Dynamic recovery and recrystallization mechanisms during ultrasonic spot welding of Al-Cu-Mg alloy

The 2024-T3 Al alloy substrate and 2014-O Al alloy sheet have been well welded by ultrasonic spot welding (USW). Microstructure and texture of the original and welded samples have also been investigated via scanning electron microscope (SEM), Electron backscattered diffraction (EBSD) and transmission electron microscope (TEM). The results show that dynamic recovery (DRV) formed lamellar structure with shear texture of {111} (110) and Rotated Cube {001} (110) components in the sheet of the welded sample, while dynamic re crystallization (DRX) developed heterogeneous fine/ultrafine equiaxed grains with a sharp recrystallization texture {311} < 136 > component in the interface zone of the welded sample. Furthermore, we systematically explored the DRV and DRX mechanisms controlling microstructure and texture evolution during the USW process. We also observed and discussed the fragmentation and dissolution of the Al-Cu-Mg alloys precipitates during the USW process.