The Influence of Metastable Cellular Structure on Deformation Behavior in Laser Additively Manufactured 316L Stainless Steel

Metastable cellular structures (MCSs) play a crucial role for the mechanical performance in concentrated alloys during non-equilibrium solidification process. In this paper, typifying the heterogeneous 316L stainless steel by laser additive manufacturing (LAM) process, we examine the microstructures in cellular interiors and cellular boundaries in detail, and reveal the interactions of dislocations and twins with cellular boundaries. Highly ordered coherent precipitates present along the cellular boundary, resulting from spinodal decomposition by local chemical fluctuation. The co-existences of precipitates and high density of tangled dislocations at cellular boundaries serve as walls for extra hardening. Furthermore, local chemical fluctuation in MCSs inducing variation in stacking fault energy is another important factor for ductility enhancement. These findings shed light on possible routines to further alter nanostructures, including precipitates and dislocation structures, by tailoring local chemistry in MCSs during LAM.

Automated summary

Metastable cellular structures (MCSs) play a crucial role in determining the mechanical performance of concentrated alloys during non-equilibrium solidification. By examining the microstructures of cellular interiors and boundaries in 316L stainless steel produced through laser additive manufacturing (LAM), it was found that coherent precipitates and tangled dislocations at cellular boundaries can enhance material hardness, while local chemical fluctuation can improve ductility. These findings suggest potential strategies for altering nanostructures by manipulating local chemistry in MCSs during LAM.