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

Abstract

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).