Static Coarsening Behavior of Laser Powder Directed Energy Deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Titanium Alloy

The static coarsening behavior of laser powder directed energy deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy and its effects on the alloy's tensile properties were investigated. The static coarsening kinetics of the crab-like primary α (αP) and secondary α (αs) were satisfied by the Lifshitz–Slyozov–Wagner relationships. For the coarsening of the crab-like αP, the coarsening efficiency (n) was satisfied at 0.25–0.35 for 910 °C, whereas it was satisfied at 0.45–0.50 for 950 and 990 °C. For the coarsening of the αs, the n was satisfied at 0.45–0.50 for 950 °Cand 990 °C. Compared to the as-built sample, the samples heat-treated at 910 °C/2 h/air cooled and 950 °C/2 h/air cooled exhibited good yield strength (930–1005.5 MPa), the highest elongation (14.5 %–16.6 %), and the lowest anisotropic ductility (0.6 %) among all samples. The crab-like αP and αs increased the crack growth resistance and decreased the fracture difference in two different directions in the samples.