Effect of annealing process on microstructure and properties of TC4 titanium alloy in arc additive manufacturing

Using a 1.2 mm diameter TC4 titanium alloy welding wire and an arc-based additive manufacturing system, thick-walled TC4 titanium alloy components were fabricated on forged TC4 titanium alloy base plates via a reciprocating scanning method. These components were subsequently annealed. The effects of annealing temperature and time on the microstructure, microhardness, and tensile properties of specimens with different sampling orientations were investigated using optical microscopy, scanning electron microscopy, and X-ray diffraction (XRD) to investigate the effects of annealing temperature and time on the microstructure, microhardness, and tensile properties of specimens with different sampling orientations. Results indicate that the aspect ratio of α phase in the microstructure decreases with increasing annealing temperature. Significant differences exist in the mechanical properties of the arc-based TC4 Ti alloy along the deposition direction and welding direction. Tensile strength in the deposition direction was markedly lower than in the weld direction, while elongation and reduction of area were higher in the deposition direction.Tensile tests in both directions revealed that α lamellae deformed or fractured primarily through two mechanisms: fracture in the deposition direction exhibited ductile fracture characteristics, whereas fracture in the weld direction displayed semi-cleavage and semi-ductile characteristics.