Effects of retrogression and reaging heat treatment on the microstructure, exfoliation corrosion, electrical conductivity, and mechanical properties of AA7050

Abstract

The effects of different retrogression times and temperatures on the microstructure, electrical conductivity, exfoliation corrosion (EXCO), and hardness of the 7050 aluminium alloy were compared with the T6 and T7451 condition. The EXCO solution was prepared in accordance with ASTM G34-01 standard and the samples were kept in the solution for 48 hr. Corrosion depths were examined by using scanning electron microscope (SEM) in the cross-sections microstructure of the samples. The effect of EXCO on the material was investigated using stereo optical microscope images. In microstructure investigations, SEM and energy dispersive X-ray (EDX) analyses were used to determine the distribution and chemistry of the precipitates at the grain boundaries. The results show that retrogression and reaging (RRA) times and temperatures have significant effects on AA7050 EXCO. Especially after 200 degrees C/30 min RRA process, it has been found that 7050 aluminium alloy has higher mechanical strength than T6 level and high corrosion resistance from T7451 level. According to the results of this study, it has been shown that there is a direct connection between electrical conductivity and EXCO.