Two-step rolling and annealing makes nanoscale 316L austenite stainless steel with high ductility

Conventional steels can be strengthened by grain refinement to the nano-/ultrafine-grained regime, but usually at the expense of their ductility. In present study, nanoscale 316 L austenite stainless steel, prepared via an aluminothermic reaction, with high ductility can be obtained by two-step rolling and annealing. Firstly, the as cast steel consists of micro/nano crystalline austenite matrix. Then the steels undergone two-step rolling and annealing to tune tensile properties through microstructure tailoring. The two-step rolling can effectively enhance the yielding strength from 207 to 1007 MPa, but result in the degradation of ductility. Satisfactorily, the rolled steel followed annealed (R&A) exhibited an excellent ductility and without dramatically loss of strength, which originates from micro/nano crystalline and duplex phases microstructure. The nonuniform strain of micro- and nano-crystalline boundaries and phase interface leads to strain gradient, developing strain partitioning and back stress work hardening responsible for large ductility. This optimized process could be candidate for other engineering materials prepared by aluminothermic reaction to achieve combination of strength and ductility.