Organization Uniformization Extrusion And Microstructure Evolution Simulation Of Casting AZ31 Magnesium Alloy

At present, there is no discuss in forming magnesium alloy workpieces which own uniform grain size and outstanding mechanical behavior. With conventional feating method, the inner structure of the workpieces will become very complicate and inevitably influence the mechanical behavior of the workpieces. Because using conventional feating method will generate friction heat in the course of working, at the same time, the die and the workpieces will also eliminate heat to the external. This topic will form workpieces with outstanding mechanical behavior by controlling the temperature of the die and the deforming temperature of the workpieces. The key of solving the problem is the unit of computer simulation and frequent experiment, regular conclusions will be obtained from experiments. These problems will be solved:(1)A new rheological stress model be put forward. It is based on the influence of recrystallize-intenerate and workhardening to the stress-strain relationship. A new rheological stress model will be obtained which is more suitable to the conticasting AZ31 magnesium alloy. It is based on the curves of the compression experiment.(2)Simulate the development of the micro-organization under different deforming conditions. The material be pressecd in the reversed temperature field. The MSC.SuperForm be chosen to do the finite element simulation. The simulation uses the modified Yada model and the modified rheological stress model.(3)Design and machining the pressing die and the workpieces, determine the experimental scheme which is based on the simulative result. Do the pressing experiments and observe the metallurgical structures of the deformed samples. The results of the experiments indicate that the best pressing condition is the die's temperature 300℃and the samples'deforming temperature 250℃when the material be pressed in the reversed temperature field. Under theseforming conditions, the deformed samples will own uniform organization. And the sample has no dehiscence.(4)Give a conclusion to the development of the micro-organization under different deforming conditions when the material be pressed in the reversed temperature field. Variant micro-organizations equality be gained when the temperature spread between the die and the sample changed. If the samples own the same temperature, the missdistance between the die and the sample is more extented, the grain size in the brim of the cross-section is more similar with the grain size in the middle. If the temperature spread between the die and the sample have been fixed, the temperature of the sample is higher, the temperature of the die has more feebler influence to the grain size in the brim of the cross-section.