Investigations on martensite formation in CrMnNi-TRIP steels

Abstract

A new generation of high alloyed cast CrMnNi-TRIP-steels was developed exhibiting high strength (UTS) as well as high uniform elongation for a maximum of energy-absorption. The nature of the high elongation is the formation of α'-martensite in the most deformed areas of the metastable austenitic steel, so that necking is delayed. Because of the low stacking fault energy, due to the high alloying concept, deformation is mainly accompanied by the development of deformation bands in coarse austenitic grains and further the formation of α'-martensite. Within this study, stress-strain curves will be evaluated by the corresponding microstructure information obtained by LOM, SEM and EBSD examinations. The formation of α'-martensite is discussed for tensile and compressive loading at room temperature. The arrangement of martensite within the microstructure and the local deformation dependency of the α'-martensite fraction is considered. Martensite kinetics will be presented for interrupted deformation tests, determined via magnetic balance (MS), EBSD and light optical metallography (LOM).