Effect of Retrogression and Re-thermomechanical Treatment on Microstructure and Properties of 7075 Aluminum Alloy
摘要
In order to obtain excellent properties, the 7075 aluminum alloy was subjected to retrogression and re-thermomechanical (RRT) treatment. The properties of the alloy were investigated by hardness, friction and wear test, exfoliation corrosion, intergranular corrosion, and electrochemical corrosion test. The 3D morphologies, corrosion morphologies, and microstructure were observed by confocal laser scanning microscope, scanning electron microscopy, and transmission electron microscopy. The study revealed that the overall performance of the alloy had a substantial improvement following retrogression and re-thermomechanical treatment. The morphologies of matrix and grain boundary precipitates significantly changed as deformation increased. After RRT-3%, the comprehensive performances of the alloy were the best. The hardness of the alloy was 192.4 HV, the friction coefficient was 1.771, the wear amount was 13 mg, the exfoliation corrosion rating was P, the intergranular corrosion depth was 26.8 μm, the corrosion current density was 0.000632 mA/cm2, and the corrosion rate was 0.0207 mm/a. In addition, the matrix precipitates were fine, numerous, and uniformly dispersed throughout the matrix, which significantly improved the mechanical properties of the alloy. The grain boundary precipitates were independent, round, and clearly discontinuous distribution, which led to the difficult formation of anodic corrosion channels and significantly improved the corrosion resistance of the alloy.