Balanced mechanical properties of Al0.3CoCrFeNiTix high-entropy alloys by tailoring Ti content and heat treatment

Al0.3CoCrFeNiTix (x = 0.025, 0.075, 0.15) high-entropy alloys (HEAs) were designed to investigate the impacts of Ti addition and the aging temperature (700–900 °C) on the mechanical properties of the alloys. The alloy aged at 700 °C with x = 0.15 yielded the highest ultimate tensile strength (UTS) and large fracture elongation at both room temperature and 700 °C. The UTS is 1299 MPa with fracture elongation up to 31.6% at room temperature, and 769 MPa with 32.5% at 700 °C. The product of strength and elongation of Al0·3CoCrFeNiTi0.15 is higher than the reported value of other similar FCC HEAs at elevated temperature. The reason for the outstanding balanced mechanical properties of the alloy is the uniformly distributed L12 and B2 particles. Ti promotes the precipitation of L12 phase and the precipitation temperature increased from 770 to 890 °C as Ti content increased. The amount of B2 phase reached a maximum at 900 °C with x = 0.15. The B2 particles at grain boundaries render the different variation tendency of ductility at 700 °C from that at room temperature.