Studies On The Design And Properties Of Beta-titanium Alloys As Biomaterials

Based on the analyses of the recent evolution in the bio-titanium alloys researches and of the existent problems, and using the theories about titanium alloys design, the studies design three beta-titanium alloys: Ti-38Nb-6Zr, Ti-38.8Nb-7.7Zr, Ti-39Nb-3.7Zr. The alloys do not contain venomous elements and have lower elastic modulus. Test the mechanical properties and analyze the microstructures. After contrasting with each other, the best one to be studied was found out. The relationship between mechanical properties and microstructures of this kind Ti alloys in different treatments was analyzed in this paper. Research the relations between the mechanical properties and the treatments. In addition, the author analyzes the difference of the three alloys' surface structures after activate treatment. Observation of the microstructures of the coating at different treatment stages was carried out using TEM. The results show:1. According to the design precepts of bio-titanium alloys, Ti-38Nb-6Zr, Ti-38.8Nb-7.7Zr, and Ti-39Nb-3.7Zr alloys were worked out. Because of the high Mo eq values the β phase can exist at room temperature and doesn't turn to a phase.2. After tested the mechanical properties of the three alloys, Ti-39Nb-3.7Zr alloy shows out the best results. So we choose the alloy as the preferred one for later experiments.3. The coefficient of expansion of Ti-39Nb-3.7Zr is 9.075 X 10^-6K^-1. It is close to the one of K₂Ti_nO_2n+1. This is propitious to the bond between the alloy base and the coating. The casting Ti-39Nb-3.7Zr has high compressive strength and low Yang's modulus in the compressed state. But both the strength and the modulus go down after forging. Then the alloy was treated at different temperatures. The results show that the alloy treated at 850℃ has lower Yang's modulus and higher compressive strength. Contrast with Ti6A14V, Ti-39Nb-3.7Zr has better properties.4. In the activate treatment, Ti-39Nb-3.7Zr has better effects than others. By TEM analysis, at the first stage, acid treatment, a layer of rutile TiO₂ with nanostructure is formedon the surface. Then at the second stage, alkali treatment, it turns to be a layer of K6T12O7 with fine grain.The designed Ti-39Nb-3.7Zr alloy has fine biomechanics. After activate treatment the surface activity is improved, and the alloy has excellent biocompatibility.