Microstructure and texture evolution of friction stir welded dissimilar aluminum alloys: AA2024 and AA6061

In this study, the development of the microstructure and crystallographic texture during friction stir welding (FSW) of AA2024 and AA6061 dissimilar joint was investigated. Electron backscattered diffraction (EBSD) technique was employed to characterize the textures and revealed the evolution of microstructures during friction stir welding. Experimental results showed the grain refinement in the stirred zone through continuous and discontinuous recrystallization. The fraction of precipitates in the stirred zone of the retreating side was much higher than that of the advancing side. On the other hand, the extent of continuous dynamic recrystallization in the thermomechanically affected zone (TMAZ) of the advancing side was lower than that of the retreating side and the recrystallized grains were rarely seen on the advancing side. The initial texture components of the sheets mainly consisted of {001}〈100〉 Cube and {011}〈011〉 Rotated Goss. The pole figures became asymmetric due to the inhomogeneous plastic deformation during FSW. The overall texture intensity was weaker on the advancing side and stronger on the retreating side than that in the starting materials. On the advancing side, {011}〈211〉 and {221}〈012〉 texture components created and the γ-fiber (〈111〉//ND) shear texture developed on the retreating side. Correlation between the microstructure and texture proved that the discontinuous static recrystallization and/or meta-dynamic recrystallization occurred on the advancing side. Microhardness profile on the advancing side was almost identical, while the profile revealed three distinguishable regions on the retreating side.