In-situ alloying of Ti-6Al-7Nb with copper using laser powder bed fusion for enhanced biocompatibility in permanent implants

Laser Powder Bed Fusion (L-PBF) enables the development of novel materials through in-situ alloying directly from elemental or mixed powders, which presents a significant advantage in the development of new alloys. However, in-situ alloying presents element-specific difficulties, such as different melting points and the tendency to form brittle phases due to incomplete mixing. These challenges can be overcome by optimising the particle size distribution of the starting powders and by using multiple exposures in the process, resulting in better mixing and a finer microstructure. In addition, to achieve dense bulk materials and reduce edge effects, it is necessary to adjust process parameters such as laser power, scan speed and hatch distance for the powder mixtures. Research has shown that the in-situ alloying of Ti-6Al-7Nb and copper results in a significantly refined microstructure and improved mechanical properties compared to the base material. Furthermore, this alloy system combines the proven biocompatibility and mechanical reliability of Ti-6Al-7Nb with the known antibacterial properties of copper, offering a promising alternative to Ti-6Al-4V by eliminating the potential cytotoxicity of vanadium. The initial low elongation at break was significantly improved by post-process heat treatment, allowing the mechanical properties to be tailored to different clinical needs. In addition, the introduction of copper provides an antibacterial effect while maintaining good cytocompatibility and improved bone growth into the implant. This contribution provides insight into the difficulties of in-situ alloying of Ti-6Al-7Nb+xCu by L-PBF. Our results show how both mechanical performance and biological functionality can be optimised by adjusting process and alloy parameters, supporting the development of next-generation infection-resistant metallic implants for biomedical applications. To investigate the influence of copper, a CALPHAD-approach was used and EDX, EBSD, XRD and LOM investigations were performed, which were contextualised with experimental results from tensile tests, hardness measurements and corrosion investigations.