Microstructure evolution and mechanical properties of dissimilar friction stir welded joints between AA1100-B4C MMC and AA6063 alloy

The feasibility of dissimilar friction stir welding (FSW) between the AA1100-16 vol.% B4C metal matrix composite and the AA6063 alloy has been evaluated. The effect of the welding parameters on the interface bonding, joint microstructure and mechanical properties was investigated. The results revealed that all dissimilar joints produced under welding conditions investigated were stronger than the base materials of the Al-B4C composite. Analysis of the Mg concentration and the B4C particle distribution indicates that good material mixing and seamless bonding was achieved around the interface between the Al-B4C composite and the Al 6063 alloy during FSW. The electron backscatter diffraction analysis (EBSD) shows that during dissimilar FSW, there was a gradual microstructural evolution on both material sides, resulting in a variety of grain structures in the different weld zones. In the weld zones of FSW joints, the materials underwent dynamic recovery and recrystallization to different extents depending on their thermal mechanical history. The grain refinement of both materials in the nugget zone was observed. It is recommended that the 6063 aluminum alloy should be fixed on the advancing side and the use of an appropriate offset to the 6063 aluminum side is preferred.