Study on Weld Formation and Microstructure of TC4 Titanium Alloy Laser-TIG Hybrid Welding

Laser-tungsten inert gas (TIG)hybrid welding tests of TC4 titanium alloy were carried out, and the effects of different TIG currents on the joint surface morphology, weld formation and microstructure were studied.The results show that the continuous and complete TC4 titanium alloy welded joint can be formed under laser-TIG composite welding. With the increase of the current, the weld cross section gradually changes from "nail" shape to "funnel" shape, and the average porosity area decreases first and then increases, and it reaches the minimum value when the current is 50 A.Under the hybrid action of laser-TIG, the molten pool flow becomes more intense with the increase of current, and the grain size of the weld decreases first and then increases. The microstructure of the weld is mainly composed of mesh basket structure with acicular α'martensite and β band, α_gb phase and Widmannstatten structure.When the current is 50 A, the β phase band width between α'martensite bundles is wider, with an average width of 0.91μm.