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

Abstract

A nano-precipitate of Si-Mg2Si core–shell structure is identified by the first time in Al alloys. The orientation relationship (OR) between the β-Mg2Si shell and the Si core is 〈001〉β // 〈110〉Si, <1 1¯ 0>β // <1¯ 1 1¯>Si, and 〈110〉β // <1¯ 12>Si, which can be predicted by near row matching model based on interfacial good matching. It also predicts (1 1¯ 0)β // (1¯ 1 1¯)Si to be a preferred interface, which contains the two matching rows of 〈001〉β // 〈110〉Si and 〈110〉β // <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.