Strong room temperature work hardening in a dual heterogeneous structured ferrous medium entropy alloy

In this work, a novel (Fe₆₅Ni₁₅Cr₁₀Co₁₀)₉₂Ti₅Al₃ medium-entropy alloy (MEA) with a dual heterogeneous structure was produced by adding Ti and Al in our previous reported Fe₆₅Ni₁₅Co₁₀Cr₁₀ MEA. The dual heterogeneous structure consists of the partial recrystallization matrix and heterogeneous nanoprecipitates. The tensile tests show that the MEA displays an ultra-high ultimate tensile strength (1519 MPa) and work hardening extent (559 MPa) at room temperature. The addition of Ti and Al produces precipitates while lowering FCC stability. This contributes to a continuous FCC→BCC martensitic transformation and a consequent transformation-induced plasticity (TRIP) effect during whole plastic deformation. Therefore, the excellent mechanical properties are attributed to the synergism of multiple mechanisms, including the hetero-deformation induced (HDI) strengthening, precipitation strengthening, and TRIP effects. The alloy design strategy in this paper has guiding significance for the development of high-performance ferrous MEAs.