Comparative analysis of microstructure and mechanical properties in FeMnAlNi alloys fabricated via casting and additive manufacturing

This study provides a comprehensive analysis of FeMnAlNi alloys fabricated via casting, laser-based directed energy deposition (DED-LB), and powder bed fusion-laser beam (PBF-LB) techniques, highlighting the profound impact of manufacturing processes on their microstructural characteristics and mechanical properties. The investigation reveals distinct two-phase distributions, with PBF-LB samples retaining the high-temperature alpha-phase due to rapid cooling, contrasting with the gamma-phase predominance in as-cast and DED-LB samples. Notably, PBF-LB samples also exhibit fine gamma ' martensites, likely a result of stress-induced martensitic transformation. Mechanical testing shows significant variations across the samples: as-cast and DED-LB samples demonstrate similar microhardness values (211 +/- 22 and 209 +/- 7 HV0.2, respectively), while PBF-LB samples exhibit higher microhardness (321 +/- 9 HV0.2) due to the dominance of alpha-phase. Specifically, the DED-LB samples demonstrate elongation exceeding 50 %, with a notable improvement in ductility compared to the as-cast samples. The Kurdjumov-Sachs orientation relationship between alpha-phase and gamma/gamma '-phases is found. These insights reveal that considerable work remains to be done, including exploring post-processing heat treatments, which have the potential to induce superelasticity in DED-LB samples and further enhance the application potential of FeMnAlNi alloys in advanced engineering fields.