| 6A02 aluminum alloy has been widely applied to Lightweight aeronautical structure materials for its good plasticity, excellent corrosion resistance and high specific strength. Hot processing is one of the most important way of plastic processing for this alloy and appropriate control of processing parameters is essential to obtain favorable microstructure and mechanical properties. This work studied the hot deformation behavior and corresponding microstructure evolution mechanism for 6A02 aluminum alloy in the temperature range of 410℃-450℃and strain rate range of 0.001s-1-1s-1. The correlation between flow characteristics, microstructure evolution and hot workability was systematically analyzed and microstructure mechanisms of different processing domains were illuminated. Therefore, the goal of processing parameter optimization and microstructure prediction and control was achieved. Based on the experimental research, the simulation of forging process for 6A02 aluminum alloy was conducted and optimum forging plan was proposed.Based on isothermal compression tests of 6A02 aluminum alloy, the hot deformation behavior of this alloy was investigated. A strain compensated Arrhenius constitutive model and a modified Johnson-Cook model were established and the prediction accuracy of both models was evaluated. It was found that Arrhenius constitutive model had better performance than modified Johnson-Cook model. Besides, critical strain model and dynamic model for dynamic recrystallization were constructed validated by microstructure observation.According to isothermal compression tests, the microstructure evolution of 6A02 aluminum alloy during hot deformation was investigated. Moreover, the processing maps of this alloy were built on the base of dynamic material model and Prasad instability criterion. It was found that dynamic recrystallization was the main softening mechanism for the alloy during hot deformation. At high temperatures and low strain rates, an obvious growth of recrystallized grains was observed. It was also discovered that processing domains with high power dissipation efficiency were generally characterized by fine grains. However, power dissipation efficiency was not the only criteria to evaluate hot workability for high power dissipation efficiency also appeared in instable domains where mircrocracks were observed. Considering every aspect, the optimum processing parameters for 6A02 aluminum alloy were determined to be 450℃-470℃/0.1s-1-1s-1and 430℃-450℃/0.01s-1-0.1s-1.Based on experimental research, the forging processing of 6A02 aluminum alloy was simulated. After a contrast between several mould plans, it was found that closed isothermal forging was the most appropriate. Effective stress of the blank during plastic flow is quite low so the requirement for forging equipment and mould strength is not stringent. Therefore, dimensional accuracy was the main concern for forging design. Fortunately, satisfactory filling of the blank can be achieved by closed forging and high dimensional accuracy can be guaranteed. According to the established dynamic model for dynamic recrystallization, the final forging was supposed to be characterized by full dynamic recrystallization. |
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