MB2-LY12扩散焊接头界面组织结构及其形成机制

采用真空扩散焊接技术进行镁合金（MB2）与铝合金（LY12）的焊接,采用超声波无损检测,电子探针、X射线衍射和扫描电镜等手段研究了焊接温度对焊接接头界面附近组织结构的影响,分析了界面反应物的生成机理。结果表明,随着焊接温度的升高,焊接界面的焊合率提高,在焊接压力为3 MPa、保温时间为100 min的条件下,温度升高到480℃完全焊合,在Al侧和Mg侧分别形成了A1（ss,Mg）和Mg（ss,A1）固溶体,焊接界面形成了Al₁₂Mg₁₇、AlMg、Al₃Mg₂三种金属间化合物层,其厚度随着焊接温度的升高而增加,其中AlMg层厚度增长得最快,接头断裂发生在金属间化合物层且呈阶梯状断裂。界面扩散区的形成主要由有效物理接触阶段、固溶体形成阶段、金属间化合物相形成阶段以及金属间化合物增长阶段组成。

Structure and Diffusion Mechanism of MB2/LY12 Joint by Diffusion Welding

MB2 alloy and LY12 alloy were welded by vacuum diffusion welding.The element distribution and intermetallic compounds at the interface were characterized by Scanning Acoustic Microscopy, SEM,XRD and EPMA.The results show that the welding interface bonding rate can be improved with the welding temperature,and the welding interface bonding can be achieved completely at the condition of 3MPa,lOOmin and 480℃.The solid solution Al（ss,Mg） and Mg（ss,Al） formed at the interface.Also, Al₁₂Mg₁₇,AIMg and Al₃Mg₂ formed at the interface,where the joint fracture occurred,and the thickness of the intermetallic compounds increase with increase of the temperature.The reaction layers of MB2 and LY12 welding joints can be divided into the following stages:effective physical contact,solid solution generating,intermetallic reaction layer generating,and intermetallic layer growing.