Due to their diverse properties and their low price compared to many other metallic alloys, steels are the material of choice for countless applications in a wide range of areas, such as for numerous automotive body components. Steels are known to exhibit the typical strength-formability discrepancy, i.e. either strong and hard or vice-versa. The manganese-containing steels can be counted as an exception with their combination of high tensile strength and elongation at break. The different manganese-containing steels have in common that manganese is substitutionally dissolved in iron and the manganese content is used specifically to stabilize the austenite phase at room temperature. MMnS achieve higher strengths and sufficient plasticity and their mechanical properties cab further customized by heat treatment and thus the resulting microstructure and local chemical composition.

Laser-based additive manufacturing (AM) processes have become increasingly important in recent years and today represent an important technology for the production of highly complex components, such as energy-absorbing, density-reduced lattice structures made from a wide variety of metallic alloys. Although it was the focus of many studies before, MMnSs were not investigated for AM route. Therefore, a profound understanding of the understanding of the fundamental process-microstructure- property relationships in high-performance metallic materials is imperative for exploring the full potential of additive manufacturing, both the metallurgical as well as the technological aspects the microstructure development.

This study focuses on the effect of various laser scanning speeds in PBF-LB/M on the microstructure evolution of a medium manganese steel during solidification and further cooling. This effect was analysed by eludiciating the factors influencing austenite stability and the formation mechanisms of α'-martensite.  Additionally, we integrate these empirical results with various computational techniques, including CALPHAD, phase field, and finite element methods, to establish a robust understanding of the material's behavior at the micrometer scale. Furthermore, we conduct a comparative analysis of primary austenite grains and retained austenite, constructing a timeline to elucidate the progression of austenite grains and uncover critical insights into the martensitic transformation process.