Thermal Properties of Intermetallic Phases at the Interface of Aluminum–Copper Compound Castings

Abstract

High‐pressure die compound casting relies on high bond quality, and high thermal contact conductance at the interface is a key issue in the context of cast advanced cooling components, such as lightweight heat sinks for desktop and portable computers. The current study aims at enhancing the thermal contact between a copper insert piece and an AlSi9Cu3(Fe) cast alloy by developing suitable Zn‐based coatings, which are used to establish a firm metallurgical bond between the solid insert and the cast alloy during high‐pressure die‐casting. It is demonstrated by microstructural analyses that various phases form at the interfaces in the casting process. As the thermal conductivities of these phases have not been available, these are determined individually using a thermoflash device. The SEM investigations indicate that mainly ternary phases of the type AlxCuyZnz emerge in the bonding zone, as the high casting temperatures promote the diffusion of aluminum atoms into the coating. Interestingly, an alloy containing 50 wt% zinc reaches a thermal conductivity as high as 166 W mK−1. The microstructural characteristic at the interfaces and the ramifications with respect to applications are discussed.