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

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 degrees 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 Luders strain. Temper-rolling is used for the ART-annealed specimens at 700 and 720 degrees 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 degrees C is noted at 1%, while the specimen annealed at 720 degrees 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 Luders band's formation.