Recrystallization in non-conventional microstructures of 316L stainless steel produced via laser powder-bed fusion: effect of particle coarsening kinetics

Author(s)

Pinto, F. C. ; Aota, L. S. ; Souza Filho, I. R. ; Raabe, D. ; Sandim, H. R. Z.

• Document type: Journal article
• Source: Journal of Materials Science; v. 57, n. 21, p. 23-pg., 2022-01-20.

Abstract

Alloys processed by laser powder-bed fusion show distinct microstructures composed of dislocation cells, dispersed nanoparticles, and columnar grains. Upon post-build annealing, such alloys show sluggish recrystallization kinetics compared to the conventionally processed counterpart. To understand this behavior, AISI 316L stainless steel samples were constructed using the island scan strategy. Rhodonite-like (MnSiO3) nanoparticles and dislocation cells are found within weakly-textured grains in the as-built condition. Upon isothermal annealing at 1150 degrees C (up to 2880 min), the nucleation of recrystallization occurs along the center of the melt pool, where nuclei sites, high stored elastic energy, and local large misorientation are found in the as-built condition. The low value of the Avrami coefficient (n = 1.16) can be explained based on the non-random distribution of nucleation sites. The local interaction of the recrystallization front with nanoparticles speeds up their coarsening causing the decrease of the ZenerSmith pinning force. This allows the progression of recrystallization in LPBF alloys, although sluggish. These results allow us to understand the progress of recrystallization in LPBF 316L stainless steel, shedding light on the nucleation mechanisms and on the competition between driving and dragging pressures in non-conventional microstructures. They also help to understand the most relevant microstructural aspects applicable for tuning microstructures and designing new LPBF alloys. [GRAPHICS] . (AU)

• FAPESP's process: 19/19442-0 - Microstructural stability of AISI 316L stainless steel processed by selective laser melting using different scanning strategies
• Grantee: Leonardo Shoji Aota
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• FAPESP's process: 17/02485-2 - Characterization and evaluation of the microstructural stability of AISI 316L stainless steel processed via selective laser melting
• Grantee: Hugo Ricardo Zschommler Sandim
• Support Opportunities: Regular Research Grants