Erbium and ytterbium solubilities and diffusivities in aluminum as determined by nanoscale characterization of precipitates

Binary aluminum alloys with 0.03–0.06 at.% RE (RE = Yb or Er) were aged to produce coherent, nanosize Al₃RE precipitates in an α-Al matrix. The temporal evolution of precipitate radii and matrix concentrations at 300 °C were measured by transmission electron microscopy and local-electrode atom-probe tomography, respectively. The temporal dependence of the matrix concentration of each RE was utilized to determine its solubility in Al. The solubility and the coarsening rate constants were used to determine the diffusivity of each RE in α-Al and the α-Al/Al₃RE interfacial free energies at 300 °C. When compared to Sc, both Yb and Er exhibited smaller solubilities but larger diffusivities in α-Al and larger α-Al/Al₃RE interfacial energies.