Nanoscale B2 precipitation and strengthening behavior in Al_0.5CoCrFeNi high-entropy alloy

The precipitation hardening high-entropy alloys (HEAs) have attracted extensive research interest for their enhanced strength yet considerable ductility. In this study, the Al_0.5CoCrFeNi HEA strengthened by nanoscale B2 phases was obtained after aging at temperature of 800 °C – 900 °C. The evolution of the B2 precipitation and the mechanical properties of Al_0.5CoCrFeNi alloy were investigated after different thermomechanical treatments. The volume fraction and the length–width ratio of the B2 phases in the alloy increase with the increase of the aging time. After aging at 850 °C for 16 h, the yield strength of the alloy reaches 514 MPa via Orowan strengthening mechanism of the B2 phases. Additionally, the introduction of pre-deformation before aging promotes the formation of B2 phases, which results in strength enhancement of the alloy via precipitation strengthening and work hardening.