Development of high-strength Co-free high-entropy alloys hardened by nanosized precipitates

A series of novel Co-free high-entropy alloys (HEAs) were developed by engineering nanoprecipitation in Fe-Ni-Cr-Mn-Al-Ti system, which exhibit a good combination of low cost, high strength and good ductility. The effects of Ti/Al ratio (from 0.6 to 1.7) on phase structures and mechanical properties were carefully investigated. Specifically, the alloy with a high Ti/Al ratio of 1.7 gives a high tensile strength of 1.25 GPa with a good ductility over 20 %, obviously outperforming other Co-free HEAs. The strain-hardening behaviors and deformation micro-mechanisms were analyzed by transmission electron microscope, which reveals the structural origins of their superior mechanical properties.