Study on the inhomogeneity of Al-Zn-Cu-Mg aluminum alloy plates with different thickness

The microstructure and properties of a high Zn-containing Al-Zn-Cu-Mg (7065) aluminum alloy pre-stretched plates with 25 mm and 50 mm in thickness before and after two-stage aging treatment (121 degrees C/6 h + 151 degrees C/25 h) were investigated using optical microscopy, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy and properties testing machines. The results indicated that dynamic recrystallization was easy to occur near the surface, resulting in heterogeneous texture and dislocation density in the thick direction. After aging treatment, the precipitates at H/2 of the 50-mm plate were fine and dispersive because of the slow quenching rate and high dislocation density. The precipitation shearing mechanism was the primary precipitation strengthening pattern, and the tensile strength and elongation were similar to 550 MPa and similar to 15%, respectively. The electrical conductivity was increased by similar to 30% compared with the peak aging state with a slight reduction of hardness. The higher the precipitation degree and the lower the recrystallization degree, the higher the electrical conductivity. The abnormal anisotropy of mechanical properties in different directions was related to the number of Cube textures and the orientation of refractory particles.