Reasonable welding speeds are a prerequisite for obtaining high-quality joints by friction stir welding (FSW). In this paper, 2195-T8 Al-Li alloy FSW joints were successfully fabricated at different welding speeds (100–600 mm/min) with a constant rotation speed. The effect of welding speed on the microstructure and mechanical properties was analyzed under different experimental methods. Microstructural characterization was conducted using optical microscopy (OM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). Mechanical properties were measured by a hardness test and a tensile test. The results showed that the original T₁ precipitates disappeared in the nugget zone (NZ), generating many dislocations. With welding speeds increasing, joints obtained at lower welding speeds developed coarser T₁ precipitates in the heat-affected zone. Also, the equiaxed grains with a bigger size and a higher fraction of high angle boundaries (HABs) were detected in the NZ of these joints. As the welding speed increased, the area of hardness value changes gradually shrunk, which was consistent with the trend of the cross-section morphology. A kissing bond and macroscopic cracking were observed in the joints that were fabricated at the higher welding speeds. The appearance of those defects significantly reduced the ultimate tensile strength and elongation of the joints at high welding speeds. Fracture morphologies of the different joints were all characterized in quasi-cleavage fractures.

As a kind of typical high stacking fault energy materials, recrystallization behavior of high purity Al-0.5%Cu alloy is significantly influenced by the annealing process. In this study, different heating rate, target temperature, and holding time were discovered to have profound impact on the microstructures and textures of Al-0.5%Cu plates. Electron backscatter diffraction (EBSD), scanning electron microscope (SEM), and X-ray diffraction (XRD) were utilized for analyzing the evolution of the microstructure and texture in the subsequent microstructural characterization. Vickers hardness tests were employed for measuring hardness of specimens. The results showed that no obvious recrystallization was observed at lower temperature and the composition of texture influenced by rising temperature, heating rate affected initial recrystallization temperature, grain size, and strength of textures. After recrystallizing completely, the size of microstructures and the distribution of textures had little change with the extension of holding time.