钢/铝异种合金激光深熔焊接头界面金属间化合物的EBSD研究

EBSD Investigation of Intermetallic Compounds at Interface of Steel/Aluminum Dissimilar Alloy Joints Produced by Laser Keyhole Welding

以6mm厚钢/铝合金对接接头为研究对象,进行了无任何填充材料的激光深熔焊接的工艺实验,通过调控焊接工艺参数,获得了良好焊缝成形的冶金结合接头。利用光学显微镜(OM)和电子背衍射散射(EBSD)分析方法,研究了不同激光偏移量及接头不同位置对界面金属间化合物(IMC)组织形态、物相组成及厚度的影响。结果表明:钢/铝异种合金激光深熔焊接头界面IMC组织主要由η-Al_5Fe_2及θ-Al_(13)Fe_4两相组成。激光偏移量的大小不仅影响接头界面IMC层的平均厚度,还影响界面IMC晶粒的尺寸:增加激光偏移量显著地减少了接头界面粗大针状θ-Al_(13)Fe_4相数量,细化了接头界面η-Al_5Fe_2层的晶粒,降低了接头界面η-Al_5Fe_2层平均厚度。就接头界面不同位置而言,在两种激光偏移量条件下,接头界面中部η-Al_5Fe_2层的晶粒尺寸和平均厚度最小。此外,从EBSD的相分布研究还发现,接头界面处清晰地显示了在钢基体与η-Al_5Fe_2层之间有θ-Al_(13)Fe_4相的形成。

A laser keyhole welding process was performed to join of 6 mm thick aluminum（Al）alloys to steel plates in a butt configuration without any filler materials.High quality metallurgical bonding joints were produced by controlling welding parameters.The effect of different laser beam effsets and different locations of joints on the morphology,phase components and thickness of the intermetallic compound（IMC）layers was investigated by using optical microscope（OM）and electron backscatter diffraction（EBSD）analysis technology.The results show that the main phases of IMC layers are composed of η-Al5Fe2 and θ-Al（13）Fe4 phases.The laser beam offsets have an important influence not only on the average thickness of IMC layers but also on the IMC grain size：increasing laser beam offsets significantly reduces the amount of needle-like θ-Al（13）Fe4 phases,refines the grain sizes of η-Al5Fe2 layers,and decreases the average thickness of η-Al5Fe2 layers at the interfaces.In considering the influence of the different locations through the steel/Al alloy joint,under the conditions of two laser beam offsets,the minimum grain size and thickness of η-Al5Fe2 layers have been obtained at the middle part of the steel/Al alloy joints.In addition,it shows clearly that the θ-Al（13）Fe4 phases are generated between the η-Al5Fe2 layers and the steel substrates are confirmed by the EBSD phase analysis.