Abstract This study reports the microstructure, phase composition, mechanical properties and oxidation behavior of NbTaTi and NbTaZr ternary equiatomic alloys. These ternary components, together with earlier reported NbTiZr and MoNbTi, are commonly observed in refractory high entropy alloys (RHEAs) with a single-phase BCC or multi-phase crystal structures. Therefore, the reported information about these ternary alloys is thought to be useful for the development of advanced RHEAs. While NbTiZr and MoNbTi are single-phase BCC structures, NbTaTi and NbTaZr are multi-phase alloys. NbTaTi consists of a BCC matrix and discontinuous, Ti-rich precipitates with BCC and FCC crystal structures. NbTaZr consists of a co-continuous spinodal mixture of two BCC phases, one of which is rich in Ta and Nb and another is rich in Zr, and it also contains a Zr-rich HCP phase in the form of coarse grain-boundary particles. NbTaTi has compression yield stress of 724 MPa at 25 °C, 268 MPa at 800 °C and 129 MPa at 1200 °C. NbTaZr is stronger, with the compression yield stress of 1027 MPa at 25 °C, 530 MPa at 800 °C and 183 MPa at 1200 °C. Both alloys show rapid oxidation with formation of complex oxides during holding at 1200 °C.

中文翻译：

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NbTaTi和NbTaZr难熔合金的显微组织、力学性能和氧化行为

摘要 本研究报告了NbTaTi 和NbTaZr 三元等原子合金的显微组织、相组成、力学性能和氧化行为。这些三元组分，连同早先报道的 NbTiZr 和 MoNbTi，通常在具有单相 BCC 或多相晶体结构的难熔高熵合金 (RHEA) 中观察到。因此，有关这些三元合金的报告信息被认为对开发先进的 RHEA 很有用。NbTiZr 和 MoNbTi 是单相 BCC 结构，而 NbTaTi 和 NbTaZr 是多相合金。NbTaTi 由 BCC 基体和不连续的、具有 BCC 和 FCC 晶体结构的富钛沉淀物组成。NbTaZr 由两个 BCC 相的共连续旋节线混合物组成，其中一个富含 Ta 和 Nb，另一个富含 Zr，它还包含粗晶界颗粒形式的富含 Zr 的 HCP 相。NbTaTi 的压缩屈服应力在 25 °C 时为 724 MPa，在 800 °C 时为 268 MPa，在 1200 °C 时为 129 MPa。NbTaZr 更强，压缩屈服应力在 25°C 时为 1027 MPa，在 800°C 时为 530 MPa，在 1200°C 时为 183 MPa。两种合金在保持在 1200 °C 时都表现出快速氧化并形成复杂的氧化物。