A titanium alloy contains vanadium, from 10 to 20% by weight; aluminum, from 0.2 to 10% by weight; and a balance essentially titanium, and the alloy has a microstructure including a martensite phase. Alternatively, the titanium alloy contains vanadium, from 10 to 20% by weight; aluminum, from 0.2 to 10% by weight; and a balance essentially titanium, and the alloy has a microstructure including a .beta. phase capable of transforming into a martensite phase by cold working or cooling under a room temperature.