Compositional effect on microstructure and mechanical properties of AlNbTiZr-based refractory high entropy alloys

This study aims to investigate the phase composition, microstructure, and mechanical properties of three refractory high-entropy alloys (RHEAs): Al 7 (NbTiZr) 93 , Al 7 (NbTiZrMo) 93 , and Al 7 (NbTiZrTa) 93 . The as-cast Al 7 (NbTiZr) 93 alloy exhibits a single-phase BCC structure, with a yield strength (YS) of 1050 MPa at room temperature. The addition of Mo and Ta leads to the formation of Al 7 (NbTiZrMo) 93 and Al 7 (NbTiZrTa) 93 alloys with BCC-B 2 and B 2-FCC dual-phase structures, whose YS values reach 1741 MPa and 2350 MPa, respectively. At 800 degrees C, trace amounts of ordered B 2 phase are generated in the Al 7 (NbTiZr) 93 matrix, and the YS decreases from 1050 MPa at room temperature to 219 MPa at 800 degrees C. In the Al 7 (NbTiZrMo) 93 alloy, the 10 nm B 2 precipitates grow to several hundred nanometers, and the YS decreases to 431 MPa after compression at 800 degrees C. In the Al 7 (NbTiZrTa) 93 alloy, the grid B 2-FCC structure at room temperature transforms into a disordered BCC structure at 800 degrees C, yet possessing the YS of 908 MPa and demonstrating acceptable ductility. Moreover, Ta exhibits the better structural and performance matching than Mo in AlNbTiZr-based RHEAs. Therefore, it opens up new prospects for regulating the structure and high-temperature performance of AlNbTiZr-based RHEAs.