Influence of solute elements and grain gradient on the mechanical properties of Fe-Mn alloys

This study systematically investigates the effects of solute atoms and gradient nanograined (GNG) on the mechanical properties and microscopic deformation mechanisms of FeMnSiC alloys. Using molecular dynamics simulations, the influence of Mn, Si, and C additions on the stress–strain response, dislocation evolution, phase transformation, and grain boundary migration in homogeneous Fe-based alloys was analyzed. The results indicate that Mn and C enhance strength through solid solution strengthening, while Si improves work hardening capability but reduces both strength and elasticity. Furthermore, the GNG design significantly increases Young’s modulus and average flow stress while maintaining high tensile strength, exhibiting an excellent synergy of strength, elasticity, and resistance to plastic deformation. Microscopic mechanism analysis reveals that the GNG facilitates orderly stress transfer from coarse-grained to fine-grained regions, promotes the accumulation of GNDs, and enhances back stress strengthening, thereby effectively suppressing local strain concentration and improving work hardening capacity. Additionally, the spatial inhomogeneity of phase transformation and dislocation evolution in the GNG further elucidates the structural origin of its performance optimization. This study provides a theoretical basis and new material design insights for developing high-performance Fe-based alloys.