Abstract: A novel low-activation Ti_1.5ZrV_0.5Ta_0.5 refractory high-entropy alloy (RHEA) was designed as a potential candidate for nuclear reactor application. At room temperature, it had an elongation of 8.4% and a yield strength of 1096 MPa. The phase evolution of this alloy and its effect on properties was investigated. At 400 °C, the solid solution bcc₁ transformed into the fcc phase and bcc₂ phase, and the ω phase and α phase also appeared. At 600 °C, the ω phase and α phase disappeared, and the microstructure of the alloy was composed of the fcc phase and bcc₂ phase. When the temperature was up to 1200 °C, the fcc phase and bcc₂ phase re-transformed into solid solution bcc₁ phase. The precipitation of ω phase and α phase caused a sharp increase in strength and a decrease in plasticity. Meanwhile, the appearance of the fcc phase led to a simultaneous decrease in strength and ductility, due to larger stress concentrations at the fcc/bcc interface. Besides, the formation mechanism of each phase in the alloy was discussed in detail.

Key words: Low-activation, Refractory high-entropy alloy, Phase evolution, Phase formation mechanism, Strengthening mechanism