Effect of annealing treatment on microstructures and mechanical properties of TC4 titanium alloy manufactured by laser deposition

TC4 titanium alloy bulk specimens were prepared by laser deposition manufacturing. The effect of annealing treatment on mechanical properties, microstructure of LDMed TC4 titanium alloy was studied by optical microstructure (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The experimental results show that the microstructure is basketweave structure after alpha+beta two-phase region annealing treatment and is transformed to Widmanstatten structure after beta phase region annealing treatment. The mechanical properties still show significant anisotropy after annealing : Z-direction samples exhibit low strength and high plasticity, while XY-direction samples show high strength and low plasticity. The samples have a greatly decrease in strength and plasticity after beta phase region annealing treatment. The annealing temperature has obvious influence on the anisotropy of the samples. The tensile properties of XY-direction samples are evidently scattered. Both direction samples exhibit ductile fracture after alpha+beta two-phase region annealing treatment. The strength and plasticity of the samples decrease greatly after beta single phase region annealing treatment, and the XY-direction samples are brittle fracture.