Interplay between deformation behavior and mechanical properties of intercritically annealed and tempered medium-manganese transformation-induced plasticity steel

We elucidate the mechanistic contribution of the interplay between microstructural constituents and plastic deformation behavior of a hot rolled Fe-0.18C-10.62Mn-4.06Al-0.03Nb transformation-induced plasticity (TRIP) steel that was characterized by excellent tensile elongation (TE) of 48%, ultimate tensile strength (UTS) of 1012 MPa, and yield ratio of 0.58. The excellent mechanical properties were a cumulative contribution of TRIP effect, discontinuous TRIP effect, and the cooperative deformation of austenite, δ-ferrite, and α-ferrite, such that the austenite stability dictated the ultimate mechanical properties and the dynamic composite nature of the three stages of work hardening. More importantly, the austenite stability was governed by the combination of intercritical annealing and tempering treatment, when partitioning of carbon and manganese took place; an aspect supported by the simulation of intercritical annealing condition via DICTRA. The study underscores the significance of intercritical annealing in conjunction with tempering as a viable route to obtain the desired mechanical properties in the new generation of advanced high strength steels (TRIP steels).