Preparation and properties of copper-aluminum composite strips and foils by horizontal continuous composite casting and rolling

Abstract

Cu-Al composite strips and foils show broad application prospects in electric power, new energy and other fields. However, they are difficult to prepare because of brittle interfacial intermetallic compounds and deformation ability difference between two matrix metals. In this study, Cu-Al composite strips and foils with the thickness of 350 µm and 50 µm are successfully prepared by horizontal continuous composite casting and rolling. Moreover, the effects of as-cast interfacial layer thickness on the properties of Cu-Al composite strips are studied. In the rolling, the as-cast interfacial layer is broken into fragments, so as to promote the Cu-Al matrix bonding at atomic scale. The local solid-state amorphous transformation is also observed at the newly formed Cu-Al interface. Therefore, with the as-cast interfacial layer thickness decreasing from 400 µm to 25 µm, the peeling strength of Cu-Al composite strips increasing from 15.1 N/mm to 17.5 N/mm. With the as-cast interfacial layer thickness decreasing from 400 µm to 65 µm, the conductivity of Cu-Al composite strips increases from 62.36%IACS to 72.58%IACS because the size of interfacial layer fragments is reduced. However, with the as-cast interfacial layer thickness decreasing from 65 µm to 25 µm, the conductivity decreases from 72.58%IACS to 68.65%IACS because the copper layer thickness after rolling is reduced. Large interfacial layer fragments hinder current conduction, but a suitable interfacial layer thickness can inhibit the coordinated deformation of Cu and Al, so as to increase the proportion of copper layer thickness in the entire composite strip.