镁合金电阻点焊接头组织结构特点  

Microstructure of magnesium alloy joints in resistance spot welding

作　　者：郎波[1] 孙大千[2] 任振安[2] 朱百庆 

机构地区：[1]北京航空制造工程研究所,北京100024 [2]吉林大学材料科学与工程学院,长春130025 [3]北汽福田汽车股份有限公司,北京102206

出　　处：《焊接学报》2009年第10期33-36,40,共5页Transactions of The China Welding Institution

基　　金：吉林省科技发展计划(20070309)

摘　　要：为了提高镁合金电阻点焊接头的力学性能,采用光学显微镜、激光共聚焦扫描显微镜、X射线衍射仪研究了接头的微观组织和相组成.结果表明,接头主要由熔核和热影响区(HAZ)所构成.熔核一般包括两种不同的组织形态,即熔核边缘的胞状树枝晶和熔核中心的等轴树枝晶.熔核是由大量的-αMg相和少量的-βMg17Al12相所组成.相对于未熔化的母材晶粒,热影响区晶粒变粗,并伴随晶界熔化.当焊接电流为23 kA,焊接时间为8个周波,电极力为4.5 kN时,熔核边缘的胞状树枝晶细化,而熔核中心的等轴树枝晶有向等轴晶转化的倾向,且平均晶粒尺寸为12.96μm.The microstructure and phase composition of magnesium alloy joints in resistance spot welding are investigated with optical microscopy,confocal laser scanning microscope and X-ray diffraction for improving mechanical properties of the joints.The results show that the joints consist mainly of weld nugget and heat-affected zone(HAZ).The weld nugget contains two different structures,the cellular-dendritic structure at the edge of the nugget and the equiaxed dendritic structure in the center of the nugget.The weld nugget consists of α-Mg phase and a small amount of β-Mg17Al12 phase.Comparing with the grains in no melting base metal,the grains in HAZ become coarse,and the grain boundary melting occurs.Under the condition of 23 kA welding current,8-cycle welding time and 4.5 kN electrode force,the cellular-dendritic structure at the edge of the nugget is refined,and the equiaxed dendritic structure in the central portion of the nugget tends to be changed into the equiaxed grains without secondary axis of crystal with average grain size of 12.96 μm.

关 键 词：镁合金 电阻点焊 微观组织 

分 类 号：TG457.19[金属学及工艺—焊接]