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 β-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 αˊˊ martensite to the coexistence of β parent phase and α phase, regardless of H content. Moreover, the amount of α 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 α-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 α 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 × 10−6 mm3/N mm was obtained in (Ti–13V–3Al)99·2H0.8 shape memory alloy, due to the integrated effects of higher microhardness, reinforcing effect of α phase and lubrication effect of the hydrogenated film.