In situ HRTEM observation of solid-liquid interfaces

The processes of melting and freezing of alumina, Al and Al-Si alloy have been observed directly in a conventional transmission electron microscope (CTEM). The solid-liquid and solid-solid interfaces in these materials have been observed at an atomic level. The liquid phase nucleated preferentially at the surfaces of the Al particles at the melting. The liquid phase then propagated into the interior of the Al particles at the expense of the solid. The solid-liquid interface of alumina showed the atomically flat interface. The layer-by-layer growth of alumina on the solid-liquid interface was observed. The solid-liquid interface in an Al-Si alloy was atomically flat, while the solid-solid interface was atomically rough. When Al melted, the surface of Si particle showed characteristic reconstructed structures.