Additive manufacturing of anti-bacterial and low-cost Ti–Mo(–Ag) alloys using elemental powders through in situ laser alloying

The Ti–15Mo alloy has become a widely recognized biomedical Ti alloy due to its excellent properties, including a low Young’s modulus that is close to that of a human bone. Selective laser melting (SLM) additive manufacturing (AM) offers both advanced manufacturing capabilities to the processing of the alloy and the potential to make customized implants. The feedstock cost of pre-alloyed Ti–15Mo powder, however, is high, like that of many other Ti alloys, and can be a major obstacle to the wider application of the AM technique. This study focused on mitigating this problem by using an in situ laser alloying approach, wherein a low-cost hydride-dehydrate (HDH) Ti powder was mechanically mixed with elemental Mo powder to form a composite powder feedstock (i.e., Ti + Mo). The Ti–15Mo alloy could be printed with a high relative density (~ 99.76%). A finite element simulation was performed to study the melt pool during the SLM process with subsequent detailed discussions to understand the in situ alloying mechanism. Mechanical property indicates the as-printed Ti–15Mo has high strength (~ 1170 MPa) but low ductility, while the latter has been much improved by introducing a merely 0.2 wt% of yttrium (Y). Based on the optimized Ti–15Mo–0.2Y alloy with a strength of ~ 1300 MPa and a modulus of ~ 85 GPa, different amounts of elemental Ag powder were further alloyed in situ to acquire antibacterial properties. Compared with the antibacterial activity of the control group, that of the final material, i.e., in situ laser alloyed Ti–15Mo–0.2Y–2.5Ag, reached 92–95%; the addition of Ag had a minimal effect on the cell viability. In vivo experiments demonstrated the Ag-containing alloys to exhibit good biocompatibility. Graphical Abstract