Exploring Microstructure–Physical Property–Corrosion Response Relationship in Intermetallic Compounds of Al-Cu Bimetallic Interfaces

Microstructure, hardness, physical properties, and corrosion response of Al-Cu intermetallic compounds (IMCs) are investigated with the aim of establishing optimization guidelines for the Al-Cu bimetallic compound casting process. Five Al-Cu samples with chemical compositions promoting stable single phases ((Formula presented.) and (Formula presented.) at ambient temperature are produced via induction casting. The microstructural and compositional analysis, however, evidenced the precipitation of secondary phases in the (Formula presented.) and θ samples. It is also observed that θ can directly transform into (Formula presented.), due to a kinetically enabled process. Physical properties, including electrical conductivity, thermal diffusivity, and specific heat, are measured, and the thermal conductivity is calculated accordingly. It is observed that the copper-rich IMCs have lower thermal conductivity compared to other Al-Cu IMCs. The nonmonotonous relationship between physical properties and chemical composition is correlated to the crystallography of the phases and the precipitation of secondary phases. Experimental validation demonstrated a significant impact of casting defects (over 30%) on the thermal conductivity of the interfaces. Moreover, the overall hardness of cast samples showed significant deviation from previous studies, emphasizing the impact of the sample production method. Finally, corrosion assessment using a 0.5% NaCl solution suggested galvanic corrosion as the primary corrosion mechanism.