Effect of annealing treatment on the phase transformation and mechanical properties of TA15 alloy fabricated by WAAM

Wire arc additive manufacturing (WAAM) is a promising additive manufacturing technique with growing acceptance in aerospace applications. In this study, the effects of annealing treatment on the microstructure, texture and tensile properties of Ti-6.5Al-2Zr-1Mo-1V alloy fabricated by WAAM were investigated. The results indicated that the microstructure of the as-built specimens is composed of fine basketweave structure within the columnar prior-β grains. With the increase of annealing temperature, the microstructure of the specimen was transformed from fine basketweave structure to lamellar structure and then to bi-lamellar structure. Compared with the as-built specimen (0.48 μm), the average primary α phase thickness of the specimens annealed at 900 °C, 940 °C and 980 °C increased by 0.67 μm, 0.88 μm and 2.66 μm, respectively. Secondary α phases with width of 200 nm were also precipitated for the annealed specimen at 980 °C. In addition, compared with the as-built specimen (1014.8 ± 28.4 MPa, 5.87 %), the tensile strength of the annealed specimens at 900 °C (970.3 ± 9.5 MPa), 940 °C (929.1 ± 4.9 MPa) and 980 °C (922.4 ± 2.1 MPa) decreased slightly. The elongation of the specimens annealed at 900 °C, 940 °C and 980 °C increased by 63.5 %, 82.3 % and 125.4 %, respectively.