Atomically Resolved Structure of the Directly Bonded Aluminum–Carbon Interface in Aluminum–Graphite Composites by Solid-State Friction Stir Processing: Im plications for a High-Performance Aluminum Conductor

The unique aluminum–carbon interface without carbide, which is termed as the directly bonded aluminum–carbon interface, is a recently reported remarkable structure for simultaneously enhancing the load/electron transfer properties of aluminum conductors. In this paper, the structure of the directly bonded aluminum–carbon interface in aluminum–carbon composites fabricated by solid-state friction stir processing is reported on an atomic scale for the first time. The atomically resolved structure of two typical interfaces, Al-200 | G-end interface and Al-311 | G-side interface, are investigated by using high-resolution transmission electron microscopy. Interfacial distance analysis shows that both interfaces are bonded via chemical bonds, other than van der Waals forces. The Al-200 | G-end interface is found to be in a semicoherent mode, in which every five Al-(200) planes are bonded directly with three basal planes in graphite. Atomically resolved interfacial matching patterns of the Al-311 | G-side interface are proposed based on the observed atomic plane matching relationship. This work provides new insights into the atomic scale of the aluminum–carbon interface for the development of high-performance aluminum conductors.