Effect of shoulder plunge depth on the weld morphology, macrograph and microstructure of copper FSW joints

In this study, the origins of materials comprising different zones of the joint in friction stir welded copper plates were investigated using a novel technique. In this method, after starting the welding, plunge depth of the shoulder was decreased from 0.3 mm to zero, gradually. This enables characterization of the material flow in the stir zone. The aim of presented investigation was to understand the formation of regions and flow of material in the welded joint that is produced by a non-threaded pin. Results of this study show that the weld joint is bonded by four different zones. In each rotation of the tool, all these zones are merged and one new layer of weld is produced.