Development of high strength Mg/Al bimetal by a novel ultrasonic vibration aided compound casting process

Ultrasonic vibration was proposed to enhance interface bonding of Mg/Al bimetal prepared by a novel lost foam compound casting (LFCC) to obtain high strength Mg/Al bimetal. The results showed that the interface of the Mg/Al bimetal without ultrasonic vibration was mainly composed of layer I (Al3Mg2 + Mg2Si), layer II (Al12Mg17 + Mg2Si), and layer III (Al12Mg17 + delta-Mg eutectic). Under the ultrasonic vibration, the Mg2Si and Al12Mg17 phases and the Al12Mg17 + delta-Mg eutectic at the interface were remarkably refined. After the ultrasonic vibration was applied, the Mg2Si phase was uniformly dispersed in the whole interface, and the continuous oxidation inclusion defect was eliminated. As a result, the microhardness of the entire interface became more uniform, and the shear strength of the Mg/Al bimetal significantly increased by 86.5 %, reaching 69 MPa, compared to the bimetal without ultrasonic vibration. The fracture surface of the Mg/Al bimetal without ultrasonic vibration exhibited an apparent brittle fracture morphology. Under the assist of the ultrasonic vibration, the shear strength of the bimetal was improved mainly due to the refinement of the interfacial microstructure, and the fracture surface of the Mg/Al bimetal generated a partial plastic deformation in the interface layer.