Effect of Retained Austenite on Mechanical Properties of 5% Mn Steel

Recently, 5% Mn steel has been focused on as one of the promising candidates for third generation AHSS by showing an excellent TS-El relationship. The excellent TS-El relationship is brought about by a large volume fraction of retained austenite through the enrichment of austenite stabilizing elements such as C and Mn in reverted austenite. The effect of the microstructure of mother hot band on the changes in microstructure and mechanical properties was compared with the intercritical annealing time in this study. The steel containing about 10% of retained austenite in a mother hot band exhibited a higher volume fraction of retained austenite and higher strength. On the other hand, the steel which did not contain retained austenite in a mother hot band exhibited excellent strength-elongation combination. The difference of work hardening behavior in these steels was analyzed and thought to be brought about by the difference of transformation behavior during deformation determined by the stability of retained austenite affected by Mn concentration.