Process-induced micromechanics variations in additively manufactured 316 stainless steel characterised by quasi-in-situ EBSD

The strength-ductility trade-off remains a critical challenge in additively manufactured stainless steels due to their process-induced microstructures. In this study, type 316 stainless steel (SS316) was fabricated via a novel metal additive manufacturing technique employing powder sheets (MAPS), demonstrating exceptional strength with considerable ductility. To elucidate the mechanisms underlying this performance, quasi-in-situ electron backscatter diffraction (EBSD) was employed to monitor the microstructural evolution and deformation behaviour of SS316 produced by MAPS in comparison with laser powder bed fusion (LPBF). LPBF exhibits extensive deformation twinning that facilitates broad strain accommodation with sustained hardening, whereas MAPS shows dense dislocation storage within cellular substructures, leading to pronounced strain hardening and superior strength. The limited twinning activation in MAPS constrains strain redistribution, localising plasticity along cellular subgrain boundaries. The interplay between dislocation-dominated hardening and twinning-limited plasticity provides MAPS-processed SS316 with enhanced mechanical performance and highlights the importance of processing strategy in tailoring deformation pathways.