| Ultra high strength aluminum alloy has been widely used in aerospace and national defense fields because of its high specific strength, high toughness, low manufacturing cost and so on. In our country, the research of super high strength aluminum alloy started relatively late, in order to catch up with the foreign research, to meet the needs of Chinese aerospace defense. To explore the processing and heat treatment technology of ultra high strength aluminum alloy, especially the technology that can be applied in industry has been a subject of concern. Based on 7085 aluminum alloy as raw material, the effects of initial deformation energy storage, heating rate and solution time on Microstructure and properties of 7085 aluminum alloy have been studied.The specific tasks and achievements are as follows:(1) Based on 7085 Aluminum Alloy extruded materials, 40% thermal mechanical compression(350 ℃ × 2 h insulation) into 7085 Aluminum Alloy hot-pressed materials. Found that the hot-pressed materials in the hot-pressing process, the dynamic continuous recrystallization, resulting in a substantial decline in internal press alloy materials proportion of low angle grain boundaries, but still has a high dislocation, dislocation density is about 5.4 times of extruded materials, and the higher the deformation stored energy will speed up the hot pressing materials combined with the gold heat treatment process.(2) 7085 aluminum alloy during solid solution, the solute atoms dissolved into the matrix will produce atomic scale micro lattice distortion and substrate atoms, these micro distortion of lattice mobile, difference distortion annihilate each other, same number distortion are hoarding to form a large lattice distortion, with a large lattice distortion and by gradually converge in a row form the dislocation.(3) Because of the low initial deformation energy storage and the low temperature rise, the obvious recrystallization and grain growth will not occur in the process of heating up for the extruded materials. However, the hot-pressed materials with high initial deformation energy storage, slow heating could not effectively restrain recrystallization. On the contrary, the alloy occurred recrystallization and grain growth because of the long time in high temperature zon.(4) The mechanical properties of 7085 aluminum alloy were not significantly reduced by long time heating and solution. Slow heating and solid solution can inhibit the recrystallization of extruded materials with low deformation energy storage, but the temperature rising rate is too slow and the solution time too long is not good for the 7085 aluminum alloy extrusion. The hot-pressed materials due to have high initial deformation stored energy promote the recrystallization. In rapid heating and solution, hot-pressed materials occurred appropriate recrystallization which improved elongation but not reduced the strength. However, due to the low angle grain boundaries were consumed, the inter-granular corrosion resistance of the grain is decreased.(5) In the Y direction of hot pressing materials due to the hot pressing process lead grain is elongated and isometric descent. However, in the process of rapid heating and solution, Significant recrystallization occurred in the alloy which improve the grain isometric. It was found that the recrystallization could be controlled by adjusting the temperature rising and solution of the high initial deformation energy storage material, which could change the morphology of the grain and improve the corrosion resistance of the alloy.(6) The precipitation of the second phase was changed during the slow heating and solution treatment of 7085 aluminum alloy, which decreased the corrosion resistance of the alloy. The change maybe is coarsening, dissolved or precipitated new phase. In general the inter-granular corrosion resistance of hot-pressed materials was slightly worse than extruded materials in the same heat treatment.。... |
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