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

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.