Direct Observation of Heterogeneous Nucleation in Al-Si-Cu-Mg Alloy Using Transmission Electron Microscopy and Three-dimensional Atom Probe Tomography

Abstract

The heterogeneous nucleation of the θ’ phase on nanoscale precipitates has been investigated using a combination of three-dimensional atom probe tomography and high-resolution transmission electron microscopy. Two types of θ’ phases were observed, namely small (~2 nm thick) cylindrical precipitates and larger (~100 nm) globular precipitates and both appear to be heterogeneously nucleated on the nanoscale precipitates. The composition and crystal structure of precipitates were directly analyzed by combination of two advanced characterization techniques.