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

Abstract

The effect of rolling temperature on both two- and single-phase regions and annealing in a temperature range of 700–950°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°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°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°C followed by annealing at 750°C and aging at 570°C.

Keywords

beta-rich two phase Ti alloy / thermomechanical processing / tensile properties / microstructure

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