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为研究压铸镁合金熔焊过程气孔的形成机制,对厚度为6mm的AZ91D压铸镁合金进行激光局部重熔。采用光学显微镜(OM)和扫描电子显微镜(SEM)观察母材组织和气孔形貌。利用粒径分析软件Nano measure 2.1测量气孔的尺寸,分析各类气孔的形成机制。结果表明:随激光功率的增大,熔合区气孔率增大;微观气孔内壁光滑、呈倒喇叭形,属于氢致气孔;粗大宏观气孔形状不规则,内壁粗糙,具有明显的金属冲涮痕迹,是遗传于母材预存的气缩孔,建立了重熔区气孔体积同熔池气泡体积内在关联的数学模型。
In order to study the formation mechanism of pores in die-casting magnesium alloy fusion welding process, laser remelting of AZ91D die-casting magnesium alloy with thickness of 6mm was carried out. The microstructure and stomatal morphology of the parent material were observed by optical microscope (OM) and scanning electron microscope (SEM). The size of stomata was measured by Nano measure 2.1, and the formation mechanism of stomata was analyzed. The results show that the porosity of the fusion zone increases with the increase of laser power. The inner wall of the microscopic stoma is smooth and inverted flare, which belongs to the hydrogen induced porosity. The coarse macro stomatal shape is irregular and the inner wall is rough with obvious traces of metal rushing. Is a pre-stored shrinkage cavity inherited from the base metal. A mathematical model is established to correlate the pore volume in the remelting zone with the bubble volume in the weld pool.