Effect of the work-hardening of retained austenite on the martensitic transformation in a trip-aided steel

This study deals with the hot deformation of TRIP-assisted multiphase steels. These steels consist typically of bainite and retained austenite grains dispersed in a ferritic matrix. The austenite. which is metastable at room temperature, transforms to martensite during straining, bringing about the TRIP effect, which improves the strength - ductility balance of these steels. This work investigates the effect of a prior deformation in the intercritical temperature range on the mechanical properties and work hardening behaviour of these TRIP-assisted multiphase steels. Several deformation levels in the ferrite-austenite domain were applied during the thermo-mechanical scheme. Results show that work-hardening is strongly enhanced when the specimens were sufficiently deformed in the intercritical temperature range. This study also shows that the beneficial influence of the prior deformation is more related to the TRIP phenomenon than to the strain-hardening of the ferritic matrix. These experiments prove that a displacive transformation such as the martensitic transformation is highly influenced by the dislocation density within the parent phase.