Microstructure and mechanical properties of Al_x(TiZrTa_0.7NbMo) refractory high-entropy alloys

An Al_x(TiZrTa_0.7NbMo) (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) series of refractory high-entropy alloys were prepared by a vacuum-arc melting process and annealed. The effects of aluminum (Al) addition on the microstructure, room temperature, and high temperature mechanical properties of refractory high-entropy alloys were systematically examined and the strengthening mechanism analyzed and discussed. The results showed that, the phase composition of the alloy was BCC₁ and BCC₂ phases in the absence of Al. Precipitated phase AlZr₃ formed in the alloy when Al was added. This series of refractory high entropy alloy has good strength at room temperature and high temperature. The compressive yield strength of Al_0.5(TiZrTa_0.7NbMo) alloy at room temperature was 1984 MPa and the compressive yield strength at 800 °C was 714 MPa. All alloys have plastic strain variables of 10.2–34.8 %, showing excellent room temperature plasticity. The increase in yield strength at room temperature primarily resulted from solution and precipitation strengthening. At high temperatures, precipitation strengthening became the dominant strengthening method. These research findings are expected to facilitate the understanding of the influence trends and mechanism of action of Al in refractory high-entropy alloys and serve as a reference for the design and development of Al-containing refractory high-entropy alloys.