Medium-manganese steel are of significant industrial interest due to their excellent strength–ductility balance arising from activation of transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP). In Directed Energy Deposition process, however, high heat input frequently induces elemental evaporation and segregation, resulting in deformation behavior distinct from conventionally casting material. To clarify the deformation behavior, an austenitic medium manganese steel with a composition of Fe-10Mn-10Cr-3Ni (wt%) was fabricated using the DED process. The EDS results revealed pronounced Mn and Cr segregation along cell boundaries. During tensile deformation, BCC phases formed preferentially inside the cells. and TEM. EBSD analysis of tensile-deformed samples confirmed the simultaneous occurrence of TRIP and TWIP within the cellular structure. LUR testing further demonstrated that the TRIP effect was more dominant in specimens manufactured with 600 W than in those produced with 300 W. This difference is attributed to elemental segregation and Mn evaporation which depend on heat input, which were confirmed through ICP analysis.
