In Situ Alloying of Ti-6Al-7Nb with Copper Using Laser Powder Bed Fusion

Titanium alloys are widely employed for biomedical implants due to their favourable combination of strength, corrosion resistance, and biocompatibility. A drawback, however, is the lack of intrinsic antibacterial functionality. In this study, Ti 6Al 7Nb was modified with varying copper (Cu) contents (1 wt.% – 9 wt.%) via in situ alloying during metal based laser powder bed fusion (PBF-LB/M) to investigate the processing behaviour, microstructural evolution, and mechanical properties. Powder mixtures were processed under systematically varied laser parameters, with densification, surface quality, and microstructure assessed by microscopy and X-ray diffraction, while hardness and tensile properties were characterised through mechanical testing. The results demonstrate that dense samples (> 99.9 %) can be achieved for all investigated copper amounts, although the homogeneity is strongly dependent on the process parameters. An increasing copper content promotes β-phase stabilisation, Ti₂Cu precipitation, and significant grain refinement with a transition from columnar to equiaxed structures. Hardness and yield strength increase nearly linearly with increasing copper content, while the ductility decreases sharply at ≥ 5 wt.% Cu due to intermetallic formation, hot cracking, and brittle fracture mechanisms. These findings highlight both the potential and the limitations of copper additions in Ti 6Al 7Nb processed by PBF LB/M. Overall, moderate additions of 1 wt.% – 3 wt.% Cu appear most promising, offering improved mechanical performance while preserving sufficient ductility and manufacturability for biomedical applications.