Al - Zinc - Mg - Cu Homogenization Heat Treatment Process Of Aluminum Alloy

In the current situation, the rapid advances in aerospace industry have demanded aluminum alloys with higher performance. In order to get good propertis, small percentage of the recrystallization is required in the final matrix. In present study, the microstructure, texture and property of high strength, high toughness and high hardenability7085aluminum alloy have been investigated during various homogenization heat-treatments. The main conclusions are as follows:(1) The formation mechanism of coarse second phase particles in as-cast samples of Al-Zn-Mg-Cu series aluminum alloy was revealed. The volume fraction of coarse eutectic-structure increases with the increasing of Zn content. Meanwhile, the accompanying precipitations of small Mg(Zn,Al,Cu)2particles have also gradually increased. When Cu amount is1.0%,1.4%,2.2%, the main second phases within grains are T (Al2Zn3Mg3) phase, S (Al2CuMg) phase, T (Al2Zn3Mg3)+θ(Al2Cu) phases, respectively.(2) The evolution of coarse second-phase particles of Al-Zn-Mg-Cu series aluminum alloy during homogenization heat treatment was explored. During homogenization, the dissolution of Mg(Zn, Al, Cu)2phase and transformation Al2CuMg occur at the same time. The transformed Al2CuMg particles and other second phases dissolve into the matrix gradually during homogenization at470℃.(3) The interaction between Al3Zr particles and the conventional second-phase particles was revealed, and the heat treatment technology prototype of homogeneous Al3Zr dispersoid particles was established. Al3Zr particles may heterogeneously nucleate on Al2CuMg particles in the grain boundary regions during homogenizing at400℃/12h+470℃/12h. So the precipitate free zone of Al3Zr particles becomes narrow. During the three-staged homogenization(450℃/12h+350℃/24h+480℃/12h), the dispersed MgZn2particles precipitate during the second-stage of homogenization may become heterogeneous nucleation nuclei of Al3Zr particles and promote the precipitation of Al3Zr particles in grain boundary areas. Mover over, the influence is more obvious compared with the two-stage homogenization.