Synthesis of ultrafine dual-phase structure in CrFeCoNiAl_(0.6)high entropy alloy via solid-state phase transformation during sub-rapid solidification

High entropy alloys(HEAs)with superb mechanical properties have been traditionally produced by solid-ification and subsequent heat treatment,In this paper,we demonstrate a new route via one-step process using sub-rapid cooling.Under proper cooling rates,the CrFeCoNiAl^(0.6) HEA could form ultrafineFCC+BCC dual-phase structure.By varying cooling rate,we can control the fraction of the BCC phaseand refinement of FCC microstructures that have tunable mechanical properties in yield strength and hardness ranging from~580 to~1460 MPa and~260 to~550 Hv.We show that the structure-property-processing relation originates from the sideplate microstructures formed during fast cooling that havespecific crystallographic orientation relationship between the FCC and BCC phases and chemical segrega tion.This work provides a new setting for better understanding of the solid-state phase transformation in HEAs under sub-rapid solidification conditions as well as a novel method for development of high-performance HEAs.