High temperature flow instability and microstructural evolution of additive manufactured ۳۱۶L stainless steel produced by selective laser melting

This study examines the high-temperature deformation behavior and microstructural evolution of additive manufactured ۳۱۶L stainless steel produced by selective laser melting (SLM). Cylindrical specimens were fabricated using a ۳۰۰ W laser and subsequently subjected to hot compression tests at ۷۰۰ _x۰۰۱۷_۶C and ۱۰۰۰ _x۰۰۱۷_۶C under strain rates of ۰.۰۰۱ s_x۰۰۰۲_۰bd_x۰۰۰۰_b۹ and ۰.۱ s_x۰۰۰۲_۰bd_x۰۰۰۰_b۹. The as-built microstructure consisted of elongated columnar grains, serrated grain boundaries, and a cellular substructure, resulting from rapid solidification and directional heat flow during SLM. Flow stress analysis indicated that work hardening dominates the initial deformation stage, followed by softening due to dynamic recovery and recrystallization. At ۷۰۰ _x۰۰۱۷_۶C, continuous dynamic recrystallization (CDRX) was the primary softening mechanism, while discontinuous (DDRX) and geometrical (GDRX) recrystallization contributed to grain refinement. At ۱۰۰۰ _x۰۰۱۷_۶C, twinning and secondary-phase precipitation assisted microstructural stabilization and the formation of fine grains (<۲۰ _x۰۰۰۳_bc m). The hot-compressed samples retained a strong <۰۰۱> fiber texture and dense sub-boundary networks, leading to enhanced strength compared with conventionally processed ۳۱۶L. These findings provide insight into the interplay between SLM-induced substructures, deformation parameters, and recrystallization mechanisms governing the high-temperature performance of additive manufactured ۳۱۶L stainless steel.

کلیدواژه ها:

Selective laser melting (SLM) ، ۳۱۶L stainless steel ، Hot compression ، Flow behavior ، Dynamic recrystallization (DRX) ، Microstructural evolution ، Stacking fault energy (SFE) ، Texture development