Effect Of Rolling Deformation On Microstructure And Properties Of Thick Plates Of Al-6.4Zn-2.3Mg-2.1Cu Alloy

Al-Zn-Mg-Cu alloy as a high-strength aluminum alloy is widely used in aerospace field and the alloy pre-stretching thick plate as high-strength lightweight structural material is urgently needed in aircraft manufacturing. So far, most of the researchers in the world have comprehensively researched the heat treatment, but there is little research on the microstructure and properties of this alloy thick plate, especially for the laws of microstructure and properties in deformation, so it still needs quite a lot of content make further in-depth research.This experiment utilizes optical microscopy (OM), scanning electron microscopy (SEM), energy spectrum analysis, transmission electron microscopy (TEM), mechanical testing and other means, by designing of rolling passes and total deformation, the rules of hot rolling state microstructure and T77state microstructure and properties of Al-6.4Zn-2.3Mg-2.1Cu30mm and80mm thick plate are researched. The main results acquired are as follows:(1) when rolling deformation is tiny, the near surface deformation of Al-6.4Zn-2.3Mg-2.1Cu alloy thick plate is greater than the deformation of the central portion, while the rolling deformation is more than70%, it does not change significantly; after the solution treatment, the level of recrystallization of low-pass rolling is greater than the multi-pass rolling one.After homogenization, the grains are nearly equiaxed shape; increasing the rolling deformation, cast structure and crystalline phases are easily broken; with the increase of the rolling deformation, after T77treatment the level of crystallization increases.(2) T7730mm thick plate of the alloy with the increase of deformation, the elongation is increasing gradually, the strength increases with the increase of deformation, when the deformation is more than70%, the strength decreases slightly with the increase of deformation; when the total amount of deformation is in the range of60%to70%, the center portion strength of the plate is greater than the surface strength, and vertical strength is higher than horizontal strength; when the total deformation is about80%, center strength of the plate is lower than surface strength and vertical strength is lower than horizontal strength; after the T7751treatment of79.5%rolling deformation of the80mm thick plate, the vertical strength from the surface to the center portion decreases gradually, the horizontal strength increases gradually from the surface to the center portion but the elongation decreases orderly.(3) There are three kind of textures in80mm thick plate,{112}<111>,{011}<211> and {123}<634> texture, these textures mainly occurred near the center of the thick plate; and the {112}<111> texture has the strongest intensity, the{011}<211> texture followed, the last is the{123}<634> texture, intensity of the{112}<111> texture is2times of the{011}<211> texture; after solution treatment, the{123}<634> texture intensity is almost unchanged, however the intensity of the{112}<111> texture and the{011}<211> texture are not only significant reduced, but also changed to half intensity of the hot-rolled plate texture and the strongest intensity position transforms to the3/4place of the thick plate surface; under the same circumstances, when the total deformation is same, increasing the deformation passes has not obviously effect on the type and intensity of the texture of the T7751state80mm thick plate.