Influence of in situ TiB reinforcements and role of heat treatment on mechanical properties and biocompatibility of Ti-alloys

The effect of heat treatment on the mechanical properties of Ti-35Nb-5.7Ta-7.2Zr (TNZT) and Ti-35Nb-5.7Ta-7.2Zr-0.5B (TNZTB) alloys has been investigated. In the case of TNZT alloy, the presence of omega phase in the matrix has a greater effect on strength and hardness than the presence of secondary alpha precipitates. The TNZTB alloy shows higher hardness and tensile strength than the TNZT alloy due to the formation of hard TiB precipitates in the matrix of the former. However, the boron free alloy offers higher ductility than the boron containing alloy. Presence of TiB precipitates in the matrix increases the strength of the TNZTB alloy when omega precipitates are present in the matrix. However, the boride precipitates have no substantial influence on the strength of the TNZTB alloy when omega phase in the matrix is replaced by the alpha phase. The elastic modulus of the TNZT samples shows a very small variation with different heat treatment conditions. The TNZT alloy samples containing beta and omega phases show higher elastic modulus than the samples containing beta and alpha phases. The elastic modulus of the TNZTB alloy is higher than that of the TNZT alloy due to the formation of high modulus TiB particles in the matrix. Both the alloys show better cell adhesion and spreading than the control material (polystyrene). However, the boron free Ti-alloy shows better cell attachment than the boron containing Ti-alloy.