Investigation on the coupling interaction in electron beam welded Al–Cu bimetallic sheet

Two sound joints of Al–Cu bimetallic sheet with 6.5 mm in thickness were obtained in Cu (upper)–Al (lower) and Al (upper)–Cu (lower) welding configurations via the electron beam welding and their distinct coupling models were developed to well understand their flow behavior of the molten pool and microstructure evolution mechanisms during the electron beam welding. For the electron beam welding of the Cu–Al bimetallic sheet, liquid Al and Cu flowed into each other and fully combined in the fusion zone and the interface zone under high-temperature environment, forming large amount of intermetallic compounds. For the electron beam welding of the Al–Cu bimetallic sheet, liquid Al was floating on the Cu substrate, while liquid Cu was flowing at the bottom of the molten pool and mutually combined with liquid Al at the interface, forming a relatively small amount of intermetallic compounds. Moreover, a part of liquid Al flowed back to the seam root under the influence of the Marangoni effect. Therefore, the fusion zone and the interface zone with various phase compositions were formed in these two Al–Cu bimetallic joints and the mechanical properties of the corresponding joints were determined. Furthermore, the average tensile strengths of Cu–Al and Al–Cu bimetallic joints were 59 MPa and 67 MPa, respectively. The fracture locations of these two joints were both at the edge of the fusion zone along the Al2Cu intermetallic compound interlayer. Moreover, the fracture characteristics of these joints were mainly cleavage fracture.

Experimental study on bending behaviour of aluminium-copper clad sheets in V-bending process

The bimetallic sheets are used in the industrial sheet metal products to meet the demands of multi-functionality. The bending behaviour of bimetallic sheet is contributed by individual layers of the sheet and it is entirely different from the monolithic material. In this study, V-bending experiments are carried out to understand the springback, bend force and thickness change of Al-Cu clad sheets. The effect of different parameters such as sheet thickness, sheet setting condition, die angle, die opening and punch radius have been investigated. The results indicated that springback is more for smaller die angle, wider die opening and larger punch radius. Increase in die angle, increase in die opening or decrease in punch radius decreases the bend force. The clad sheet thickens at Al/Cu setting condition whereas it thins at Cu/Al setting condition. This thinning or thickening of the sheet influences the springback and bend force.