Formation of intermetallic compounds of Cu/Al multilayer foils during cold rolling

In metallurgical theory, the generation of new phases requires high temperature diffusion over a long period of time. Here, we report an experimental study of the generation of new phases using large mechanical deformations and high pressure, rather than heat. A 4.83-mm-thick 23-layered Cu/Al sandwich strip was formed by cold rolling. When the Cu/Al sandwich was further rolled to a 0.13-mm-thick foil on a four-high micro-foil mini mill at room temperature, some rectangular-shaped phases appeared at the Cu/Al interfaces. The scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analyses reveal that the phases are a mixture of Al2Cu/AlCu/Al4Cu9, which indicates that chemical reactions occur at the Cu/Al interfaces during cold deformation. This study provides new insights into the design and development of composite materials for various applications.