Study On The Aging Process And Hot Deformation Behavior Of 7N01 Aluminum Alloy

7N01 aluminum alloy is a type of Al-Zn-Mg series alloys which was developed by Japan.7N01 aluminum alloy has excellent performance, which has been widely used in the railway, aviation and aerospace fields. The effect of single-step aging treatment and two-step aging treatment on the hardness, tensile properties, conductivity of 7N01 aluminum alloy were investigated in this study. The microstructure evolution of 7N01 aluminum alloy at the aging process were analyzed by using optical microscopy (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM). The hot compression deformation behavior of 7N01 aluminum alloy was studied by the thermal simulation machine. The main conclusions in this study are shown as follows:(1) The special pattern structure can be discovered in the interior of grain, which is due to the segregation of Zn and Mg during the solidification. Many skeleton shape a-Al12(FeMn)3Si phases could be found at the grain boundary. The appropriate solution treatment is 470℃ for 2h, and the number of second phases significantly decreases during this treatment.(2) The best single-stage aging process of 7N01 aluminum alloy is 120℃ /24 h. At this condition, the hardness, tensile strength, yield strength, elongation and conductivity of the alloy is 104.6 Hv,331.4 MPa,161.7 MPa,16.7%, 32.5%IACS, respectively. The better two-step aging process of 7N01 aluminum alloy is 160℃ for 8h followed by 90℃ for 4h, the hardness, tensile strength, yield strength, elongation and conductivity of the alloy is 100 Hv,319.3 MPa, 155.6 MPa,9.3%,34.8%IACS, respectively. Compared with single-stage aging process, two-step aging can significantly increase the electrical conductivity of 7N01 aluminum alloy, which suggest that two-step aging process have good stress corrosion resistance.(3) Hot deformation behavior of 7N01 aluminum alloy was investigated by compression tests in the temperature range from 300℃ to 450℃ and strain rates from 0.01 s-1 to 1 s-1. The flow stress of 7N01 aluminum alloy is up to a peak value at a small strain, and the peak stress increases with the increasing of strain rate and the decreasing of deformation temperature. The average parameters of the hot deformation can be obtained by the linear retrogression method, and the result as follows:a=0.015, n=6.202,A=1.66×109 s-1, Q=133.799 kJ·mol-1(4) Recrystallization grains were not observed in the deformation alloy at the strain rate of 0.1 s-1 and 1 s-1, which indicate that the main softening mechanism was dynamic recovery. At the strain rate was 0.01 s-1, recrystallization grains were appeared in the alloy, which number and size increase with the increasing of deformation temperature. At this condition, the main softening mechanism was dynamic recrystallization, which was transformed by the dynamic recovery.(5) At different hot deformation condition, the micro-hardness of 7N01 aluminum alloy increase with the increasing of deformation temperature and strain rate. The conductivity of the 7N01 aluminum alloy increase with the increasing of strain rate during the deformation temperature was 300℃. The effect of strain rate on conductivity was not obvious during the deformation temperature was more than 300℃.