Effect of heat treatment on microstructure and mechanical properties of laser melting deposited TC17 titanium alloy

Laser melting deposited (LMD) TC17 titanium alloy has a vast application prospect in aerospace industries. The mechanical properties of LMD TC17 as-deposited alloy exhibits excellent strength yet lower ductility. Therefore, in an attempt to improve the mechanical properties, anneal treatment for LMD TC17 alloy is firstly studied. The volume fraction of primary α phase (α_P) decreases and α lath coarsens with rising temperature, which is good for ductility but harmful for strength. Anneal treated LMD TC17 alloy cannot obtain optimistical combination of strength and ductility to conform to disk technical standard. The effect of solution-aging treatment on microstructure and mechanical properties of LMD TC17 alloy is further studied. The volume fraction of α_P increases and α lath coarsens with solution temperature rising, and α_S coarsens obviously when aged at high temperature. The mechanical properties are sensitive to volume fraction of α_P and α_S, as well as width of α lath. The ultra fine α_S precipitation in β matrix results in high strength. Coarsening α lath and increasing volume fraction of α_P are helpful for ductility. After 800°C/4 h, annealing and water quenching, then 630°C/8 h air cool treated, LMD TC17 alloy can obtain optimistical combination of strength and ductility, which conform to the disk technical standard.