A high strength and low modulus metastable β Ti-12Mo-6Zr-2Fe alloy fabricated by laser powder bed fusion in-situ alloying

Biocompatible beta Ti-alloys with high strength and low modulus are of interest for additive manufacturing of biomedical implants. In this study, a metastable beta Ti-12Mo-6Zr-2Fe (TMZF) alloy with highly dense structure was successfully fabricated by laser powder bed fusion (LPBF) from low-cost elemental powders. The applied different scanning strategies (simple and chess scan), and post heat treatment can regulate both the texture and secondary phases. The formation of strong {100}< 001 > texture leads to the low elastic modulus of TMZF alloys, while nano-sized alpha '' phases induce significantly strengthening effect. The as-fabricated TMZF alloy via simple scanning strategy shows considerably high strength due to the high density of alpha '', omega phases and sessile dislocations, but it is brittle owing to the presence of omega phase. The TMZF alloy, manufactured using chess scanning strategy, possessed high yield strength of 1,026 MPa, low modulus of 85.7 GPa and good ductility of 12.7%. This results from its unique hierarchical microstructure containing alpha '' phases, heterogeneous grains and the formation of {100}< 001 > texture. After solution heat treatment, the specimens exhibit stronger {100} < 001 > texture, hence lower modulus of 70.9 GPa. High yield strength of 943 MPa was maintained due to the formation of plate-like alpha '' precipitates. The TMZF alloy fabricated by in-situ alloying based LPBF demonstrates comparable strength to that of Ti-6Al-4V alloy, but much lower elastic modulus, suggesting that it could be a potential candidate for some implant applications.

Automated summary

In this study, a metastable beta Ti-12Mo-6Zr-2Fe (TMZF) alloy with highly dense structure was successfully fabricated using laser powder bed fusion from low-cost elemental powders. The alloy exhibited low elastic modulus and high strength, but with a certain level of brittleness. After solution heat treatment, the alloy showed lower elastic modulus and maintained high strength. The TMZF alloy demonstrates comparable strength to Ti-6Al-4V alloy, but with much lower elastic modulus, making it a potential candidate for certain implant applications.