Influence of cold plastic deformation after aging on the mechanical properties and microstructure of aluminum alloy EN AW-7075

Abstract

This paper presents research on the changes in the mechanical and structural properties of the commercial aluminum alloy EN-AW 7075 during thermomechanical processing. The processing involved artificial aging of the alloy at a temperature of 150°C for 30 minutes, followed by cold rolling after aging. Changes in hardness and impact toughness during the experiment were monitored. Hardness was measured using the Leeb method, while impact toughness was measured using the Charpy method. In the annealed state, the lowest hardness values were recorded, while the highest-impact toughness value was achieved in the as-quenched state. By applying cold plastic deformation after artificial aging, the hardness of the alloy significantly increased, while the impact toughness continuously decreased. After deformation of 20%, cracks appearance prevented further deformation. Optical microscopy was used to follow microstructural changes during the applied processing regime. Precipitates of various sizes and morphologies were observed in the structure. The annealed state results in poorly defined grain boundaries and formation of large precipitates relatively evenly distributed throughout the matrix. Cold plastic deformation after aging has resulted in elongated grain structure aligned with the rolling direction, along with crushing of secondary phase particles.