Deformation-free manufacturing Al alloy laminated structures by an ultrasonic-assisted diffusion bonding

The diffusion bonding with little to no distortion has always been a pursuit for precision production of metal laminated structures. Forming an interfacial metallurgical bond at a lower pressure using diffusion bonding is a difficulty. Herein, aluminum alloy laminated structures were successfully manufactured by an ultrasonic assisted diffusion bonding, which was carried out at temperatures below 400 °C and pressures of 3 MPa using a Zn interlayer. A manufacturing technique including solid phase diffusing, liquid phase ultrasonic vibrating and ultrasonic-assisted diffusing was developed. The surface oxide films of Al alloys in a laminated structure were separated from the base metal through the solid phase interdiffusion and suspending in the generated ZnAl eutectic liquid phase. A joint composed of alternating layers of Al/(ZnAl diffusion layer)/(oxide film)/(ZnAl diffusion layer)/(oxide film)/(ZnAl diffusion layer)/Al was formed between laminated sheets of aluminum alloy. The oxide films were then fractured using ultrasonic vibration. A bond between the two sheets was achieved by further ultrasonic-assisted diffusing, resulting in a composition mainly consisting of α-Al solid solution phases. The laminated structure exhibited a bending property similar to the 6063Al base metal, had a higher tensile strength (strength coefficient of 132%). Additionally, the breaking mechanism of multilayer oxide films by the cavitation effect of ultrasonic and the strengthening effect of geometrically necessary dislocations on the bonding interface during tensile testing were discussed in detail. The ability to simultaneously form multiple interfaces suggests an economical and practical method for manufacturing laminated structures.