Excellent mechanical properties and biocompatibility of Ti-15Mo alloy via interstitial nitrogen atoms

The insufficient tensile yield strength is a prominent deficiency for metastable biomedical titanium alloys from the clinical application perspective. In this study, we have reported a strategy to obtain excellent mechanical properties and biocompatibility of the Ti-15Mo alloy via interstitial nitrogen atoms. The results show that the addition of a trace amount of 0.1 wt% nitrogen atoms into Ti-15Mo alloy could significantly increase the tensile yield strength (YS) from 370 MPa to 995 MPa, while retaining a moderate elongation of 15.7% and an elastic modulus of 91.1 GPa. The obvious enhancement of tensile yield strength is mainly attributed to the grain refinement, twinning obstruction and dislocation pinning induced by interstitial nitrogen atoms. While the moderate plasticity is mainly because the introduction of nitrogen atoms could effectively inhibit the precipitation of nano-sized ω phases, thereby promoting remarkable dislocation slip. Moreover, the addition of interstitial nitrogen atoms could preserve the excellent in vitro biocompatibility of Ti-15Mo alloy, manifesting as elevated optical density (OD) values and increased filopodia and pseudopodia lengths. The insights derived from these findings are valuable for designing biomedical titanium alloys that possess excellent mechanical properties and biocompatibility.