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采用挤压态AZ61镁合金和含有富钕(Nd)混合稀土元素的AZ61镁合金焊丝作填充材料对压铸AZ91D镁合金进行TIG填丝焊。为了对比焊缝气孔倾向,同时对压铸AZ91D镁合金进行了自熔焊接。采用扫描电镜(SEM)观察焊缝气孔形貌和分布,利用X射线能谱(EDS)仪分析焊缝成分。结果表明:在熔合线附近存在明显的微观和宏观气孔,前者应该主要为氢气孔,后者应该主要为遗传于母材的氮气孔;采用含气量低的挤压态AZ61作填充材料,能够较明显地降低焊接接头的气孔率,减小粗大气孔的尺寸和数量,应该是填充材料对熔池中气体的稀释作用所致;采用含富钕混合稀土的AZ61作填充材料,能够进一步降低焊接接头的气孔率,这应该是由于:富钕混合稀土通过增加镁合金对H的固溶度、与H反应生成稳定的氢化物和提高气泡溢出速度3种机制有效减少了氢气孔,并通过提高气泡溢出速度在一定程度上减少了氮气孔。
AZ91D magnesium alloy die-casting was filtrated with TIG wire by using extruded AZ61 magnesium alloy and AZ61 magnesium alloy wire containing Nd-rich mixed rare earth elements as filling material. In order to compare the stomatal tendency of the weld seam, the die-cast AZ91D magnesium alloy was self-flux welded at the same time. Scanning electron microscopy (SEM) was used to observe the pore morphology and distribution of the weld, and the composition of the weld was analyzed by X-ray EDS. The results show that there are obvious microscopic and macropores in the vicinity of the fusion line, the former should mainly be hydrogen pores, and the latter should mainly be nitrogen pores inherited from the parent material. Using compressed air with low content of AZ61 as filling material, Obviously reduce the porosity of the welded joints, reducing the size and number of coarse pores, the filler should be due to dilution of gas in the molten pool caused by the use of neodymium-rich mixed rare earth AZ61 filler, can further reduce the welded joints Of the porosity, which should be due to: Neodymium-rich mixed rare earth by increasing the solid solubility of magnesium alloy H, H and the reaction with the formation of stable hydride and improve the bubble overflow rate of three mechanisms effectively reduce the hydrogen pores, and by increasing the bubble Spillage speed to a certain extent reduced the nitrogen hole.