Modelling intermetallic phase formation in dissimilar metal ultrasonic welding of aluminium and magnesium alloys

Intermetallic compound (IMC) formation at the joint line usually has strongly detrimental effect on the performance of dissimilar metal welds. To understand the formation of IMC interlayers, and explore strategies to control their growth, a model has been developed and applied to the case of dissimilar joining of aluminium and magnesium alloys using ultrasonic welding. The model accounts for microbond formation during welding, diffusion across the joint line, as well as nucleation, spreading and thickening of the first IMC layer (Mg₁₇Al₁₂ phase) and the formation and simultaneous thickening of the second (Al₃Mg₂) layer. The model predictions match measurements reasonably well and the model has been used to predict the sensitivity of IMC layer thickness to weld temperature and time.