Additive friction stir deposition of Fe-Cr-Ni transformative alloy

• AFSD process successfully enabled the printability of transformative Fe-Cr-Ni alloy. • Metastable austenite exhibited notable work hardening driven by transformation-induced plasticity. • AFSD achieved an excellent strength-ductility synergy compared to conventional counterparts. • Layer-dependent variation in microstructural, mechanical behavior, strengthening mechanisms. • Dislocation-based Kocks-Mecking model corelated effectively with the observed work hardening behavior. A comprehensive microstructure-oriented mechanical property investigation of Fe-Cr-Ni alloy manufactured via additive friction stir deposition (AFSD) was conducted. This study aims to design a comprehensive understanding of the spatial correlation between microstructure and mechanical properties as a function of the build height. Multiple reheating cycles that exist during the layer-by-layer deposition enabled microstructural variation from a single-phase BCC (bottom layer) to a dual-phase microstructure (top layer) consisting of a secondary FCC phase. The enhancement in work-hardening response in the top layer was driven from concurrent transformation-induced plasticity (TRIP) and deformation twinning mechanisms activated within the metastable austenite, yielding an excellent strength-ductility synergy. A mechanistic understanding of strain-hardening behavior was achieved using the dislocation-based Kocks-Mecking model. The primary constituent of the texture, specifically modified brass, resulted from the deformation-induced martensitic transformation. These insights provide a path for designing enhanced mechanical properties by tuning dual phase transformative microstructure.