Effect of pre-stretching on geometric accuracy and mechanical properties of 7075 aluminum alloy plates

The effect of pre-stretching on geometrical accuracy and mechanical properties of 6 mm thick 7075 aluminum alloy plate sheet was studied. The results show that the larger width to thickness ratio of the sheet, the smaller longitudinal permanent deformation after rebound when pre-stretching amount is the same. Pre-stretching has little effect on the width dimension of the plate, and its pre-stretching process is similar to the plane strain state of longitudinal extension and thickness reduction. Through data fitting, the relation equations between the pre-stretching amount and the permanent deformation rate after spring back in longitudinal direction and thickness direction for three kinds of heavy plate with width-to-thickness ratio are established. With the increase of longitudinal permanent deformation rate, the yield strength and tensile strength of the pre-stretched plate after aging show a trend of increasing first and then decreasing. When the longitudinal permanent deformation rate is 2%~2.5%, the strength performance of the pre-stretched plate reaches the maximum.