Refractory high-entropy alloys (RHEAs) composed of Ti, Zr, Hf, and Nb have emerged as promising materials for high-temperature aerospace applications due to their exceptional balance of strength and toughness, coupled with a reduced density and softening resistance. This study delves into the influence of alloy composition on the mechanical properties, a pivotal aspect in the design of RHEAs. We investigate a series of TiZrHfNb ( = 14, 18, 22, 26, 30, 34) alloys, prepared through suction casting and homogenization treatments. The phases, microstructure, and fracture morphology of these alloys are analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD), subsequent tensile tests provide insights into the strength and elongation characteristics of alloys. The homogenized alloys consistently exhibit one BCC phase with equiaxed grains, whereas the fracture mode shifts from intergranular to transgranular, and return to intergranular as the Zr content increases. Experimental results reveal an asymmetry mechanical behavior, alloys with higher Ti content display superior toughness (elongation 17.83 % for Ti = 34 at%) compared to those with higher Zr content (elongation 16.05 % for Zr = 34 at%). Among them, the TiZrHfNb alloy achieves the peak tensile strength of 695.25 MPa, indicating an inverse relationship between strength and toughness. Solid-solution strengthening and chemical short-range orderings emerge as the predominant contributors to the overall strength of the TiZrHfNb alloys. To gain a deeper understanding of the mechanical behavior at the atomic scale, we performed first-principles calculations to investigate the elastic properties and charge density of TiZrHfNb alloys in the BCC structure. These calculations shed light on the underlying mechanisms governing the strength and toughness behavior. The present work offers valuable insights into the design of mechanical properties of TiZrHfNb RHEAs, serving as a paradigm for future materials development in this field.

中文翻译：

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通过锆含量变化揭示 Ti48-xZrxHf26Nb26 高熵合金的力学行为

由 Ti、Zr、Hf 和 Nb 组成的难熔高熵合金 (RHEA) 因其强度和韧性的出色平衡，以及较低的密度和抗软化性而成为高温航空航天应用的有前途的材料。这项研究深入探讨了合金成分对机械性能的影响，这是 RHEA 设计的一个关键方面。我们研究了一系列通过吸铸和均质化处理制备的 TiZrHfNb (= 14、18、22、26、30、34) 合金。使用 X 射线衍射 (XRD)、扫描电子显微镜 (SEM) 和电子背散射衍射 (EBSD) 分析这些合金的物相、微观结构和断口形貌，随后的拉伸测试可深入了解合金的强度和伸长率特性。均质合金始终呈现出具有等轴晶粒的 BCC 相，而断裂模式从沿晶转变为穿晶，并随着 Zr 含量的增加又返回到晶间。实验结果揭示了不对称的机械行为，与 Zr 含量较高的合金（Zr = 34 at% 时伸长率为 16.05%）相比，Ti 含量较高的合金表现出优异的韧性（Ti = 34 at% 时伸长率为 17.83%）。其中，TiZrHfNb合金的峰值抗拉强度达到695.25 MPa，表明强度和韧性之间呈反比关系。固溶强化和化学短程有序化成为 TiZrHfNb 合金整体强度的主要贡献者。为了更深入地了解原子尺度的机械行为，我们进行了第一性原理计算来研究 BCC 结构中 TiZrHfNb 合金的弹性性能和电荷密度。这些计算揭示了控制强度和韧性行为的基本机制。目前的工作为 TiZrHfNb RHEA 的机械性能设计提供了宝贵的见解，可作为该领域未来材料开发的范例。