Defect formation and microstructural changes in friction stir welds between pure copper and a brass alloy

Abstract

Several attempts have been made in the last few years for joining similar pure copper and brass alloys using the solid state friction stir welding (FSW) process. For both material types, all the works performed reported that the production of defect free welds is largely dependent on the correct choice of process parameters. It was also observed that, despite grain refinement occurred in the centre of all the welds, the welds in copper showed a slight reduction in strength, when compared to that of the base material, as opposed to welds in brass alloys, for which an increase in strength was observed. Regardless of the encouraging results obtained in similar FWS of these materials, in the knowledge of the authors, few reports exist concerning dissimilar joints between them. In his work, dissimilar welds between Cu DHP cooper plates and Cu-Zn 37 brass plates, both of 1 mm thickness, with the brass plate positioned in the advancing side of the tool, were analysed. Welds were carried out with a solid tool made of high speed steel. Tool geometry was characterized by a tool shoulder of 10 mm in diameter, containing a conical cavity of 6 degrees, and a threaded probe of 3 mm in diameter. Welds were done in a milling machine, in position control, using the working parameters indicated in table 1.