| The magnesium alloy is one of the lightest common metal materials and easily recycled, having high specific strength, high specific rigidity, dimensional stability, excellent electromagnetic shielding properties, and thermal conductivity. The hexagonal crystal structure (HCP) of magnesium alloy leads to low forming ability, which causes some difficulties for AZ31magnesium alloy bulging. Based on the low forming ability and good electromagnetic shielding properties of magnesium alloy, this paper studies once bulging and secondary bulging experimental results, using self-made bulging molds, to seek out a new kind of optimized forming process for better bulging AZ31magnesium alloy sheets.The stepped mold and three-cavity mold were designed and processed to bulge AZ31magnesium alloy plates, and then determined the best bulging process. And analyzed the microstructure and cavity distribution of AZ31magnesium alloy parts to provide a theoretical basis for the AZ31magnesium alloy bulging.Firstly, once bulging and secondary bulging experiments were conducted by self-made stepped mold. AZ31magnesium alloy sheets with thickness0.7mm were used and pre-heated for15min in the experiment. Stepped pressurized method was used in the process of once bulging. It refers to the pressure is increased every10min by0.1Mpa from0.2MPa to1.3Mpa. The secondary bulging also used the stepped pressurized method. The difference is that the pressure was carried out in two times and the maximum pressurized value and pressurized time was changed in each stage. The pressure was added to1.OMpa within90min for the first time and the pressure was added to1.0Mpa within50min for the second time in the whole secondary bulging. The effects of once bulging and secondary bulging experiments were compared to deeply analyze the differences of two processes. The once bulging and secondary bulging microscopic mechanism and the cause of such a mechanism were studied by analysis of metallurgical microstructure. |
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