Influence of dislocation cell on the thermomechanical stability of 316 L fabricated by laser powder bed fusion

In engineering applications where high temperatures are a concern, the quest for structural components exhibiting robust thermomechanical stability is paramount. This study delves into the thermomechanical stability of 316 L steel fabricated via laser powder bed fusion (LPBF), with a particular emphasis on understanding the role of dislocation cell structures. In this study, deliberate rolling deformation followed by annealing at elevated temperatures was performed. The rolling deformation resulted in the introduction of dislocations and deformation twins in LPBF 316 L. Notably, deformation twins were observable in LPBF 316 L annealed at 800 °C, but they vanished at 1050 °C. Dislocation recovery was evident in pre-deformed samples following annealing at both temperatures. However, even after annealing at 800 °C, the grain and dislocation cell structures of heavily pre-deformed samples exhibited considerable stability. Conversely, during annealing at 1050 °C, substantial recrystallization occurred in pre-deformed samples, with the degree of recrystallization correlating with the extent of plastic deformation. In contrast, the grain structure of non-deformed samples remained unchanged after annealing at 1050 °C. This suggests that the dislocations induced by rolling serves as dislocation-stored energy, thus promoting recrystallization. The enduring stability observed in the grain and cell structures of heavily pre-deformed samples at 800 °C, as well as the high stability of these structures in non-deformed samples at 1050 °C, can be attributed to the presence of dislocation cell structure with low-energy contributing to retarded recrystallization.