Effect of α2 Precipitation on Creep and Tensile Properties of Ga-Added Near-α Titanium Alloys

Abstract

The effect of α2precipitation on the creep and tensile properties was investigated for bimodal and lamellar microstructures in two Ga-added near-α Ti alloys with Al equivalences of 10.6 and 11.5. Fine α2phase formed in the α phase of both alloys. The volume fraction of the α2phase for the Al equivalences of 10.6 and 11.5 is equivalent to 57.6 % and 73.3 %, respectively, in the binary Ti-Al system at 600 °C. Creep tests were carried out under a constant stress of 310 MPa at 600 °C and tensile tests were performed at room temperature. Lamellar microstructure showed lower minimum creep strain rates than bimodal microstructure for both alloys. The increase in Al equivalence increased creep life by a factor of 1.6 and decreased the minimum creep strain rate from 6.51 × 10-8s-1to 3.99 × 10-8s-1in bimodal microstructure. In addition, the increase in Al equivalence decreased room temperature tensile elongation although both alloys contained a similar volume fraction of equiaxed α in a bimodal microstructure.