| The thick plates of Al-Zn-Mg-Cu aluminum alloys with high strength are of indispensable structural materials in the industry of aerospace and armors. However, given the condition of relatively scant basic research on the theory and technology for processing the specifically thick-plate forgings of aluminum alloy, mostly causing the massive importation in high-performance thick plates of aluminum alloy, which restrains the technical development of aerospace and defense in our country definitely. Therefore, it is provident in the more accurate research on forging technology of aluminum alloy thick plates with high performance, which will facilitate our nation defense including aerospace industry and make sense totally.Concerning a new aluminum alloy of Al-Zn-Mg-Cu with high performance, this present thesis involves a scientifically research on the alloy's property of thermal deflection and multi-forging technology of thick plates. The procedures and results in the research are represented following:1.The flow stress behavior of hot compression in Al-Zn-Mg-Cu alloy was investigated with Gleeble-1500D Thermal simulator under a temperature range of 250℃~450℃and a rate of deformation from 0.001s-1 to 0.1s-1; the regular influence resulted from the change of flow stress conducted by temperature and stain rates was concluded and then help form the flow stress constitutive equations when thermal deflection occurred in this alloy; through the hot tensile test, alloy's tensile property was measured on the temperature from 250℃to 450℃and rate in 0.1s-1 of deformation. Hence, the material tensile strength, elongation and area reduction rate when worked from 250℃to 450℃founded the material thermal processing plasticity chart and ensured the forging temperature range in the real of 420℃~350℃.2.Microstructure revolution of hot compression in this alloy was deduced by means of thermal simulation and metallographic test. The conclusion indicates that the alloy of Al-Zn-Mg-Cu belongs to dynamic recovery metal, and that dynamic recovery is optimal in dynamic restoration mechanism. 3.The optimization of control parameters such as H0/D0, tool width ratio and reduction, as well as the simulation of multi-directional forging process containing upsetting and stretching were performed by Deform-3D. Multi-process multi-directional forging process of scale-down stock in two proposals embracing the first of threetimes-upstting with twice-stretching and the second of fourtimes-upstting with threetimes-stretching was simulated numerically. The results of simulation shows that: the total forging ratio is 17.86, equivalent strain in the forging reaches up to 12.6 in the first proposal; while the figure emerges at 13.34 and 9.23 respectively in the second one. The test results of experiment focused in scale-down stock in both technical proposals suggest that: tensile strength of forging surpasses 500 Mpa, elongations and reductions of cross section satisfy the application. Thus, the technical proposal of threetimes-upstting with twice-stretching not only enables the generation of Al-Zn-Mg-Cu alloy thick plate forging, but also simplifies the forging process and decreases the cost.4. The simulation of forging process of aluminum alloy thick plate within real sizes implicates that, during the generation of thick plate forgings by the forging technology of threetimes-upstting with twice-stretching when the total forging ratio designed in the scope of 13~15, forging effective strain within most regions stains to 9.96. Aluminum alloy thick plate within real sizes was successfully fabricated in Southwestern Aluminum Fabrication Plant, of which all the properties are available in application. |
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