Design of high-manganese steels for additive manufacturing applications with energy-absorption functionality

Abstract

High-manganese steels (HMnS) are alloys with outstanding mechanical properties, but their application is inhibited by inherent limitations in conventional processing. Additive manufacturing (AM) provides an alternative to make use of the unique properties of HMnS due to strongly differing processing conditions. However, no established methodology exists currently to tailor metallic alloys specifically for AM. Therefore, a methodology combining theoretical and experimental screening was used to design a HMnS specifically suited for AM. First, different chemical compositions were screened with thermodynamics-based stacking fault energy (SFE) maps to predict the activation of transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP). For experimental screening, selected X30MnAl23-# alloys (with # ≤ 2 wt%) were produced by laser metal deposition (LMD). The metal physical mechanisms active during solidification and plastic deformation were identified by multiscale microstructure characterization (XRD, OM, SEM, EBSD, EDX, EPMA, APT) and tensile testing. Finally, two steels with the highest work-hardening capacity and formability were applied in lattice structures produced by selective laser melting (SLM) and compared to benchmark 316L steel. The correlation of AM-specific features of HMnS and their effect on deformation behavior as well as the applicability of the used methodology are discussed to illustrate the effectiveness of the chosen approach toward the development of high performance materials for AM. Keywords: Fe-Mn-Al-C, Solidification, Deformation, Thermodynamics, Additive manufacturing