填充材料及稀土对压铸镁合金TIG焊接气孔的影响  

Influences of Filler Materials and Rare Earths on Porosity in Gas Tungsten Arc Welding of Die Casting Magnesium Alloy

作　　者：游国强[1,2] 杜娟[1] 杨明华[1] 王向杰[1] 龙思远[1,2] 

机构地区：[1]重庆大学,重庆400044 [2]国家镁合金材料工程技术研究中心,重庆400044

出　　处：《稀有金属材料与工程》2014年第3期641-645,共5页Rare Metal Materials and Engineering

基　　金：国家自然科学青年基金项目(51105393);中央高校基本科研业务费项目(CDJXS11132226);重庆市科技攻关项目(CTCS2010AA4045);重庆大学大型仪器设备开放基金项目(2012121505)

摘　　要：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。The plates of die cast AZ91D magnesium alloy were welded by gas tungsten arc welding （GTAW） with the filler metal of extruded AZ61 as well as AZ61 containing mixed rare earth elements and no filler metal. The porosity in the weldment and the chemical composition of the weld joints were investigated by scanning electron microscopy （SEM） and energy dispersive spectrometer （EDS）. The results indicate that： there were many micropores and macropores around the fusion line in all welded specimens, and it is proposed that the former were mainly induced by hydrogen, while the latter were inherited from the porosity that were mainly nitrogen preexisting in the base metal. The amount of porosity in the weldment welded with AZ61 wire was less than that without filler metal, and the size of large pores was also decreased, which was the effect of dilution due to less gas inclusions in the filler material. A further decrease of the porosity was observed in the joint using filler wire AZ61 containing rare earths, and the probable mechanisms are following. On the one hand, the rare earth elements reduced effectively the hydrogen-induced porosity by increasing the solid solubility of H in the magnesium alloy, reacting with H to form hydrides and accelerating the escape velocity of bubbles. On the other hand, the porosity that resulted from N2 was decreased to some extent too because the rare earths accelerated the overflow velocity of bubbles.

关 键 词：气孔 压铸镁合金 稀土 填充材料中图法 

分 类 号：TG444.74[金属学及工艺—焊接]