• In-situ boron microalloying during LPBF effectively refines the grain structure of Ti-6Al-4V, transforming coarse columnar grains into fine equiaxed grains.
• The addition of 0.5 wt% B results in a 25% increase in yield strength and a 15% improvement in ductility, without compromising hardness.
• TiB precipitates formed during solidification act as heterogeneous nucleation sites, promoting grain refinement and enhancing mechanical performance.
• This approach offers a scalable and cost-effective method to improve the mechanical properties of additively manufactured titanium alloys for aerospace and biomedical applications.