Influence of plate position, tool offset and tool rotational speed on mechanical properties and microstructures of dissimilar Al/Cu friction stir welding joints

In this research, dissimilar friction stir welding between aluminium (Al) and copper (Cu) is investigated. The experimental results indicate that high quality joints can be obtained by placing the Cu plate on the advancing side of the tool rotation. Further improvement of mechanical properties and defect free joints could be obtained under specific critical offset towards the Al side. The maximum ultimate tensile strength of the weld was 95% of the Al base metal and bending angle was around 65 degrees. The Vickers micro-hardness distributions indicate that hardness values increased from Al to Cu side and maximum at the joint interfaces and hardness at the bottom of the nugget zone (NZ) was higher compare to middle and top layers. Broken grains were observed in the fractograph images at nano level. The XRD analysis of intermetallic compounds revealed that percentage of Cu and Al are almost same at the joint center and maximum at 2 mm away from the joint center towards Al and Cu sides, respectively. Line scanning indicated mixed flow of Al/Cu materials throughout the NZ. Microstructural analysis revealed the variation of the grain size in the weld zones and also with the process parameters. (C) 2016 Elsevier B.V. All rights reserved.