| Semi-continuous casting which relates to dynamic solidification process is the most popular casting way these days. It involves many nonlinear factors including geometry nonlinear and material nonlinear. It is liable to produce various casting defects, such as coarse grain, shrinkage cavity, shrinkage porosity, hot tearing, microstructure segregation and solute segregation. The effects of technological parameters and ultrasonic field on 7050 aluminum alloy ingot are studied by numerical simulation and experimental investigation, which mainly focused on microstructure and hot tearing sensitivity.1. The development and present status of 7xxx aluminum alloy semi-continuous casting are summarized. The microstructure numerical simulation of casting and some existing simulation methods are introduced. The simulation and criterions of hot tearing are also analyzed.2. The experiment of 7050 alloy ultrasonic semi-continuous casting is processed and the results are analyzed. The effects of ultrasonic field on microstructure, mechanic property and hot tearing formation are summarized.3. The microstructure of casting ingot is simulated by CAFE module which belongs to ProCAST. The mathematic model of CAFE is set up, meanwhile the correlative condition and parameters are chosen. The effects of different technological parameters on microstructure of 7050 aluminum alloy ingot are analyzed. The effect of ultrasonic on nucleation rate and undercooling is researched and the influences of different ultrasonic power on microstructure are also simulated.4. The hot tearing sensitivity in the casting process is simulated by HCS module which belongs to ProCAST, and the criterion of judging hot tearing formation-RDG criterion is chosen, which is analyzed based on the view of solidification and compensation. The effects of different technological parameters and ultra-sonic field on the hot tearing sensitivity of 7050 aluminum alloy ingot are also obtained. |
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