Characteristics and Formation Mechanism of the Interface of Mg/Al Bimetallic Composites Prepared by Lost Foam Casting

摘要

In the present work, the Mg/Al bimetallic composites were successfully prepared by the lost foam casting (LFC) process, and the characteristics and formation mechanism of the interface of the Mg/Al bimetallic composites were investigated. The results show that a uniform and compact metallurgical interface with an average thickness of about 1400 μm was formed between magnesium alloy and aluminum alloy. The interface layer of the Mg/Al bimetallic composites was composed of three different reaction layers, namely the Al_(12)Mg_(17)+δ(Mg) eutectic layer adjacent to the magnesium matrix, the Al_(12)Mg_(17)+Mg_(2)Si interlayer and the Al_(3)Mg_(2)+Mg_(2)Si layer close to the aluminum matrix. The microhardnesses of the interface layer were remarkably higher than those of the magnesium and aluminum matrixes. The stress strength of the Mg/Al bimetallic composites was up to 47.67 MPa. The fractograph of the push out sample mainly showed a brittle fracture nature. The formation of the interface of the Mg/Al bimetallic composites was attributed to the fusion and diffusion bonding. With the variations of the concentrations of the different elements at the interface, the Al_(3)Mg_(2 )intermetallic phase first formed near to the aluminum matrix, and then the Al_(12)Mg_(17) and Mg_(2)Si successively generated toward the magnesium matrix, finally obtaining the interface layer of the Mg/Al bimetallic composites.