An investigation into interface formation and mechanical properties of aluminum–copper bimetal by squeeze casting

Highlights: • Al–Cu bimetal was firstly produced by compound casting with squeeze casting method. • Thermal spray Zn coating was introduced to protect solid Cu substrate. • Al₄Cu₉, Al₂Cu, Al–Cu eutectic and Al solid solution were verified in interface. • Sound metallic bonding with high mechanical and electrical properties was produced. Aluminum–copper bimetal was prepared by compound casting liquid aluminum onto copper bars and solidifying under applied pressure. The effect of pouring temperature and applied pressure on microstructure and mechanical and electrical properties of the bimetal was investigated. Bonding mechanism and mechanical and electrical behaviors of bimetal were analyzed. Sound metallurgical bonding could be achieved by applying thermal spray zinc coating onto Cu inserts and carefully controlling the squeeze casting process. The results showed that interfacial reactions between liquid Al and solid Cu lead to the formation of transition zone, four possible layers, Al₄Cu₉ layer, Al₂Cu layer, Al–Cu eutectic layer and Cu rich Al solid solution layer were identified in the transition zone. The thickness of each layer varies with the variation of pouring temperature and applied pressure. The formation of inherent defects and thickening of intermetallic compound promotes cracks propagation and weakens the bonding strength, hinders current flowing through and weakens the electrical property. The bimetal made at pouring temperature of 700 °C gives the best mechanical and electrical properties.