MONODISPERSED AL3(LiScZr) CORE/SHELL NANOSTRUCTURES EMBEDDED IN Al-RICH MATRIX

V. Radmilovic
National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, University of California, One Cyclotron Rd., Berkeley, CA, 94720, USA

Al-Sc-Zr alloys are extremely resistant to recrystallization due to coherent L12 core/shell precipitates consisting of an Al3Sc core surrounded by a Zr-rich shell. By adding Li to this ternary alloy, we demonstrate a way of producing monodispersed Al3(LiScZr) core/shell inclusions 32.1±1.9 nm in diameter, as observed by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). By combining high resolution phase contrast and high angle annular dark field (HAADF) imaging with energy dispersive spectroscopy (EDS), electron energy loss spectroscopy (EELS) and spectrum imaging, it was found that precipitates consist of a Li- and Sc-rich core surrounded by a Li-rich shell thick 9.2±0.8 nm, with Zr segregating at the core/shell interface. A uniform distribution of particles can be made reproducibly by exploiting kinetic and thermodynamic parameters. This approach to generating precipitate distributions can be applied to a range of alloys and could lead to new types of dispersion-strengthened materials.