The effect of laser surface treatment for cellular structure-induced metastability in ferrous medium-entropy alloy

Laser treatment can create a non-equilibrium state through ultrafast heating and cooling rates, leading to changes in the local chemical composition. Given the sensitive dependence of transformation-induced plasticity (TRIP) on chemical composition, in this work, we combined the surface modification of laser treatment and metastability engineering. The resulting microstructure exhibits a cellular structure with solute segregation concentrated in the surface region, promoting TRIP behavior on the surface and improving the strain hardenability. The localized TRIP generates strain partitioning between the surface and center regions, resulting in dynamic heterostructure and a sustained synergistic effect. Therefore, the present alloy shows higher strength and enhanced strain hardening due to the local TRIP effect and dynamic heterostructure, compared to its counterpart. This work presents a new heterostructuring strategy by incorporating the cellular structure and metastability to control heterogeneous TRIP kinetics.