Creep resistance, which is one of the most important deformation modes, is rarely reported for refractory high entropy alloys (RHEAs). The experiment investigated the high-temperature creep mechanism of Ti-Ta-Nb-Mo-Zr RHEA prepared by laser powder bed fusion (LPBF) technology. The high cooling rate of LPBF suppresses most of the elemental segregation, but there are still over-solidified precipitates and a few continuous precipitates (CP). In the range of 923–1023 K, the stress exponent and activation energy were determined to be 3.2–3.4 and 261.5 ± 19.5 kJ/mol, respectively. Compared with other conventional alloys and HEAs, a large reduction of the minimum creep rate is found in the LPBF-built TiTaNbZrMo RHEA, indicating a significant improvement in high-temperature properties. The dislocation tangles at the interface is formed during the creep process and new Zr-rich CP phases are generated in the dislocation tangles region. The interfacial dislocation tangles is the result of the interaction between dislocations and two-phase mismatch stresses. The dislocation tangles prevents dislocations from further cutting the matrix phase, which is very favorable to the high-temperature creep performance. At the same time, the formation of this dislocation tangles greatly accelerates the nucleation process and growth rate of the new CP phase. The present work provides a pathway to design novel HEAs with improved high-temperature creep resistance.

中文翻译：

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激光粉末床熔合Ti-Ta-Nb-Mo-Zr难熔高熵合金的高温蠕变机理


抗蠕变性是耐火高熵合金（RHEA）最重要的变形模式之一，但很少有报道。实验研究了激光粉末床熔合（LPBF）技术制备的Ti-Ta-Nb-Mo-Zr RHEA的高温蠕变机理。 LPBF的高冷却速率抑制了大部分元素偏析，但仍然存在过凝固析出物和少量连续析出物（CP）。在 923–1023 K 范围内，应力指数和活化能分别确定为 3.2–3.4 和 261.5 ± 19.5 kJ/mol。与其他传统合金和 HEA 相比，LPBF 构建的 TiTaNbZrMo RHEA 的最小蠕变速率大幅降低，表明高温性能显着改善。蠕变过程中在界面处形成位错缠结，并且在位错缠结区域中生成新的富Zr CP相。界面位错缠结是位错和两相失配应力之间相互作用的结果。位错缠结阻止位错进一步切割基体相，这对于高温蠕变性能非常有利。同时，这种位错缠结的形成大大加速了新CP相的成核过程和生长速度。目前的工作为设计具有改进的高温抗蠕变性的新型 HEA 提供了一条途径。