New insights on the origin of grain refinement in 316L additively manufactured alloys

Based on new experimental observations, a comprehensive analysis of factors influencing microstructure refinement in laser powder bed fusion additive manufacturing of 316L stainless steel components is presented. In contrast to existing hypotheses, the study reveals that neither the solidification mode nor the mere presence of nano-oxides in powders suffices to fully elucidate the observed grain refinement. Instead, this research highlights the intricate interplay between a strongly ferrite forming composition and the simultaneous presence of Mn-Si nano-oxides as essential contributors to the microstructure refinement process. The study explores the role of heterogeneous nucleation mechanism involving nano-oxides and provides fresh insights into the solidification mechanisms in laser powder bed fusion process, enhancing our understanding of microstructure control in laser powder bed fusion processes and offering novel perspectives for advanced materials engineering.