Aging treatment and mechanical properties of Ti-29Nb-13Ta-4.6Zr alloy for biomaterial applications coated with bioactive calcium phosphate invert glass

In recent years, the opportunity of the hard tissues such as bones, hip joints and tooth to be replaced by metallic biomaterials is increasing. In general, metallic biomaterials lack bioactivity, which is the ability to directly form a chemical bond with bones. Therefore, the bioactive surface modifications on surface of metallic biomaterials have been investigated and applied. Among them, the calcium phosphate invert glass coating method, which is dip-coating treatment (DCT), can be granted the bioactivity on the surface of β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy, for biomaterial applications. In this study, aging characteristics and mechanical properties of TNTZ alloy surface-modified with DCT were investigated. There is an oxide layer and a case near boundary between calcium phosphate invert glass layer and TNTZ surface in TNTZ surface-modified with DCT (TNTZ _DCT). A very fine ω phase precipitates in an equiaxed β phase with an average diameter of 20 μm at a distance of 200 μm from specimen surface. On the other hand, the microstructure of aged TNTZ _DCT has an α phase. The tensile strength of TNTZ _DCT is around 30% greater than that of as-solutionized TNTZ (TNTZ _ST). On the other hand, the elongation is around 48% smaller than that of TNTZ _ST. Tensile strength of aged TNTZ _DCT is around 26% greater than that of TNTZ _DCT. While the elongation of aged TNTZ _DCT is around 52% smaller than that of TNTZ _DCT. Fatigue limit of TNTZ _DCT is nearly equal to that of TNTZ _ST. Fatigue limit of aged TNTZ _DCT is around 80 MPa greater than that of TNTZ _ST. Fatigue limits of TNTZ _DCT and aged TNTZ _DCT, where their fatigue specimen surfaces are mirror-polished, rise as compared with those of TNTZ _DCT and aged TNTZ _DCT, where their fagigue specimen surfaces are shot-blasted.