Effect of Al₂O₃ film on weld appearance of stationary electron beam welded aluminum

Aluminum specimens with and without chemically cleaning were welded by electron beam to investigate the effect of Al₂O₃film on weld appearance.The removal mechanism of Al₂O₃ film during vacuum electron beam welding of aluminum was analyzed and the effect of Al₂O₃ film on molten pool flow behavior and weld appearance was investigated.The results showed that the weld width of the specimen was enlarged by chemically cleaning.The solid Al₂O₃film transformed into gaseous Al₂O via the reaction with liquid aluminum at the temperature higher than 1 350 K was the main reason for the removal of the film.The weld width was narrowed down by the oxide film due to the inhibition of outward flow driven by the surface tension gradient and the drag force between the Al₂O₃ film and liquid Al.The weld penetration was reduced in the initial stage and then enhanced in the metastable stage.