Dependency of recrystallization kinetics on the solidification microstructure of 316L stainless steel processed by laser powder bed fusion (LPBF)

Abstract

In this study, the recrystallization kinetics of two 316 L stainless steels produced by Laser Powder-Bed Fusion (LPBF) were compared. The as-built microstructures of the studied materials differed by their grain size, their grain boundary character distributions, and their populations of nanoprecipitates. Strong differences in their recrystallization kinetics were observed; they were attributed to a delayed nucleation in the steel exhibiting the finer grains, the lower density of low-angle boundaries (LAB), and the higher volume fraction of precipitates. This work shows that a high density of LABs stemming from the solidification stage in the LPBF process promotes recrystallization by locally increasing the stored energy close to grain boundaries, and hence the formation of recrystallization nuclei. The design of low-LAB microstructures could thus lead to higher stability at high temperatures. • Recrystallization kinetics are heavily influenced by the as-built microstructure. • Kinetics are not affected by a second-phase particles volume fraction increase. • Low angle boundaries promotes the formation of recrystallization nuclei.