The TRIP Effect and Its Application in Cold Formable Sheet Steels

The Transformation-Induced-Plasticity (TRIP) effect is used for enhancing the formability of cold formable sheet steels. While the first observation of this phenomenon dates back to the 1930's, the industrial usage of the TRIP steels started after 1950. First fully austenitic steels, later on multiphase steels have been developed with a meta-stable austenitic phase that can transform stress-assisted or strain-induced into ϵ- or α′-martensite during deformation. The historic development, the principles of the TRIP effect, and the different groups of steels using the TRIP effect are described. For the already commercialized TRIP steels, characteristic chemical compositions and microstructures are discussed; the requirements for the process design as well as new annealing concepts after cold rolling are explained.