Microstructural evolution and strain hardening behavior of a novel two-stage warm rolled ultra-high strength medium Mn steel with heterogeneous structures

Abstract

A heterostructured medium Mn steel with duplex phases (ferrite and austenite) and multiple morphologies (lath-typed and granular) is fabricated by a novel two-stage warm rolling process and subsequent intercritical annealing. The obtained sample exhibits excellent mechanical properties with the yield strength and ultimate tensile strength of 905 MPa and 1320 MPa, respectively, and the total elongation of 45.6%, the mechanical properties are higher than those of the hot rolled samples and the one-stage warm rolled samples. The microstructural evolution during the two-stage warm rolling process and annealing are characterized and the strain partitioning behavior of the material is investigated. It is indicated that the outstanding mechanical properties and the strain hardening ability rely on the combination of the transformation induced plasticity (TRIP) effect and the hetero-deformation induced (HDI) hardening.