Effect of heat treatment and deformation on the microstructure and mechanical properties of SP-700 titanium alloy

This study investigates the effects of cold working prior to aging on the microstructure and mechanical properties of SP-700 titanium alloy. The results indicate that the microstructure of the quenched alloy comprises blocky primary α, retained β, and acicular a" martensite distributed in the β matrix. The retained β is transformed to denser and finer brittle acicular martensite α" by stress-induced martensitic transformation and the quantity of retained b decreases with higher degrees of cold working. The quenched alloy exhibits not only low yield strength, but the stress-induced martensite leads to a distinct increase in strength with good ductility. Plastic deformation prior to the aging treatment produces a great increase in the yield strength due to refinement of the precipitate microstructure, leading to the ratio of strength increment and ductility being very low.