Microstructure formation of porous sintered Ti-Si-Zr compacts with mechanically alloyed-activated Ti-Si and TiH2 powders

Metallic implants are widely used in applications associated with bone. A major drawback of using metals is their elastic modulus which is higher than that of bone resulting in stress shielding and premature failure of the implant. The employment of biomaterials with a porous structure has the potential to lower the modulus and promote osseointegration. The present work investigates the microstructure formation and the resulting elastic modulus of a new Ti-Si-Zr alloy. The sintering procedure involves the use of both mechanically alloyed Ti-Si powder and TiH2 to activate sintering with the TiH2 also serving as a pore precursor. The procedure is designed to promote bonding but not consolidation. The influence of sintering temperature, heating rate, as well as the amount and size of the TiH2 on the phases formed and porosity was investigated. It was observed that the use of TiH2 increased the degree of porosity whilst the size of TiH2 particles could be used to control the pore size. The results showed that when using small TiH2 particles, the elastic modulus was strongly dependent on the fraction of TiH2. When large TiH2 particles were used, the porosity had no significant influence on the elastic modulus. The variation in behavior could be attributed to differences in microstructure. To control the bulk modulus it is essential to understand the differences in the microstructure formation mechanisms between these two cases.