Influence of High-Temperature Annealing on Microstructure and Properties of Welded Joints Using Narrow Gap Laser Welding of TC4 Titanium with Welding Wire

To solve the technical problems of poor strength–plasticity–toughness matching of titanium alloy welded joints, the optimized multi-stranded wires are used as the filler metal for narrow gap laser welding of TC4 titanium, and the welded joints obtained using high-temperature annealing were heat-treated at 850 °C holding 2 h. The macrostructure, microstructure and texture of both welded joints were compared by employing an optical microscope, scanning electron microscope and transmission electron microscope, and the tensile and impact properties were also evaluated. The results show that after heat treatment of the welded zone acicular α' martensite decomposition into lamellar α-phase + β-phase, the welded joint microhardness distribution tends to be smooth, the average tensile strength of the welded joints is 902 MPa, elongation is 14.5%, about 4.1% lower than the as-welded of the welded joints tensile strength, but elongation increased 3.5%, and room-temperature impact energy is 18.5 J, increased by about 54% than the as-welded impact energy, achieving a reasonable match of strength–plasticity–toughness of titanium alloy welded joints.