Experimental and first-principles characterization of heterogeneous nucleation of η on the E(Al18Mg3Cr2) phase in the 7075 Al alloys

Abstract

In this work, the heterogeneous nucleation process in the early ageing period is systematically analyzed by means of electron microscope images and phase transition crystallography calculations with a near-row matching model, which illustrate the phenomenon that the surface of the E phase directly nucleates the equilibrium phase η instead of following the ageing sequence. It is found that the structures of E phase and η phase at the interface have high similarity, and atom matching can be realized in several crystal directions and crystal planes. Through a combination of experimental observation and first-principles, HAADF-STEM images from three different E/η interfaces are characterized in detail, and they are found to belong to three different views of the same orientation relation (OR), while the segregation behavior at such E/η interfaces is calculated. By calculating and analyzing interfacial properties at the atomic level, this basic data will be useful for more in-depth analyses in the future, as well as facilitating the design and updating of materials.