Volume 2, Issue 8 (September 2005)
Effect of Aging Treatments on the Tensile Properties of Ti-35Nb-7Zr-5Ta-(0.06–0.7)O Alloys
Ti-35Nb-7Zr-5Ta rods containing 0.06, 0.46, and 0.68 wt.% oxygen were produced by vacuum arc melting and forging. These were solution treated (ST) and aged in the temperature range of 427–593°C for 8 h followed by air cooling. Increasing oxygen content increased the ST yield strength (YS) from 530 to 1081 MPa. The largest increase in YS, 630MPa, in ti-35Nb-7Zr-5Ta-0.06O observed after aging at 427°C was associated with ω phase precipitation. While the largest increases in YS, (1060 and 1288 MPa, in Ti-35Nb-7Zr-5Ta-0.46/0.68O) observed after aging at 482°C were associated with fine and somewhat inhomogeneous precipitation of the α phase, the tensile elongation remained above 8%. Aging at 538 or 593°C led to an increase in the inhomogeneity in α phase precipitation in Ti-35Nb-7Zr-5Ta-0.46/0.68O, precipitate free zones clearly being observed along with prior β grain boundaries, which served as preferred paths for early crack propagation and decreased tensile ductility.