Influence of the magnesium content on cathode spot behavior in AC TIG welding of aluminum alloy

Abstract

The influence of magnesium contents on cathode spot (CS) behavior in aluminum AC TIG welding was investigated by High-Speed Video Camera (HSVC) observation with the maximum frame rate of 500,000 fps. The number of CS in A5052 case was larger than that in A1050, leading to the smaller average current per spot of 6.9 A comparing with 16.7 A in A1050. The larger current per spot is considered to cause the CS higher velocity. The average velocity of CS on liquid surface of A5052 was 110±37 m/s far lower than that in A1050 case. The central area, where the CS did not exist, had a radius of 2.0 mm and expanded over EP time. The existence of magnesium in A5052 led to the increase in the cathode spot number inside the weld pool. The predicted mechanism could be the more easy evaporation of magnesium than that of aluminum.