Phase Composition of Nickel Free Titanium Based Alloys withDifferent Composition and Heat Treatment

Ti-Mo and Ti-Nb alloys with different composition were melted by using vacuum arc furnace. The effects of aluminum, iron, tin, niobium and molybdenum elements on the phase composition of quenched and annealed alloys were studied. The results show that with increasing content of molybdenum, the α-phase content in annealed Ti-Mo alloy decreased, the β phase content increased, and α',α″ and β_M phases were formed sequentially in quenched Ti-Mo alloy. Aluminum and tin elements could increase the content of α phase in quenched Ti-12Mo and Ti-33Nb alloys, which acted as α stabilizer. In annealed Ti-12Mo and Ti-33Nb alloys, tin could suppress the transformation of β to ω, showing the tendency of β stabilizer. Aluminum increased α phase content in annealed Ti-12Mo alloy, but showed the tendency of β stabilizer in annealed Ti-33Nb alloy. Iron was a strong β stabilizer, which could increase the β or β_M phase in Ti-33Nb alloy and quenched Ti-12Mo alloy. However, due to the eutectic decomposition of β phase, α phase content in annealed Ti-12Mo-2Fe alloy increased. Niobium and molybdenum were also β stabilizers, which showed weaker effects than iron.