Influence of Grain Boundary Quenching Precipitation Behavior on Intergranular Corrosion of 7099 Aluminum Alloy

The influences of grain boundary quenching precipitation behavior on the intergranular corrosion of 7099 aluminum alloy hot rolled thick plate were investigated by intergranular corrosion experiments, scanning electron microscopy and transmission electron microscopy. The results show that the intergranular corrosion grade and corrosion depth increase with the increase of the size and phase spacing of grain boundary precipitated phase, the PFZ width of grain boundary and the Zn and Mg contents of grain boundary precipitate phase. The size and PFZ width of grain boundary quenched precipitates increase from 24.8 nm and 21.5 nm to 136.4 nm and 121.6 nm, respectively. The contents of Zn and Mg increase from 5.3% and 3.6% to 21.6% and 17.4%, respectively. As a result, the intergranular corrosion level increases from 3 to 4, and the maximum and average corrosion depth increase from 96 μm and 65 μm to 247 μm and 186 μm, respectively.