Precipitation-hardened refractoryTi-Nb-Hf-Al-Ta high-entropy alloys

Abstract

This study reports the structure and mechanical properties of new refractory Ti37.5Nb12.5Hf25Al25, Ti40Nb30Hf15Al15, and Ti40Nb20Ta10Hf15Al15 (at.%) high entropy alloys. After annealing at 1200 °C for 24 h, the program alloys had a single-phase B2 structure. Further annealing at 600 °C for 24 h resulted in the formation of Widmanstatten orthorhombic particles (O-phase) in the bcc matrix. The Ti40Nb30Hf15Al15 and Ti40Nb20Ta10Hf15Al15 alloys annealed at T = 1200 °C showed moderate strength and good ductility (>50%) at 22 and 600 °C; while the Ti37.5Nb12.5Hf25Al25 alloy was stronger, but less ductile at both temperatures. Subsequent annealing at T = 600 °C significantly increased the strength of the Ti40Nb30Hf15Al15 alloy at 22 and 600 °C, maintaining compressive sufficient ductility at room-temperature.