The Effect of Annealing Temperature and Temper‐Rolling on Microstructure, Mechanical Properties, and Lüders Strain of Fe–0.25C–5.9Mn–1.0Al–1.57Si Medium Mn Steel

Abstract

This study investigates the effect of austenite reverted transformation (ART) annealing temperature and temper‐rolling on the microstructure, mechanical properties, and deformation behaviors of cold‐rolled Fe–0.25C–5.9Mn–1.0Al–1.57Si transformation‐induced plasticity (TRIP) steel. The cold‐rolled steel annealed at 700 °C demonstrates excellent mechanical properties. The ultimate tensile strength, total elongation, and product of strength and elongation are observed as 1212 MPa, 31.8%, and 38.6 GPa%, respectively. The excellent combination of strength and ductility is related to the discontinuous TRIP effect; still, an inhomogeneous deformation is observed during tensile deformation, known as the Lüders strain. Temper‐rolling is used for the ART‐annealed specimens at 700 and 720 °C, and yield point elongation decreases when temper‐rolling reduction increases. When the temper‐rolling reduction increases by 8%, the yield point elongation of the specimen annealed at 700 °C is noted at 1%, while the specimen annealed at 720 °C exhibits continuous yielding. The strain‐induced martensite transformation and increased dislocation density in the ferritic matrix improve the early‐stage strain hardening rate, thus suppressing the Lüders band's formation.