Material flow modeling for the DSFSW of magnesium alloy

Abstract

The Coupled Eulerian Lagrangian (CEL) method is utilized to model the double shoulder friction stir welding (DSFSW) of AZ91 magnesium alloy and then the model is verified by the experiments. The effects of tool rotational speed and sheet thickness on temperature and strain distributions as well as the material flow patterns are considered at different steps of the process. The material flow pattern around the tool pin is demonstrated properly and the shoulder driven and pin driven zones are predicted very well. Results show that, the material movement in shoulder driven and pin driven zones is different, while it is from the advancing side (AS) to the retreating side (RS) in the pin driven zone, it is inverse in the shoulder driven zone. Additionally, increase in rotational speed raises the maximum temperature and strain, improves the material movement, expands the SZ width and increases the depth of shoulder driven zone. Furthermore, increase in sheet thickness results in a decrease in maximum temperature and strain as well as the material movement. In the sheets with low thickness due to the effects of two shoulders, the pin driven zone is not distinguishable, however in thicker welding sheets the pin driven zone is obvious by significantly lower strains.