Enhanced diffusion and phase transformations during ultrasonic welding of zinc and aluminum

Elevated-temperature (513 K) ultrasonic welding of aluminum with zinc was investigated. The interface exhibits structures indicative of enhanced interdiffusion and local melting of Al-Zn solid solution. EDS analysis yielded an interdiffusivity value of 1.9 μm2/s. The enhanced diffusion and melting can be attributed to high strain rate (∼103 s−1) plastic deformation in aluminum, which may increase the instantaneous vacancy concentration as high as ∼10−1.