Characteristics of 2A02 Aluminum Alloy Overburned Structure and Optimization of Metallographic Examination Technology

In order to evaluate the overburned structure of aluminum alloy more accurately in metallographic examination process, taking 2A02 wrought aluminum alloy as an example, metallographic samples were prepared by superheating quenching. The traditional metallographic examination method was improved, and the characteristics and mechanical properties of overburned structure were analyzed. The results show that the volume ratio of 0.5% hydrofluoric acid etching is helpful to accurately determine the critical overburned structure under optical microscope. Scanning electron microscope and energy spectrum analysis can help operators to distinguish the characteristics and phase of critical overburned structure accurately. The microstructure of 2A02 aluminum alloy is normal when the solid solution temperature is below 510 ℃, and the hardness increases slightly with the increase of solid solution temperature. When the solid solution temperature is above 510 ℃, the primary melting ball gradually appears with slight overburned phenomenon. The intermittent network remelting grain boundary appears at 520 ℃, which is typical overburned structure. The grain boundary remelts and coarsens, and large-size remelting ball appears at 530 ℃, which is serious overburned structure. The local remelting ball becomes cavity at 550 ℃. The hardness and corrosion resistance of aluminum alloy decrease sharply after being overburned.