Achieving superior performance of wire-directed energy deposited 316L stainless steel through the synergic effect of in-process high-pressure rolling and post-heat treatment

Abstract

316L austenitic stainless steel manufactured by wire-direct energy deposition (w-DED) typically exhibits coarse columnar solidification microstructures and pronounced anisotropy, which significantly limits its structural performance and engineering applicability. In this work, a cold high-pressure inter-layer rolling (HPR) strategy combined with post-deposition solution heat treatment is proposed as an effective and industrially viable thermo-mechanical route for microstructure and property control. Cold HPR introduces a large plastic strain at a low and well-controlled inter-pass temperature. This suppresses dynamic recovery during deposition and allows substantial stored strain energy to accumulate. As a result, the as-deposited microstructure evolves from a solidification-dominated state to a deformation-controlled state. The rolled components show pronounced deformation of the γ-austenite and fragmentation of the δ-ferrite. This deformation is accompanied by an increased fraction of low-angle grain boundaries and a higher dislocation density, which leads to significant strengthening. Subsequent heat treatment activates extensive static recrystallisation in the rolled samples. Fine equiaxed γ-austenite grains with high fractions of high-angle and Σ3 boundaries are formed, together with a strongly weakened crystallographic texture. This rolling + heat treatment synergy enables a broad and continuous mechanical property window and delivers a superior strength-ductility balance. The achieved performance surpasses most reported additively manufactured and wrought counterparts. Overall, the proposed cold HPR + heat treatment route provides a practical and flexible pathway for tailoring the performance of large-scale w-DED 316L components.