Heat treatment and mechanical properties of powder metallurgy processed Ti-35.5Nb-5.7Ta beta-titanium alloy

Beta titanium alloys are promising materials for bio-applications. For this purpose combination of high strength, low Young's modulus, good corrosion resistance and excellent biocompatibility is required. For dental implants new β-titanium alloy Ti-35.5Nb-5.7Ta was prepared via powder metallurgy process (CIP and sintering). The shape of wires required for dental implants was obtained by following thermo-mechanical processes - hot forging, heat treatment (850 °C/0.5 h/water quenched) and cold swaging. In order to control the resulting mechanical properties various final heat treatments (i.e. annealing at various temperatures and times) were performed on cold swaged specimens. The microstructure of cold swaged specimens consists of deformed elongated β-phase grains and fine α and ω precipitates. Recrystallization and precipitation processes take place during final heat treatment depending on annealing temperature. The microstructural changes correlate with changes in hardness. Recrystallization occurs and hardness decreases to about 200 HV10 in specimens annealed at 650 and 700 °C. On the other hand precipitation processes cause the increase in hardness to about 350 HV10 at specimens annealed at 500 °C.