Hall-petch relationship and heterogeneous strength of CrCoNi medium-entropy alloy

In this work, we mainly focused on single phase face-centered cubic (FCC) type CrCoNi medium-entropy alloy (MEA), fabricated the homogeneous and heterogeneous grain structure through heavily deformation and subsequent annealing treatment, then investigated the Hall-petch relationship and heterogeneous strength of CrCoNi MEA. The experimental results show that, the large friction stress of fully-recrystallized CrCoNi MEA resulted from the severe lattice distortion, short-time partial-recrystallized annealing and abundant thermal twinning facilitated the heterogeneous structure with multiple gain size. The heterogeneous structure (i.e. partial-recrystallized structure) exhibited a superb strength-ductility synergy in comparison with nano-grained structure and/or ultrafine-grained structure in CrCoNi MEA. The results would provide the comprehensive understanding of CrCoNi MEA, as well as the essentials for further development and applications of FCC type multicomponent alloys.