高频脉冲电流辅助轧焊AZ31B镁合金复合板界面连接机理

Interfacial Bonding Mechanism of AZ31B Magnesium Alloy Composite Plates by Rolling-Welding Assisted with High Frequency Pulse Current

为探究高频脉冲电流作用下金属板复合机理,设计了高频脉冲电流辅助轧焊复合预制缺口镁合金复合板试验。对比不同加载频率(25、50、75 kHz)参数下复合板连接界面和近界面组织演变特征及复合板的力学性能;通过金相显微镜观察近界面微观组织形貌特征;采用纳米压痕仪和维氏硬度计表征连接界面特征微区和横截面硬度分布规律;采用拉伸试验机和扫描电子显微镜进一步对镁合金板材的抗拉强度和断口形貌进行表征分析。结果表明,随着频率的增大,连接界面复合效果呈现先升高后下降的趋势;当高频电流频率为50 kHz时,镁合金复合板的抗拉强度和延伸率最优,分别达到292.52MPa和25.7%。究其原因主要是基于高频脉冲电流的集肤效应、邻近效应、焦耳热效应及界面微区的接触电阻与轧制力耦合作用的结果。

In order to explore the compositing principle of metal composite plates under the high frequency pulse current,the test of rolling-welding with high frequency pulse current on the prefabricated notch of magnesium composite plates was designed.The microstructure evolution and mechanical properties of bonding interface and areas near interface of the composite plates were compared under different loading frequencies(25,50,75 kHz).The morphological characteristics of microstructures near interface of magnesium alloy composite plates was observed by metallographic microscope.Nanoindentation test and Vickers hardness test were used to characterize the hardness distribution of the interface micro-region and cross section.The tensile properties and fracture morphology of magnesium alloy composite plates were analyzed by tensile testing machine and electron microscope.The results show that with the increase in the frequency,the composite effect of the interface increases first and then decreases.When the current frequency is 50 kHz,the tensile strength and elongation of the magnesium alloy composite plates are the best,reaching 292.52 MPa and 25.7%,respectively.This can be contributed to the coupling effect of the skin effect,proximity effect,Joule heat effect,and the coupling effect of the contact resistance in the micro-region of the interface and the rolling force.