New M_s-formula for exact microstructural prediction of modern 3^rd generation AHSS chemistries

The exact adjustment of the individual microstructural constituents, in particular the optimum volume fraction of metastable retained austenite (RA), is imperative in case of the 3^rd generation advanced high strength steels (AHSS). Moreover, it is of vital importance to avoid the formation of fresh martensite (α’) upon final cooling, otherwise the resulting mechanical properties of these novel steel grades will be pronouncedly deteriorated. Therefore, an accurate estimation of the martensite start (M_s) temperature is essential for modelling and development of this steel group. In this context, the present contribution proposes a new relation for the M_s temperature prediction with a remarkably wide composition range based on the 3^rd generation AHSS chemistries. Moreover, the new M_s formula allows for an accurate determination of the M_s temperature for both, extremely low and very high C contents, which is not the case in any M_s formula known from literature.