Phase stability and the interface structure of a nanoscale Si crystallite in Al-based alloys

Abstract

An atomic-scale understanding of the role of strain on the microstructural properties of nanoscale precipitates will be helpful to explore the precipitation behavior as well as the structure–property relationships in crystalline multi-phase systems. Nanoscale Si precipitates are formed in Al-based alloys prepared by selective laser melting. The phase structure and the nature of heterointerface have been characterized using advanced electron microscopy. The nanocrystalline Si mainly contains two polymorphs, diamond-cubic Si (DC-Si) and 4H hexagonal Si (4H-Si). Heteroepitaxy occurs at the DC-Si(111)/Al(100) and 4H-Si(0001)/Al(100) interfaces in terms of a coincidence-site lattice model. The nanocrystalline Si undertakes tensile strain superposed by the matrix through heterointerfaces, facilitating the formation of 4H-Si in the nanoscale crystallite, which provides a strategy for designing Si polymorphic materials by strain engineering.