Effect of hot rolling and annealing temperatures on the microstructure and mechanical properties of SP-700 alloy

The effect of rolling temperature on both two- and single-phase regions and annealing in a temperature range of 700-950 degrees C on the microstructure and mechanical properties of Ti-5Al-4V-2Fe-1Mo alloy was investigated. The results indicated that the best balance of strength and ductility is obtained by rolling in the two-phase region due to the globularization of the alpha phase and increase in its volume fraction. After rolling in the two-phase region, the ductility of the specimens annealed at 700 to 800 degrees C increased because of the finer size and globularized alpha phase, while the reduction in strength was attributed to a decrease in the alpha phase volume fraction. However, at 950 degrees C, the strength increased and ductility dropped by the formation of acicular alpha phase due to an increase in the phase boundary area. Annealing and aging after rolling in the beta-phase region increased the strength and decreased the ductility, which is attributed to the formation of a secondary alpha phase. A combination of favorable yield strength (1113 MPa) and elongation (13.3%) was obtained through rolling at 850 degrees C followed by annealing at 750 degrees C and aging at 570 degrees C.