Cu–Al interfacial compounds and formation mechanism of copper cladding aluminum composites

Copper cladding aluminum (CCA) rods with the section dimensions of 12 mm in diameter and 2 mm in sheath thickness were fabricated by vertical core-filling continuous casting (VCFC) technology. The kinds and morphology of interfacial intermetallic compounds (IMCs) were investigated by SEM, XRD and TEM. The results showed that the interfacial structure of Cu/Al was mainly composed of layered γ1(Cu9Al4), cellular θ(CuAl2), and α(Al)+θ(CuAl2) phases. Moreover, residual acicular ɛ2(Cu3Al2+x) phase was observed at the Cu/Al interface. By comparing the driving force of formation for ɛ2(Cu3Al2+x) and γ1(Cu9Al4) phases, the conclusion was drawn that the ɛ2(Cu3Al2+x) formed firstly at the Cu/Al interface. In addition, the interfacial formation mechanism of copper cladding aluminum composites was revealed completely.