Interface characteristics of Mg/Al bimetal produced by a novel liquid-liquid compound casting process with an Al interlayer

Abstract

Mg/Al bimetal was successfully prepared using a novel lost-foam casting (LFC) liquid-liquid compound process with an Al interlayer, and the interface characteristics including microstructure, mechanical properties, and fracture behavior of the Mg/Al bimetal were investigated in this paper. The results show that the mixing of AZ91D and A356 liquid metals was fully avoided by using the Al interlayer. A metallurgical bonding between the AZ91D alloy matrix and the A356 alloy matrix was achieved, obtaining a compact interface. The interface was constituted by the Al12Mg17 + δ (Mg) eutectic and the Al3Mg2 and Mg2Si reaction layers, which were respectively next to the AZ91D alloy matrix and the A356 alloy matrix. The reaction layers had much higher microhardnesses compared with the microhardnesses of the matrixes, and the highest microhardness up to 275–299 HV was obtained in the reaction layer next to the Al matrix. A brittle fracture morphology was observed in the fractured surface of the Mg/Al bimetal, and the fracture mainly initiated with the fracture of the reaction layer close to the Al matrix.