Joint Strengthening Mechanism in Electron Beam Welding of Al/Cu Bilayer Laminated Composite Using Double-Sided Method

The double-sided electron beam welding (EBW) was proposed to overcome the severe deterioration of mechanical properties and electrical conductivity of Al/Cu bilayer laminated composite in the single-sided EBW process. The results show that the sound butt joint was obtained via the double-sided EBW. For the double-sided EBW joint, the microstructures in the Cu and Al side welds were similar. In the weld edge, it consisted of well-developed columnar structures. In the weld center, the fine equiaxed structures formed. The results of scanning electron microscopy with energy-dispersive spectroscopy, electron backscatter diffraction and x-ray diffraction indicated that the interface zone consisted of Al2Cu IMC and (Al2Cu+α-Al) eutectic structure. Moreover, the tensile strength of the double-sided EBW joint was 116.9 ± 5.3 MPa, and the fracture position was at the center of the joint, which was approximately 93% of the base material strength and far superior to the performance of single-sided joints with Modes I (57.5 ± 3.7 MPa) and II (66.7 ± 4.6 MPa). Furthermore, the electrical conductivity of the double-sided EBW joint was 56.8 ± 0.4 MS/m, which could reach 99.3% of the base material conductivity and was significantly higher than that of single-sided joints with Modes I (38.5 ± 2.1 MS/m) and II (44.3 ± 1.7 MS/m), ensuring the functionality of the joint after double-sided EBW.