Effects of Melt-to-Solid Volume Ratio and Pouring Temperature on Microstructures and Mechanical Properties of Cu/Al Bimetals in Compound Casting Process

Cu/Al bimetallic composites were fabricated by compound casting where aluminum melts were cast on Ni-coated Cu substrates. Effects of the melt-to-solid volume ratio (VR) and the pouring temperature on interfacial microstructures and mechanical properties of Cu/Al bimetals were investigated systematically. Results show that a continuous and compact interface can be formed when the pouring temperature exceeds 953 K (680 °C). When the VR or pouring temperature increases, the solidification time of α(Al) increases, resulting in an increase in the dissolution content of Cu substrate. The transition zone consists of α(Al) + Al₂Cu eutectic layer and intermetallic compounds (IMCs) layer, and the IMCs are identified as Al₂Cu, AlCu, and Al₄Cu₉. Ni coating participates in the formation of AlCuNi phase between the Al₂Cu layer and AlCu layer when the pouring temperature is 973 K (700 °C). The presence/absence of Ni-containing phase has a close relationship with the dissolution of the Cu substrate. Shear-strength tests show that shear fracture mainly occurs at the hard brittle IMCs layer, and the highest shear strength of 36.01 MPa is obtained for the samples fabricated at 993 K + VR 49.24 (720 °C + VR 49.24).