Microstructure, mechanical properties, and deformation behaviour of LPBF 316L via post-heat treatment

Abstract

The study focused on analysing the changes in dislocation density and elemental segregation at cellular substructures, as well as the transformation of nano-oxide inclusions at different post-treatment temperatures, and their impacts on the strengthening mechanisms of 316L processed by laser powder bed fusion (LPBF). Additionally, through quasi in-situ tensile experiments, the plastic deformation and fracture behaviours of LPBF 316L after annealing at 900 °C were studied, revealing the reasons behind its high ductility. The results indicated that with increasing annealing temperatures, the nano-oxide inclusions coarsened and their density decreased due to the Ostwald ripening mechanism. The coarsened oxide particles act as barriers to moving dislocations and grain boundaries, thereby prolonging the recovery and recrystallization processes. This resulted in cellular substructures exhibiting high thermal stability. Consequently, the ultimate tensile strength of LPBF 316L after annealing at 900 °C is 651 MPa, with a total elongation of 62.3%, surpassing other studies.