Influence of annealing temperature on microstructure and tensile property of cold-rolled Fe-0.2C-11Mn-6Al steel

To fully realize the potential of austenite characterized by strip-like and equiaxed structure and enhance the comprehensive mechanical properties of medium-Mn steel, the as-hot-rolled Fe-0.2C-11Mn-6Al steel was subjected to cold roll annealing to refine the grain size. The ultimate tensile strength of the cold-rolled steel annealed at 650 °C was significantly enhanced, while the total elongation was markedly decreased. The variation in tensile properties of the annealed cold-rolled steel was due to weakening of transformation induced plasticity (TRIP) effect and enhanced twinning induced plasticity (TWIP) effect with increase in quenching temperature. Furthermore, austenite had two different morphologies, strip-like and granular. Though the grain size of granular austenite increased with increased annealing temperature, the austenite stability increased with increase in quenching temperature, which is contrary to the expectations. This is attributed to refinement of large austenite strips induced by recrystallization.