Double Heterogeneous Structures Induced Excellent Strength-Ductility Synergy in Ni 40 Co 30 Cr 20 Al 5 Ti 5 Medium-Entropy Alloy

•Through an ingenious mechanical heat treatment process, a double heterogeneous structure alloy composed of heterogeneous grain structure and heterogeneous size phase was designed.•The double heterogeneous structure alloy simultaneously increases strength and ductility, demonstrating a remarkable strength–ductility synergy.•Double heterostructure alloys have superior mechanical properties compared to other high performance heterostructure alloys.