Deformation behavior and recrystallization mechanism of a duplex stainless steel fabricated by laser powder bed fusion at high-temperature uniaxial tensile test

Abstract

Duplex stainless steels fabricated via laser powder bed fusion (LPBF) technology have demonstrated excellent strength and plasticity at room temperature, thus broadening their applications in complex structural components. However, their performance in extreme environments remains poorly understood. Consequently, this study systematically investigates the deformation behavior and recrystallization mechanisms of LPBF-fabricated duplex stainless steel upon high-temperature (1000 °C) uniaxial tensile testing. The results indicate that LPBF-fabricated duplex stainless steel has a yield strength of 64 ± 7 MPa and an elongation of 164 ± 12 %, which exceed those of a cast counterpart by 26 % and 100 %, respectively. This can be attributed to grain refinement and dislocation strengthening. During tensile deformation, the deformation degree increases in both ferrite and austenite. However, due to its higher stacking fault energy (SFE), ferrite undergoes more pronounced deformation whereby dislocations move through climb and cross-slip mechanisms. This leads to the formation of low-angle grain boundaries (LAGBs), which then migrate and gradually transform into high-angle grain boundaries (HAGBs), resulting in grain refinement. Because of the lower SFE in austenite, microstructural changes remain minimal. At the large deformation stage, the microstructural evolution is primarily driven by continuous dynamic recrystallization (CDRX), with an accelerated migration of grain boundaries in ferrite, where numerous LAGBs transform into HAGBs. In austenite, recrystallization occurs via discontinuous dynamic recrystallization (DDRX), where nucleation forms at the ferrite-austenite boundaries and subsequently grows into a new austenite phase. This study provides critical insights for microstructural control in LPBF-fabricated specimens during high-temperature deformation, such as hot isostatic pressing and localized weld repair.