Surface Modification Of Biomedical TiNiCu Alloy And Its Properties

In the present paper,the biomedical Ti_49.2Ni_50.8-xCu_x?x=5,7,10at.%?alloys were used as the research object and were subject to the thermal oxidation and nitrogen ion implantation in order to obtain both the good superelasticity and the improved surface performance.The effects of thermal oxidation temperature and nitrogen ion implantation dose on the microstructure,phase transformation behavior,mechanical properties,corrosion resistance,contact angle,hemolysis rate and antibacterial performance were systematically studied.The relationship between microstructure,surface modification parameters and properties of alloy was discussed,which provide theoretical guidance and experimental reference for its application in the field of biomedical sciences,especially orthodontics.The results showed that with the increase of thermal oxidation temperatures,the macroscopic surface color of TiNi7Cu alloy changed from the silver white of cold-rolled alloy to the golden yellow?400°C oxidation for 1h?,gemstone blue?450°C oxidation for 1h?and light blue?500°C oxidation for 1h?,and the size of the black precipitated phase firstly increased and then decreased,while the number of white precipitated phases gradually decreased until disappeared.The content of B19,TiO and TiO₂ phases gradually increased with increasing oxidation temperatures,and the new phases such as NiO and CuO appeared.A one-step B19?B2 phase transformation occurred during heating and cooling process of the thermal oxidized TiNiCu alloy,and its austenite transition end temperature?A_f?increased with the increase of thermal oxidation temperatures.After the thermal oxidation at 400°C/1h,the A_f temperature was about 23°C,while the A_f temperature was higher than 37°C after thermal oxidation at 450°C/1h and 500°C/1h.Compared with cold-rolled alloy,the hardness,wear resistance,corrosion resistance and antimicrobial resistance of the thermal oxidized TiNiCu alloy were all improved,while the surface contact angle and hemolysis rate were slightly decreased.During the nitrogen ion implantation process,with the increase of nitrogen ion implantation time,the surface roughness of TiNiCu alloy increased and the N/Ti atomic ratio gradually increased and tended to stabilize after 10 h.The content of Ti₂N and TiN phase in the alloy gradually increased with increasing implantation time,and Ti₂N was the main phase when the implantation time was less than 10h,while TiN was the main phase when the implantation time was more than 10h.In addition,the increase of copper content in the TiNiCu alloy matrix favored the formation of TiN phase.After nitrogen ion implantation,the TiNiCu alloy undergoes a one-step B19?B2 phase during the process of heating and cooling,and the A_f temperature was lower than 37°C.The hardness,wear resistance,corrosion resistance,mechanical properties and antibacterial properties of the TiNiCu alloy after nitrogen ion implantation were improved.In addition,the stability of superelasticity of thermo-mechanical treated TiNiCu alloy?cold-rolling and annealing,cold-rolling and aging?after nitrogen ion implantation for 10h in was also improved.