Influence of partial replacement of Si by Al on the change of phase fraction during heat treatment of TRIP steels

We have investigated the change of phase fraction during heat treatment for Fe–C–Mn–Si and Fe–C–Mn–Si–Al transformation-induced plasticity (TRIP) steels. Combined metallographic and dilatometric analysis reveals that partial replacement of Si with Al enhances ferrite formation from austenite during subsequent heat treatment after intercritical annealing. The increase in ferrite fraction by Al addition is ascribed to the acceleration of the growth of intercritical ferrite as well as the formation of bainitic ferrite.