Modeling the dissimilar material flow and mixing in friction stir welding of aluminum to magnesium alloys

To study the dissimilar materials mixing and understand the underlying mechanism, a model for friction stir welding of aluminum to magnesium alloys is developed. The mixing dissimilar materials in the stirred zone are treated by a method similar to the functionally graded material, the physical parameters are exponentially related to the real volume fraction, and the influence of volume fraction index on the material distribution is analyzed. Furthermore, a modified method that uses a variable volume fraction index with radial distance away from the pin axis is proposed and employed. Compared with the constant volume fraction index equal to 1, the modified method can better predict the material mixing and distribution in aluminum-magnesium dissimilar joints, which lays solid foundation for analyzing the formation of intermetallic compounds in dissimilar friction stir welding of aluminum to magnesium alloys. •A model is developed to analyze the dissimilar materials flow and mixing in friction stir welding of Al and Mg alloys.•The volume fraction index is used to determine the physical properties of banded dissimilar materials in mixing zone.•A modified method with variable volume fraction index changing with position is established and applied to the model.•The calculated mixing zone based on the variable volume fraction index agrees better with the measured one.