Microstructural Evolution and Mechanical Properties of a Medium-Manganese Steel Manufactured by Laser-Based Powder Bed Fusion of Metals

Medium-manganese steels (MMnS) represent novel third-generation advanced high-strength steels, which are characterized by Mn content between 3 and 12 wt% as well as a multiphase microstructure. These steels are well-known for outstanding combinations of high to ultrahigh strength at relatively high total elongation. Strength and ductility are significantly affected by the amount of retained austenite, its stability, and the related transformation-induced plasticity. Due to the possibility of microstructure design, laser-based powder bed fusion of metals (PBF-LB/M) is a promising processing method to tailor the mechanical performance of MMnS. In the present study, a Fe–12Mn–0.2C MMnS is manufactured by PBF-LB/M using blended powder as well as pre-alloyed powder to investigate the applicability of rapid alloy development. Various scanning speeds are used to determine the influence of energy deposition rate on microstructure and mechanical properties. Microstructural analysis of the different as-built conditions is carried out by optical and scanning electron microscopy, X-ray diffraction, and electron backscatter diffraction. The feasibility of using blended powder instead of atomized powder for preliminary experiments on PBF-LB/M-produced MMnS is discussed. In addition, a significant influence of process parameters on the resulting austenite fraction as well as strength and ductility for the investigated material is revealed.