Research on TIG welding organizational and performance of TC4 forge alloy

TC4 forged titanium plates with a thickness of 14 mm were multi-layer and multi-pass butt welded by non-melting tungsten inert gas welding (TIG), and the metallographic structure, crystal orientation and mechanical properties of the joints were investigated. The results show that the weld seams of TC4 titanium alloy welding joints are nicely formed, and the welding zone microstructure is mainly composed of columnar crystal and elongated acicular martensite α' phase. The microstructure of heat-affected zone is (α+β)+α′ phase, and base metal microstructure is (α+β) phase. Corresponding to the crystal orientation relationship, the grain interlacing distribution in the welding zone shows a certain preferred orientation according to different phases, among which the <111> and <001> direction is more preferred for the grain orientation at the bottom welding position, while the grain orientation distribution of base metal is not uniform. The tensile strength and elongation after fracture of the welding joint are 982 MPa and 6.0%, respectively, which are lower than those of the base metal, and all the bending tests produce cracks or fractures. The joint hardness first decreases and then increases from welding zone center to base metal, with the microhardness of the welding zone cover weld layer is slightly lower than that in the bottom weld layer.