Delayed deformation-induced martensite transformation and enhanced cryogenic tensile properties in laser additive manufactured 316L austenitic stainless steel

Abstract

Abstract The cellular dislocation structure is an important microstructure aspect in fusion-based laser metal additive manufactured (MAM) parts. Its role in increasing strength and ductility at room temperature (298 K) is a known phenomenon. In this work, we have shown that the cellular dislocation structure not only improves the strength but also dramatically increases the mechanical stability of the austenite and retards the deformation-induced martensite transformation (DIMT) of austenite at cryogenic temperature (77 K). The delayed and slow rate of DIMT led to an enhanced strength-ductility synergy in the direct energy deposited and selective laser melted 316 L stainless steel samples at 77 K compared to the wrought processed samples. The current study establishes the capability of MAM technologies in controlling the DIMT behavior and realizing materials with high strength and ductility combination.