Effect of vibration on interfacial microstructure and mechanical properties of Mg/Al bimetal prepared by a novel compound casting

In this work, a vibration was applied in the preparation of the Mg/Al bimetal by a novel compound casting in order to improve the mechanical properties of the Mg/Al bimetal, and the effect of the vibration on the interfacial microstructure and mechanical properties of the Mg/Al bimetal was investigated. The results indicated that the vibration had a significant effect on the interfacial microstructure and mechanical properties of the Mg/Al bimetal, but it did not change the phase compositions of the interface, which was composed of layer I (Al3Mg2+Mg2Si), layer II (Al12Mg17+Mg2Si) and layer III (Al12Mg17/δ-Mg). Without vibration, the Mg2Si phase with a needle-like morphology mainly aggregated in the layer II of the interface. After the application of the vibration, the SEM and EBSD analysis results showed that the Mg2Si and Al3Mg2 phases in the interface were obviously refined, and the distribution of the Mg2Si became more uniform, due to the strong forced convection of the molten metal resulting from the vibration. The TEM analysis indicated that the interface between the Al3Mg2 and Mg2Si phases was non-coherent, suggesting the Mg2Si particles cannot act as a heterogeneous nucleation base during the solidification process of the interface. Compared to the Mg/Al bimetal without vibration, the shear strength of the Mg/Al bimetal with vibration increased by about 50% from 31.7 MPa on average to 47.5 MPa, and the hardness of the layer I of the interface increased, and the hardness of the layer III decreased. The fracture surface transformed from a flat fracture morphology without vibration to an irregular zigzag fracture morphology.