A novel pathway to realize the columnar-to-equiaxed transition and mechanical anisotropy suppression in SEBM of 316L

To address the critical challenge of anisotropy in metal additive manufacturing (AM), a novel strategy has been proposed in this work using SEBM-fabricated 316L stainless steel to achieve the columnar-to-equiaxed transition (CET) and suppress mechanical anisotropy. By simultaneously reducing the power and speed, the thermal gradient (G) and solidification rate (R) were tuned under the constant Volumetric Energy Density (VED). Associating with in-situ recrystallization activated by the sustained thermal dwell at ∼800 °C, CET can be achieved in SEBM 316L. This yields a microstructure with a pronounced increase in equiaxed fraction (13.9 % → 81.9 %) and strong texture weakening (Multiple of Uniform Distribution, MUD 23.75 → 3.01). Consequently, the strength–ductility synergy (Ultimate Tensile Strength, UTS ≈ 603 MPa; Elongation, EL ≈ 71 %) can be realized as well as the near-isotropic mechanical behavior (Index of Plane Anisotropy, IPA ≈ 1.75 %–1.79 %). This study demonstrates that CET can be realized through the combined effect of solidification control and in-situ recrystallization in SEBM, thereby suppressing anisotropy in both microstructure and mechanical performance. The findings can offer transferable guidance for microstructural design and process–structure–property optimization in other alloys AM systems, including nickel-based and other alloys. • Transferable columnar-to-equiaxed transition and anisotropy suppression were achieved in Selective Electron Beam Melting. • Solidification and in-situ recrystallization synergize to facilitate the microstructure evolution. • Fine equiaxed grains and weakened texture were achieved through simple one-step fabrication. • Strength–ductility–anisotropy trade-off was effectively broken in additively manufactured stainless steel.