Atomistic study of atomic structures and dislocation nucleation at Al/Al₂Cu interfaces

The plate-like phase of Al₂Cu necessitates a detailed understanding of the interface structure, which significantly governs the structural applications of Al-Cu alloys. Different from a metal/metal interface where only one stable interface exists, the metal eutectic composites possess multiple possible interfaces. Here, atomistic simulations were implemented to reveal a strong dependence of dislocation structure on the termination plane at the Al/Al₂Cu hetero-interface. Different termination of Al₂Cu phase at interfaces exhibited distinct atomic arrangements, leading to variations of ^_γ -surface and ultimately dictate the dislocation structure. Among the four possible termination at Al₂Cu (110) plane, two of them are stable in Al/Al₂Cu hetero-interface, named as Al_B-terminated and Al_A2-terminated interfaces. The networks of misfit dislocations with different Burgers vectors of these two interfaces are also identified. Disregistry investigations of the interface showed that the misfit dislocation lines in Al_B-terminated interface are curved while that in Al_A2-terminated interface are straight. This is related to the relative interface energy between the stable coherent structures. These dislocation networks in turn have a bearing on the mechanical response of interfaces, as manifested by the different nucleation mechanisms of lattice dislocations. Although this work is performed on a particular Al/Al2Cu, the commonalities also exist in other eutectic composites. The detailed correlation between the interface structure and termination at metal-intermetallic interface has been recognized for the first time, which could offer novel avenues for fine-tuning eutectic composites with enhanced properties.