The developments of cold-rolled TRIP-assisted multiphase steels. Low silicon TRIP-assisted multiphase steels

TRIP-assisted-multiphase steels are newly developed steels exhibiting an improved balance of strength and ductility very well adapted for the automotive industry. In order to allow the retention of austenite, the steels studied up to now contained high levels of silicon incompatible with the industrial practice. This study shows how the combination of both a composite strengthening effect and the TRIP effect can improve the mechanical properties of a cold-rolled 0.16wt%C-1.3wt%Mn steel containing only 0.4wt% of silicon. A complete characterisation of the bainite transformation and of the resulting microstructures, tensile properties and mechanical stability of retained austenite has allowed the determination of the factors responsible for the enhanced balance of strength and ductility of this steel well adapted for automotive applications.