The influence of heat treatment on the high temperature tensile properties of a near-α as-cast titanium alloy

In this study, a new high-temperature titanium alloy was designed and developed for use in the framework of hypersonic vehicle fuel tanks. The effects of heat treatment parameters on the microstructure and high-temperature tensile properties of the alloy were thoroughly investigated. At 700 ℃, the ultimate tensile strength (UTS) and yield strength (YS) of the alloy first increase with the increase of solution temperature, and then slightly decrease. Optimal strength and ductility are achieved after solution treatment at 1000 ℃ for 2 h, resulting in a UTS of 545 MPa, YS of 454 MPa, and elongation (EL) of 15.5 % at 700 ℃. The fracture behavior under the condition is characterized by a mixed brittle-ductile mode, predominantly featuring transgranular cleavage fracture. Aging treatments at different temperatures have minimal impact on UTS, YS, and EL, with microstructural analysis indicating only slight dimensional changes due to aging. The high-temperature deformation and failure mechanisms of the alloy were then discussed. It was found that nanoscale silicides enhance strength through precipitation strengthening, while microscale silicides reduce strength and accelerate fracture. The findings of this study offer valuable insights for improving the high-temperature tensile properties of titanium alloys.