•TIP-TIG was employed to achieve reliable welding of 20 mm thick TC4 alloy.•Mutually interlocked basket-weave microstructure is the key to joint strengthening.•Hot wire + swing process ensures the formation of the joint target microstructure. In this study, narrow-gap hot wire vibrating tungsten inert gas arc welding (TIP-TIG) technology was employed to achieve reliable welding of 20 mm thick TC4 alloy plates. Microstructure and mechanical properties of different regions within the welded joint were particularly investigated. The results show that the heat-affected zone (HAZ) exhibited a typical bimodal microstructure consisting of equiaxial α phase, αʹ phase, and β phase. Meanwhile, the weld center showed a basket-weave pattern of α phase and β phase. Microhardness gradually decreased from the base metal towards the weld center, with an average microhardness of 315 HV0.2 at the weld center. The welded joints exhibited an average tensile strength of 1043 MPa, and all samples underwent ductile fracture.