On the Damage Behavior of a 0.1C6Mn Medium-Mn Steel

The present work concentrates on the investigation of the damage behavior in the case of a batch annealed 0.1C6Mn medium-Mn steel as a function of intercritical annealing temperature. The variation of this important annealing parameter results in the formation of different microstructures, consisting of altering amounts of ferrite, martensite, and retained austenite. Martensite and retained austenite change not only in their volume fraction, but also in the grain size and composition, which implies a modification of their hardness and for the latter microstructural compound, varying chemical, and mechanical stability. Therefore, a detailed investigation of non-deformed and pre-strained microstructures is performed by means of scanning electron microscopy (SEM) and interrupted tensile testing is carried out to determine the retained austenite stability. To understand the macro- and micro-scale damage response of the investigated steel, tested tensile samples are analyzed with respect to their fracture behavior, as well as void appearance and their location within the microstructure. It is found that the stability of retained austenite and the presence of hard athermal martensite in the microstructure play the most important role, governing the overall damage behavior of the present medium-Mn steel.