Evolution of Primary α Phase Morphology and Mechanical Properties of a Novel High-Strength Titanium Alloy during Heat Treatment

Abstract The evolution of primary α phase morphology and mechanical properties of a novel high-strength titanium alloy during heat treatment were investigated. The results show that the primary α phases exhibit a globular growth feature on the basis of the equiaxed α phases under double solution treatment at air cooling process of α/β zone. But abnormal growth of primary α grains occurs in the 0.5 °C/min furnace cooling process except that some primary α remains spherical growth, i.e. the other part of α grains evolve into similar “fork” shaped dendritic growth rather than keeping nearly spherical growth trend. The novel titanium alloy has attractive combinations of strength and ductility (≈1300MPa of ultimate strength with 10.5% of elongation) owing to the microstructures of equiaxed or thin billet-like primary α phase and fine needle-like secondary α phase after α/β solution treatment followed by air cooling plus aging. After α/β solution treatment followed by furnace cooling to low temperature and then aging heat treatment, the new type alloy has an excellent fracture toughness (≥80 MPa·m 1/2 ), and the elongation and reduction of area remain at about 19% and 45%, respectively, and its corresponding tensile strength is maintained at about 1000 MPa. It can be assumed that the alloy may be a usable structural material.