Study Of Effect Of Multi-directional Forging Process On Microstructure And Properties Of Rare Earth Microalloyed 7085 Aluminum Alloy

Al-Zn-Mg-Cu alloy with high strength, high toughness, corrosion resistance and good processing properties is widely applied to the field of aviation and aerospace, such as the skin and structure of large aircraft. With the rapid development of science and technology, how to continue to improve the comprehensive performance of super-high strength aluminum alloy has become a new era of the new project. Rare earth microalloying and super plastic deformation are effective ways of strengthening and toughening at present. Minor addition of rare earth metals as modificator could obviously refine the grains of aluminum alloy and improve its properties. Alloy can possess finest grains and best comprehensive properties through SPD, and its average grain size is general in sub-micron and nanometer level. In this paper, the 7085 alloy was taken as the research object by adding minor of rare earth metal Sc and multi-directional forging process. Discussed the existence form and mechanism of Sc and the effect of multi-directional forging process on microstructure and properties on 7085 aluminum alloy. The research contents can be concluded as follows:(1) 7085 and 7085-1.5wt%Sc aluminum alloys were prepared using water chilling copper mould ingot metallurgy process. The homogenization processing (470℃/24h) of alloy ingot was conducted.(2) Designed on my own and manufacture multi-directional forging die. The experimental project and the process parameters of isothermal multi-directional forging were determined.(3) Single pass compression and multi-directional forging were performed on 7085-Sc aluminum alloy at a temperature of 400 ℃. The microstructure, mechanical properties and microstructure uniformity of the alloys were studied after two different deformation. The results show that compared to single pass compression, the grains can be obviously refined and the microstructure is uniform. The strength of 7085-Sc increased from 543.4MPa to 570.3MPa, and the elongation was 8.9% to 11.8%.(4) Effect of minor addition of rare earth metal Sc on microstructure and properties of 7085 aluminum alloy was studied in the paper. The results show that addition of rare earth metal Sc could strongly refine the grains and inhibit recrystallization. After multi-directional forging, the strength, hardness, plasticity of alloy were both significantly improved.(5) By changing the pass of multidirectional forging, studied the effect of different passes on the microstructure and properties of 7085-Sc aluminum alloy. It’s found that the tensile strength and elongation were up to 601.8MPa and 13.5%, respectively. Meanwhile, the grain size was refinement and the microstructure was uniform, so the degree of deformation strengthening was largest. With the increasing of passes, the holding time and accumulating strain were both increasing, as a result of that, the properties of 7085-Sc aluminum alloy through 9 passes.