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 alpha-Al matrix. The temporal evolution of precipitate radii and matrix concentrations at 300 degrees 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 alpha-Al and the alpha-Al/Al3RE interfacial free energies at 300 degrees C. When compared to Sc, both Yb and Er exhibited smaller solubilities but larger diffusivities in alpha-Al and larger alpha-Al/Al3RE interfacial energies. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.