The present work is focused on developing Ti-xTa porous alloys processed by the space holder method and solid-state sintering. The volume fraction of Ta ranged between 20 and 30 wt.%. The sintering kinetics was evaluated by dilatometry tests. Sintered materials were characterized by SEM, XRD and computed tomography. Porosity features and permeability were determined from 3D images, and their mechanical properties were evaluated from microhardness and compression tests. The sintering behavior and the final microstructure are driven by the Ta diffusion into the Ti, slowing down the densification and modifying the transition temperature of α-to-β. Due to β-stabilization, martensite α′ was obtained after sintering. Mechanical properties are reduced because of the β-stabilization and pore addition, being predominantly the pore effect. Permeability depended on the pore characteristics, finding values close to the human bones. It was concluded that powder metallurgy generates highly TixTa alloys with a combination of α, β and α′ Ti phases as well as remaining Ta particles that are beneficial to improve the biocompatibility and osseointegration of such materials. Being the Ti25Ta40salt alloy the most suitable for orthopedic implants because of its characteristics and properties.
This works proposes a methodology for fabricating materials with specific characteristics mimicking human bones. A Ti64 alloy powder was used as the base material and it was mixed with Ag, Ta, TiN and salt particles to obtain different features. A hip-bone like component was fabricated, including a highly porous core of Ti64/25Ta/5Ag and a compact outer shell of Ti64/5Ag that is supposed to improve corrosion and osseointegration. Besides, a harder cover surface in Ti64/10TiN composite should increase the wear resistance. The green component was sintered at 1260°C in argon. Its Young's modulus was close to the one of bones due to the added porosity, which also provided a permeability close to the one reported for trabecular bones. Tribocorrosion behaviour in simulated body fluid was improved by TiN addition. In conclusion, the proposed processing route was able to produce complex components fulfilling specific features required for human bone replacement.
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