Effect of Beam Oscillation on Weld Formation, Porosity, Grain Structure, and Mechanical Properties in Electron Beam Welding 5B70 Aluminum Alloy

The 5B70 aluminum alloy holds broad application prospects in the aerospace industry, yet welding thick aluminum alloys encounters challenges such as porosity, weld formation issues, and coarse grain. In this study, 20 mm thick 5B70 aluminum alloy plates were joined using electron beam welding with oscillation and wire feeding techniques. The effect of oscillation amplitude on weld formation, porosity, grain structure, and mechanical properties of the joints was comprehensively investigated. From the cross-sectional morphologies of the joints, it is evident that porosity defects are distributed throughout the weld, which could be distinguished into metallurgical and process types, with characteristics influenced by hydrogen evolution and keyhole instability, respectively. Oscillation notably improved weld formation, practically eliminating the reinforcement height and porosity at an amplitude of 1 mm. Additionally, oscillation facilitated melt pool stirring, leading to a reduction in internal dislocation density and a refinement of grain size from 5.6 to 4.5 μm. This process significantly enhanced the mechanical performance of the joints, with ultimate tensile strength reaching up to 352.2 ± 25 MPa through the reduction of porosity and grain size, demonstrating the potential of combining oscillation and wire feeding techniques in electron beam welding of thick aluminum alloy for improved weld quality.