Optimization of Laser Powder Bed Fusion Parameters for Ti-13Nb-13Zr: The Interplay Between Energy Density, Surface Integrity, and Nanomechanical Performance

Laser Powder Bed Fusion (LPBF) offers a transformative route for manufacturing patient-specific biomedical components from low-modulus β-type titanium alloys. In this work, the processability of Ti-13Nb-13Zr was assessed through a VED-based approach, focusing on how energy input influences densification, surface topography, and local nanomechanical response across a processing window of 38.65-87.72 J/mm³. Relative density measurements, surface profilometry, and nanoindentation were used to identify the processing conditions that provide the most favorable balance between build quality and mechanical performance. The results show that near-full densification, ranging from 98.71% to 99.55%, can be achieved within the investigated LPBF window. The highest relative density was obtained at an intermediate VED of 72.46 J/mm³, indicating that increasing energy input alone does not necessarily lead to optimal densification. Surface quality improved markedly at higher VED, with Ra decreasing from 10.687 μm to 1.596 μm and Rz from 52.588 μm to 9.342 μm, suggesting enhanced melt pool wetting and surface consolidation. Nanoindentation revealed an increase in hardness from 3.97 GPa to 4.41 GPa with increasing VED. However, the intermediate-VED condition exhibited the lowest reduced modulus and the highest H/Er and H³/Er² ratios, indicating a favorable combination of mechanical compliance and resistance to local deformation. Overall, these findings show that the most promising LPBF condition for Ti-13Nb-13Zr is not governed solely by maximum energy input. Instead, an intermediate VED provides the best density nanomechanical balance, while higher VED mainly benefits surface finish.