Hot deformation behavior of a 3rd generation advanced high strength steel with a Medium-Mn content

Medium-Mn steels are one of the promising candidates to achieve the desired mechanical properties in the 3^rd generation of cold rolled advanced high strength steels (AHSS) for automotive applications. Their duplex microstructure consists of a ferritic matrix with a substantial amount of metastable retained austenite, which transforms to strain-induced martensite upon forming. This strengthening mechanism, well known as the TRansformation Induced Plasticity (TRIP) effect, provides the steel an excellent combination of high strength and elongation with a product of R_mxA₈₀ up to 30,000 MPa%. As hot rolling is one of the crucial steps during their production, the hot deformation behavior of Medium-Mn steels has to be thoroughly evaluated during their development stage. Therefore, the present contribution studied the hot deformation response of a 0.1 %C 5.5 %Mn steel by means of hot compression tests using a Gleeble® 3800 device. The influence of different deformation temperatures (900-1100°C) and strain rates (0.1-10 s^-1) on the stress-strain behavior was investigated. The flow curves were analyzed and corrected by the effects of adiabatic heating. Furthermore, the strain rate sensitivity m of the material was determined by evaluating stress values at different strain rates for given temperatures and strains. The m-values can be used to predict the deformation behavior of the material within the investigated range of parameters. Lastly, the hot working behavior of an alternative steel concept for a 3^rd Generation AHSS with significantly lower Mn-content was comparatively investigated.