了其加工硬化。此外，固溶强化的理论模型表明，合金屈服强度的计算值与实验结果一致。