Analysis of liquid–solid interface bonding behaviour of 7075 aluminium alloy/SiCp reinforced aluminium base alloy

Abstract

The introduction of heterogeneous elements and the presence of the oxide layer on the surface of aluminum alloy usually play a negative role in the interfacial bonding of Al/Al bimetallic composites. To solve these two key problems of interfacial bonding of bimetallic composites. This work proposes to composite SiCp/7075(solid)-7075 alloy(liquid). The main alloying element Zn of 7075 alloy is selected to perform hot dip treatment on SiCp/7075(solid) to reduce the influence of the oxide layer on the surface of the aluminum alloy and the introduction of heterogeneous elements. Al/Al bimetallic composites were prepared by using a hot-dip/non-hot-dip zinc + liquid–solid composite casting process. The bimetallic composite interfacial bonding of SiCp/7075–7075 matrix alloy was studied. The results revealed that an oxide layer existed at the interface of the bimetallic composite upon preheating at 400–475 °C and hot dipping at 400–425 °C. With an increase in the hot-dip temperature, the interface oxide layer disappeared because of the combined effect of thermal expansion deformation, lower solidus temperature of the zinc-rich layer, and volume expansion of the solid–liquid phase transition. Metallurgically bonded interfaces were obtained at the hot-dip temperatures of 450 and 475 °C. The fracture location was on the SiCp/7075 Al matrix composite side, showing that this composite's interfacial bond strength was higher than that of the SiCp/7075 Al matrix composites. The results of this study provide a new idea for the preparation of lightweight wear-resistant Al/Al bimetallic composites by liquid-solid composite casting.