Strain Rate Effect on Microstructural Evolution and Deformation Behavior of Medium‐Mn Transformation‐Induced Plasticity Steels

Abstract

Herein, the effect of strain rate (10−4–10−1 s−1) on the microstructural evolution and deformation behavior of medium‐Mn transformation‐induced plasticity (TRIP) steels is investigated. The steel after intercritical annealing exhibits an austenite–martensite–ferrite triplex microstructure with a relatively high austenite fraction (66.1%). A negative strain rate dependence of ultimate tensile strength (UTS) and significant serrated behavior are found during the room temperature tensile test. The total elongation (TE) attains a maximum value of 32.0% at the strain rate of 10−2 s−1 and then decreases with increasing strain rate. The evolution of strain‐induced martensitic transformation (SIMT) as a function of strain rate is analyzed considering the adiabatic heating during deformation. The different degrees of SIMT under different strain rates lead to a fracture transition between quasicleavage fracture and ductile fracture. The delamination cracks originating from the interface of martensite and austenite are closely related with the quantity and the local strain of the martensite–austenite interface.