Effects of recrystallization annealing temperature on carbide precipitation, microstructure, and mechanical properties in Fe–18Mn–0.6C–1.5Al TWIP steel

The microstructure, dimple structure, and mechanical properties of a cold-rolled Fe–18Mn–0.6C–1.5Al TWIP steel were investigated as a function of annealing temperature. The recrystallization started at 600 °C and finished at 700 °C for the holding time of 10 min. The coarsening rate of recrystallized grains was increased over about 840 °C and Rockwell hardness was greatly decreased between 800 and 900 °C, which shows a good agreement with the equilibrium dissolution temperature of M3C carbides. The reversion of the tensile strength occurred between 700 and 800 °C because of the carbide precipitation hardening. The precipitation-time-temperature diagram was generated by dilatometric tests, showing a nose temperature of 800 °C. The dimple size was decreased to 700 °C and then increased again with higher annealing temperature, having a strong proportional relationship with austenite grain size.