The influence of zirconium content on the microstructure, mechanical properties, and biocompatibility of in-situ alloying Ti-Nb-Ta based β alloys processed by selective laser melting.

This study investigates Ti-Nb-Ta based β alloys with different zirconium additions (0, 5, 9 wt%) manufactured by SLM. A low level of as-fabricated defects is obtained: the relative density of TNT (Z) alloys is >99.97% with the keyhole size in a range of 3-20 μm. BF TEM images combining SAD patterns of TNT(Z) alloys show single β phase obtained inside the beta matrix; BF-STEM images reveal potential nano-scale grain boundary alpha phase precipitation. Zirconium functions as a neutral element in these high β-stabilized Ti-Nb-Ta based alloys. An increase in Vickers hardness and UTS caused by zirconium additions is observed, which is explained by beta grain refinement because higher degree of undercooling occurs. Corrosion ions of TNT(Z) alloys released from immersion testing at each time intervals show extremely small concentrations (<10 μg/L). It indicated that good biocompatibility during culture with the negligible corrosion ions. High strength-to-modulus ratio β Ti alloys together with excellent biological response show their prospect for biomedical applications.