Nature of the interface between AA7072 alloy explosively clad to AA8090 aluminium alloy

Aluminium-lithium based alloy plates were explosively clad with Al-1 wt% Zn alloy sheets. Clad plates were evaluated for bond continuity, interface shape, microstructure, variation of elemental concentrations across the bond interface, and bond strength. Comparisons of selected characteristics were made with roll clad sheets developed earlier.Ultrasonic tests revealed the bond to be continuous at all locations except over 50 mm wide edges of the plates. Both straight and wavy shaped interfaces were observed, often alternating arbitrarily. Microstructures on each side of the interface were distinct and characteristic of the individual alloys bonded. No localized melting was observed in the interface regions. Elemental concentration varied sharply across the bond line in the as-clad condition, later changing to a smooth profile after heat treatment. The diffusion widths, when expressed as a percentage of the cladding thickness, were much smaller than the corresponding values of previously studied roll clad sheets.'Tensile shear strength' of the clad samples exceeded the shear strength of monolithic Al-1%Zn alloy, thus indicating good bonding. The bond strength values were marginally lower than those of roll clad sheets. These differences could, perhaps, be due to the differences in the extent of elemental diffusion across the bond interface between the two techniques.