Vertical continuous compound casting of copper aluminum bilayer rods

A vertical continuous compound casting technology for the production of rotationally symmetric bilayer rods consisting of brass CuZn37 and aluminum AA7075 was developed. The interface of the metallurgically bonded semi-finished products was composed of four intermetallic layers and an anomalous eutectic area of Al₂Cu (θ-AlCu), Al solid solution (α-Al), and other intermetallic precipitates. The intermetallic layers were CuZn (β-CuZn), a suggested two-phase region of Al₃Cu₅Zn₂ (τ-AlCuZn) and Cu₅Zn₈ (γ-CuZn), Al₄Cu₃Zn (τ′-AlCuZn), and AlCu (η₂-AlCu). The correlation between the process parameters casting speed, cladding temperature, and tool tempering and the interface formation was studied. The experimental investigations were accompanied by a numerical FEM analysis. The casting speed and the cladding temperature were found to be key factors, that influence the formation of a cohesion between the joining partners.