Titanium alloys are vital for lightweight aerospace structures. Yet their application in micro-architected components using laser-powder bed fusion (L-PBF) is constrained by pronounced anisotropy and inadequate as-built strength, which typically requires post-processing. Here, we introduce an in-situ microalloying strategy using reactive micro-LPBF (µ-LPBF) for TA15 (Ti-6Al-2Zr-1Mo-1 V), supported by multiphysics modeling. This approach leverages nitrogen to simultaneously trigger isotropic grain refinement and activate synergistic strengthening mechanisms. Compared to the anisotropic pure Ar counterparts, optimized 5 vol% N2 specimens exhibit superior isotropic mechanical responses tailored for micro-bearing environments: achieving a record-breaking ultimate compressive strength of 2266 MPa (vs. 1827 MPa) and a hardness of 5.58 GPa (vs. 4.09 GPa), while maintaining a high strain-to-failure of 22.9%. The enhanced performance originates from the multifaceted role of nitrogen: increasing the molten pool’s energy absorptivity and inducing an obvious constitutional supercooling related to a high growth restriction factor for promoting a columnar-to-equiaxed transition of prior β-grains. At the atomic level, interstitial nitrogen promotes dislocation multiplication and in-situ polygonization into low-angle grain boundaries while stimulating deformation twinning. This coordinated “Solid Solution + Recovery” pathway enhances strength-plasticity synergy, providing a post-processing-free strategy for manufacturing high-performance, isotropic titanium components.
Huang et al. (Wed,) studied this question.
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