Development of new titanium alloys with superior biocompatibility

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To develop new biocompatible titanium alloys in this research project, the binary alloy of titanium and zirconium, which is also known as a biocompatible metallic element, was investigated. The tensile strength of the binary alloy was 900-950 MPa when the contents of titanium and zirconium were higher than 30% each, while those of the two elements were 300-350 MPa. In addition, the strength increased with a third element, which suggests the possibility of a metallic biomaterial possessing even higher strength.In an immersion test, the amount of released ions from titanium-zirconium alloy was considerably lower than those from the pure component metals. Biocompatibility of the alloy was examined by a subcutaneous implantation test using rats. As a result, titanium-zirconium alloy was proved to be more biocompatible than titanium.Dental casting of Ti-6Al-7Nb alloy was also investigated with the aim of improving the biocompatibility and the castability of Ti-6Al-4V alloy. Although the tensile strength of Ti-6Al-7Nb casting was slightly lower than that of Ti-6Al-4V,the elongation of the former was about 7%, much larger than that of the latter. The mechanical property of Ti-6Al-7Nb was less scattered and was evaluated to be more reliable by better castability. Therefore, Ti-6Al-7Nb was proved to be practicable enough as a dental casting alloy.In addition, mechanical properties of TiAl-base alloys were examined. TiAl-base alloy is an intermetallic compound and a promising heat-resistant material. The strength of this alloy increased by the addition of niobium, and it is thought to be another candidate for a metallic biomaterial.