Texture evolution of refill friction stir spot welding in alclad 2A12-T42 aluminum alloy

Abstract

Electron backscatter diffraction (EBSD) was used to investigate the microstructure and texture evolution of 2A12-T42 aluminum alloy during refill friction stir spot welding (refill FSSW). The stir zone (SZ) and the thermo-mechanically affected zone (TMAZ) occurred dynamic recrystallization (DRX), with typical shear texture components. The texture is dominated by B component in the SZ, and dominated by A∗ and B components in the TMAZ. As the occurrence of the DRX, the storage energy of the grains gradually decreases, and there is a tendency to form lower energy grain orientations and texture weakening. The welding parameters determine the composition of the texture in different regions by influencing the degree of recrystallization. In the test group with the highest degree of crystallization, the SZ and TMAZ are dominated almost entirely by the B component. The TMAZ has more grains with soft orientation due to the difference in shear pattern and degree of recrystallization, which makes the texture reduce the mechanical properties of the joints. However, this reduction is not significant, with <10% variation for different test groups and regions. Compared to other strengthening mechanisms, the effect of texture strengthening is limited.