Plastic Stability of Retained Austenite in the Cold-rolled 0.14%C-1.9%Si-1.7%Mn Sheet Steel

Mechanical properties of a 0.14%C-1.9%Si-1.7%Mn TRIP steel have been studied especially from the aspect of the plastic stability of retained austenite which was varied by changing bainite transformation time at 400°C. The plastic stability of retained austenite and the strength-ductility balance at room temperature are improved with the increase in C content in retained austenite after optimizing the bainite transformation time in the continuous annealing process. Martensitic transformation can occur from the plastically unstable retained austenite with low C content. The kinetics model for deformation-induced martensitic transformation explains the experimentally obtained change in volume fraction of retained austenite with plastic strain in terms of the C content in retained austenite.