Tailoring mechanical properties and corrosion resistance via recrystallization-induced microstructural control in LPBF-fabricated IN718

• Twin-rich equiaxed IN718 exhibits ∼3× larger grains and ∼64% Σ3 twin boundaries. • Most Laves/δ phases are dissolved, leaving nano-precipitates at twin boundaries. • 6.8% lower YS but higher strain hardening and +25% elongation at room temperature. • Similar trends at 650 °C confirm persistent influence of initial grain morphology. • Fewer corrosion scales in boiling 5% HCl immersion indicate slower degradation. This work establishes a grain boundary engineering strategy for laser powder bed fused Inconel 718 by exploiting recrystallization-induced microstructural co-evolution. Columnar as-built and recrystallized twin-rich equiaxed microstructures are generated from a single LPBF build through tailored solution treatment, enabling a controlled comparison of grain morphology, Σ3 twin fraction, dislocation density, and Laves/δ phase segregation. The equiaxed condition, with isotropic ∼56.5 µm grains and 63.8% Σ3 boundaries, shows strongly reduced geometrically necessary dislocation density and Laves phase content relative to the columnar condition with ∼17.4 µm elongated grains. Furthermore, only nano-sized precipitates occur at twin boundaries, while the general high-angle grain boundaries are enriched in large Laves phases. This microstructural combination delivers favourable balanced properties, with only 6.8% loss in yield strength but greater strain hardening and 25.1% enhanced elongation at room temperature. Similar trends observed at 650 °C underscore the continued influence of initial microstructures. In aggressive boiling oxidizing solutions, the equiaxed microstructure forms significantly fewer Nb/Mo-rich scales and exhibits a ∼33% lower corrosion rate (39.24 vs 52.21 g/m 2 ·h). The results show that recrystallization-driven twin network formation and Laves depletion provide an effective route to optimize mechanical performance and corrosion resistance in LPBF-fabricated IN718 simultaneously.