Effect Of Homogenizing Annealing On The Microstructures And Mechanical Properties In 7005 Aluminum Alloy

7005 aluminum alloys are the Al-Zn-Mg series aluminum alloy that can be strengthened by heat treatment, which have good thermal deformation properties, wide quenching temperature range. Using appropriate heat treatment process, the alloys can reach a higher strength. They also have good weldability in high-strength aluminum alloy, but they have a certain degree of stress corrosion tendency. Homogenizing annealing can remove or change the coarse second-phase in aluminum alloy, improve the alloy's cold/heat distortion properties effectively, reduces the risk of cracking of hot-rolled. In this paper, the effect of homogenizing annealing on the microstructures and mechanical properties in 7005 aluminum alloy and homogenizing annealing process are investigated. The conclusions of the study are as follows:Homogenizing annealing can eliminate second-phase and dendrite in as-cast alloy effectively, reduce the volume fraction of second-phase greatly, and make alloy more homogenization. After homogenization annealing at 460℃for 24h, second-phase and dendrite in alloy are not be eliminated completely, there is still a large number of second-phase staying in the alloy. After homogenization annealing at 470℃for 24h, second-phase and dendrite are be eliminated completely. After homogenization annealing at 480℃for 24h, there is a large number of over burning structure in alloy. Therefore, the temperature of 7005 aluminum alloy homogenizing annealing process should be lower than 480℃.Homogenizing annealing can improve the distribution of main alloying elements by grain boundary diffusion and make the main alloying elements more homogenization. The main alloying elements Zn and Mg of 7005 aluminum alloy easily segregate with the second-phase form and the second phases gather together in the grain boundary, resulting in the imbalance distribution of Zn and Mg. Zn and Mg contents in the grain boundary are much higher than that in the matrix. After homogenizing annealing, the main alloying elements distribute more homogenization because of the second-phase's dissolution, so the spread of the main alloying elements tend to homogenization.Homogenization annealing improves the mechanical properties of the alloy effectively, especially to the plasticity. 7005 aluminum alloy refined by GRAI has better grain structure than that refined by Al-10Ti,and the structure was inherited at the process of homogenizing annealing ,and the alloy has a better plasticity after 460℃×24h homogenizing annealing; the alloy refined by Ti, Sc, Zr has the best cast structure and after homogenization annealing of the mechanical properties of alloy changes little. The addition of Ti greatly enhanced plasticity and the strength can be greatly improved by adding Sc, the alloy has the best strength refined by Ti, Sc, Zr and the best plasticity refined by GRAI.