Influence of tool tilt angle on heat transfer and material flow in friction stir welding

摘要

The tool tilt angle is an important factor determining the microstructure and properties of friction stir weld joints. In this study, both experiments and numerical simulations are made to investigate the influence of tool tilt angle on heat generation, temperature field and material flow behavior in friction stir welding (FSW). The tool tilt angle induced non-contact area between tool shoulder and workpiece is determined under different sets of process parameters, and numerical simulations are conducted. It is found that the crescent-shaped uncontacted area gets larger when either the tool rotation rate or the welding speed increases. Compared with the case of 0 degrees tool tilt angle, a tilted tool produces stronger forging effect at trailing side, a larger region of high temperature at the trailing advancing side, a higher peak temperature and more intensified material flow around the tool. With consideration of tool tilt angle and pin thread in the new model, the predicted peak temperature at tool/workpiece interface and the thermo-mechanically affected zone match well with the measured ones.