焊接电流对铝/镀锌钢TIG焊接头显微组织与力学性能的影响

摘要

本文采用TIG熔-钎焊焊接方法,以Al-Si12为填充材料,将6061铝合金与HSLA350镀锌钢以搭接方式进行连接.本试验用扫描电子显微镜(SEM)、电子背散射衍射(EBSD)、X射线衍射仪(XRD)和能谱仪(EDS),对40 A、60 A和80 A三种不同电流下焊接接头的显微组织进行表征,并测试了接头的力学性能,分析电流大小对焊接接头显微组织和力学性能的影响.结果表明:铝合金能与镀锌钢形成连接良好的接头,焊接电流40 A时接头结合不牢固,焊接电流80 A时接头内形成了更多的硬脆相,力学性能降低.焊接电流60 A时接头性能最佳,为188.4 MPa,可达6061铝合金母材的71%;在铝/钢TIG焊接接头界面处形成了铁、铝异种金属间化合物,靠近铝一侧形成较厚一层FeAl3金属间化合物,靠近钢一侧形成了较薄Fe2 Al5金属间化合物层,还伴随有少量的Fe3 Al生成.%A tungsten inert gas ( TIG) welding-brazing technology using an Al-Si12 based filler was developed for joining aluminum alloys to HSLA350 galvanized steel. The microstructures of welded joints under different current of 40 A, 60 A and 80 A were characterized by scanning electron microscopy ( SEM) , EBSD, X-ray diffraction ( XRD) and energy dispersive spectrometer ( EDS) , and the mechanical properties was tested. The effects of current on the microstructures and mechanical properties of Mg / steel joints were investigated. The results show that the acceptable joint between Al alloysandgalvanized steelis obtained. When the welding current is 40 A, the joint is not strong. When the welding current is 80 A, the joint has more hard brittle phases and the mechanical properties are reduced. When the welding current is 60 A, the joint has the best performance of 188. 4 MPa, representing 71% joint efficiency relative to Al6061 base material. In the Al/steel TIG welded joint interface, the iron and aluminum dissimilar intermetallic compounds have formed. Close to the aluminum side forms a thick layer of FeAl3 intermetallic compound while near the steel side forms a thin layer of Fe2 Al5 intermetallic compound, accompanied by the small amounts of Fe3 Al.