Orientation relationship prediction and interfacial structure of a nano-scale Si-Mg2Si core-shell precipitate in an aluminum alloy

A nano-precipitate of Si-Mg2Si core-shell structure is identified by the first time in Al alloys. The orientation relationship (OR) between the ss-Mg2Si shell and the Si core is < 001 > (ss) // < 110 >(Si), < 1 1 0 > (ss) // < 1 1 1 >(Si), and < 110 > (ss) // < 1 12 >(Si), which can be predicted by near row matching model based on interfacial good matching. It also predicts (1 1 0) (ss) // (1 1 1) Si to be a preferred interface, which contains the two matching rows of < 001 > (ss) // < 110 >(Si) and < 110 > (ss) // < 1 12 > Si. First-principles calculation of interfacial energy reveals that heterogeneous nucleation of Mg2Si on Si is favored due to reduction of nucleation barrier.