Effect of Heat Treatment on Microstructural Evolution in Additively Manufactured 316L Stainless Steel

Abstract

316L stainless steel samples were prepared by selective laser melting (SLM) and annealed at 1000 °C for durations of between 1 and 6 h to investigate both the kinetics of microstructural evolution during heat treatment and the effect of annealing on mechanical properties. The as-printed materials contain a high density of oxide particles and dislocations, forming a dislocation cell substructure that shows high thermal stability during heat treatment. Moreover, coarsened oxide particles act as pinning barriers for moving dislocations and grain boundaries, thus extending the recovery and recrystallization process. The process of recrystallization can be effectively tracked by measuring the density of the low-angle misorientation boundaries associated with the oxide particles and dislocations, as characterized by high-resolution EBSD. The evolution of mechanical properties during annealing shows a strong relationship with the observed microstructural changes, suggesting possible optimization of strength and ductility of SLM-prepared metal samples by use of appropriate heat treatments.