Novel austenitic Cr-Mn-Ni TWIP-steel with superior strength enabled by laser powder bed fusion – On the role of substrate temperatures

Abstract

• PBF-LB/M of the investigated steel dramatically improves the monotonic tensile behavior compared to the conventionally-cast material. • While UTS is nearly unaffected by a variation of substrate temperatures, the YS decreases, whereas work hardening and elongation at fracture are increased. • Such behaviour is well suited for robust PBF-LB/M processing, i.e. minor changes in the overall process do not promote pronounced changes in mechanical behaviour. • Irrespective of substrate temperature, the material exhibits an appealing strength-ductility combination In the present study, a novel austenitic stainless Cr-Mn-Ni steel was processed using laser-based powder bed fusion of metals (PBF-LB/M) at substrate plate temperatures ranging between 20 °C and 500 °C. Microstructure evolution was analysed by means of electron backscatter diffraction (EBSD). Different substrate plate temperatures lead to differences in microstructure evolution due to the prevailing cooling conditions and overall thermal history, eventually resulting in different hardening behavior under quasi-static tensile loading even if the general mechanical performance of the different conditions is very similar. From the results shown, it is deduced that the prevailing microstructures are a result of different internal stress states evolved during solidification, cooling and intrinsic heat treatment, respectively. The different internal stress states promote increased local orientation deviations within the grains, which can be rationalized by different dislocation densities. The monotonic strength of the steel in focus is outstanding compared with cold-rolled counterparts and data available in literature.