Tailoring β-Ti based shape memory alloy with the exceptional mechanical and functional properties towards biomedical bone implants application

In the present study, the interstitial hydrogen (H) atoms were introduced as beta-stabilizing element to tailor the microstructure, martensitic phase transition, and functional properties of Ti-V-Al shape memory alloys for biomedical applications. The results revealed that the addition of interstitial H atoms into Ti-V-Al shape memory alloys induced the transition from a single alpha"" martensite to the coexistence of beta parent phase and alpha phase, regardless of H content. Moreover, the amount of alpha phase firstly increases and then decreases in the present Ti-V-Al based shape memory alloy with H content increasing. Besides, H addition resulted in larger lattice distortion, further causing the formation of nano-domains in Ti-V-Al based alloys. Besides, no endothermic and exothermic peaks were detected due to the confinement of alpha-phase, and the emergence of nano-domains. With increasing H atoms content, the mechanical properties such as fracture strength, hardness, recoverable strain for Ti-V-Al based shape memory alloys initially increased and then decreased. (Ti-13V-3Al)99.2H0.8 shape memory alloys exhibited the highest fracture strength of 862 MPa, superior hardness of 307HV, and the fully recoverable strain under 6% pre-strain as well as the moderate elastic modulus, which was mainly attributed to the solution strengthening of interstitial H atoms and the precipitation strengthening of alpha phase. The best corrosion resistance of Ti-V-Al based shape memory alloys was observed with the 2.0 at. % H, which was due to the formation of TiO2, Ti2O3 oxide films. Moreover, the best wear resistance with the lower wear rate of 0.9347 x 10-6 mm3/N mm was obtained in (Ti-13V-3Al)99 & sdot;2H0.8 shape memory alloy, due to the integrated effects of higher micro- hardness, reinforcing effect of alpha phase and lubrication effect of the hydrogenated film.