Microstructures performance and welding process of pulse TIG welded 7075 aluminum joints prepared with nano TiC aluminum matrix composite filler

The nanocomposite welding wire (Al-Zn-Mg-Cu) was used for AC pulse TIG (tungsten inert gas) welding of 7075-T651 superhard aluminum alloy. In response to the design value of tensile strength, the welding process parameters, such as welding pulse current, welding frequency and welding speed, were optimized by orthogonal test method. The tensile properties, welding pores and microstructures of welded joints with different process parameters were analyzed. The results showed that excessive welding pulse current and low welding speed can induce nanoparticles clustering and hydrogen bubbles nucleate at the particles grow up to pores. For tensile strength of welded joints, the optimum process parameters were welding base current 160 A, pulse current 180 A, welding frequency 100 Hz, welding speed 3 mm/s. The suitable process parameters favored the dispersion of nanoparticles and restrained the size of intracrystalline precipitation phases, which could improve the performance of welded joints.