Improving strength-ductility synergy in 301 stainless steel by combining gradient structure and TRIP effect

Here we investigate the microstructure and mechanical properties of gradient-structured 301 stainless steel synthesized by surface mechanical attrition treatment. Microstructure gradient in both martensite content and grain size, from nanostructured (NS) surface with high volume fraction of martensite to coarse-grained (CG) austenite interior, is identified in the mechanical gradient surface layer. Gradient samples exhibit excellent strength-ductility synergy due to the structure gradient-induced synergistic hardening and phase transformation induced plasticity (TRIP), i.e., combination of gradient and TRIP effects. Comparative analysis reveals that mechanical gradient can promote the phase transformation process, i.e. encouraging the TRIP effect.