Research On Vertical And Transverse Property Of 7×50 Alloy Thick Plate

Al-Zn-Mg-Cu ultra-high strength alloy thick plate is now widely used in aerospace field as structural material. So far, the components of most plates in our country can be controlled well within the required range, but the performance of which is still poorer compared with that of foreign countries.When ultra-high strength aluminum alloy thick plate is used in the manufacture of aircraft, the performance of which in vertical, transverse and thickness direction are required to be as similar as possible. So the research on the performance in vertical, transverse and thickness direction of ultra-high strength aluminum alloy thick plate is of great importance.This experiment utilizes optical microscopy, scanning electron microscopy, energy disperse spectroscopy, XRD texture detection and mechanical testing and some other means to research the influence of reduction rate, heat treatment systems and Zr content on the performance in vertical, transverse and thickness direction of 7×50 alloy thick plate after heat treatment. The main results are as follows:(1) During the process of 7050 alloy ingot hot rolling to 30mm thick plate, the strength of the alloy first increased and then decreased with the increase of the reduction rate. The strength in vertical and transverse of the alloy both peak and are similar at the reduction rate of 70%, and the texture intensity of most recrystallization texture of the alloy are basically the same. When the reduction rate of the alloy is less than 70%, the strength in vertical is higher than that in transverse, while the strength in transverse is higher than that in vertical when the reduction rate of the alloy is more than 70%. With the reduction rate of 7150 alloy 60mm thick plate gradually decreasing from the surface to the center, the strength in vertical is first higher and then lower than the strength in transverse of the alloy after be heat treated.(2) As the extent of solution treatment is more and more fully, S phases in 7150 alloy 60mm thick plate gradually dissolve in the matrix, and the degree of recrystallization of the alloy increases. When the second-stage solution treatment remains 2.5h at 480℃, the difference between strength in vertical and transverse of plates different thickness layers is obvirous, strength in transverse is higher than that in vertical at the surface of the plate, while strength in vertical is higher than that in transverse at the center of the plate. Increase the second stage time for 5h at 480℃, the difference between strength in vertical and transverse of the alloy becomes smaller.(3) With the increase of Zr content, the size, quantity and distribution of the phases in the structure of 7150 alloy 12mm thick plate after heat treatement have no significant change, but the degree of recrystallization of the alloy is getting lower and lower, which indicates that Zr hinder the process of recrystallization of 7150 alloy 12mm thick significantly.(4) With the increase of Zr content, strength of 7150 alloy 12mm thick plate improves after heat treatment; 7150 alloy 12mm thick plate without Zr is almost isotropic; With the Zr content increasing to 0.093%, strength in transverse of the alloy is always higher than that in vertical; When Zr content is higher than 0.093%, strength in vertical is higher than that in transverse of the alloy; When Zr content is in the vicinity of 0.093%,7150 alloy 12mm thick plate has a low degree of anisotropy after heat treatment.