Effects of hot deformation on microstructure evolution, hardness, and intergranular corrosion of 7085 aluminum alloy sheets

In this work, slabs of 7085 aluminum alloy were fabricated by electromagnetic stirring and solidifying with copper mold and suffered hot plastic deformation. The straight hot rolling process was used when the slabs were preheated to 420 degrees C for 1 h. The thicknesses of 1-, 2-, and 3-mm sheets correspond to the thickness reduction rate of 92, 83, and 75 % of original rectangular slabs. The microstructure results show that hot rolling deformation crushes the remanent phases into small sizes, leads particles into homogeneous distribution, and changes the dendritic grain into a fiber structure. The recrystallization rate decreases with the final sheet thickness increase after heat treatment. The recrystallization is strictly restricted when the thickness reduction rate approaches 92 %. EBSD results provide a unique perspective to view grain and dislocation evolution and texture change in different tempers of sheets. The hardness and intergranular corrosion (IGC) performance show that hardness is reduced while the corrosion depth is aggravated by the rise of sheet thickness. The maximum hardness is 86.75 HRB, and theminimum corrosion depth is only 9.17 mu m in the 1-mm sheet. The effects of grain boundary precipitates (GBPs), recrystallization, and precipitate-free zone (PFZ) on hardness and IGC were studied.