Numerical Prediction of Intermetallic Compounds Thickness in Friction Stir Welding of Dissimilar Aluminum/Magnesium Alloys

An atomic diffusion model is developed to predict the thickness of intermetallic compounds (IMCs) at the interface of aluminum/magnesium alloys in dissimilar friction stir welding. Both the temperature and the strain rate associated with dislocation density at the checking point are used to determine the diffusion coefficients. The variations of the diffusion coefficients and the thickness of IMCs are quantitatively analyzed at selected characteristic time instants during welding process. It is found that the dislocation density can increase the diffusion coefficient and plays a dominant role in the IMCs formation during the plastic deformation stage. Especially in magnesium alloy and Al12Mg17, the diffusion coefficient is increased by two orders of magnitude or even nearly three orders of magnitude by considering the dislocation density. The temperature is the main influencing factor after the end of plastic deformation. The model is validated by comparing the predicted thickness of IMCs with the experimentally measured results.