电场对AZ31B与Al连接界面扩散反应和扩散溶解层结构的影响

Influence of electric field on interfacial diffusion reaction and microstructure of diffusion dissolution layer of AZ31B/Al joint

应用电场激活扩散连接技术(FADB)实现AZ31B与Al的连接。研究了电场对AZ31B/Al结合界面扩散反应和扩散溶解层结构的影响。采用光学显微镜、扫描电子显微镜、X射线能谱与X射线衍射仪等方法分析了扩散溶解层的显微组织、相组成和元素分布。结果表明,在FADB条件下以铝粉为中间层时扩散溶解层由均匀共晶层、过渡层和胞状晶组成;以铝箔为中间层时由镁合金侧共晶层和铝侧过渡层构成。电场强度对扩散溶解层宽度和形态均有显著影响。溶解层随电流密度升高而变宽。以铝粉为中间层在温度450℃,时间50min,电流密度80A·cm-2时过渡层宽度为120μm,为未施加电场时的12倍。电流对共晶层内晶粒尺寸有显著影响。当电流密度由28A·cm-2升至48A·cm-2时,点状晶粒晶粒尺寸由2μm降至0.5μm。

Interfacial diffusion reaction and structure of Mg-Al diffusion dissolution layer at interface of AZ31B/Al joints prepared by electric field-activated diffusion bonding（EFADB）process using aluminum powder and aluminium foil as intermediate layer, respectively, were investigated. The microstructure, phases and component distribution of the Mg-Al diffusion dissolution layer were analysed by means of optical microscope, SEM, EDS and XRD. The results show that when the intermediate layer is aluminum powder the diffusion dissolution layer is composed of eutectic layer, transition layer and cellular crystal layer, and the dissolution layer consists of eutectic layer and transition layer when the intermediate layer is aluminum foil. The morphology and width of the diffusion dissolution layer are significantly affected by the electric field intensity. When the current density is 80 A·cm^-2 , the thickness of the transition layer is 120 μm, which is 12 times of that at current-free condition for the AZ31B/Al joint prepared at 450 ℃ for 50 min using aluminum powder as the intermediate layer. The grain size of the eutectic layer decreses from 2 μm to 0.5 μm when the current density increases from 28 A·cm^-2 to 48 A·cm^-2 .