Nanometer-scale solute clustering in aluminum!/nickel!/ytterbium metallic glasses

The transformation sequence of melt-spun Al!/5.2at.% Ni!/6.8at.% Yb is characterized by X-ray diffraction, differential scanning calorimetry (DSC), and atom-probe field-ion microscopy. An isochronal DSC thermogram detects three major exothermic transformation steps, with onset temperatures of 180, 292, and 327 8C, respectively. Atom-probe analyses reveal the evolution of compositional inhomogeneities on an atomic scale. In addition to Ni!/clusters present in the as-quenched alloy, Ni!/Yb co-clusters form during isochronal heating to 188 8C. Al!/rich precipitates are detected after heating to 250 8C, with the Ni and Ni!/Yb clusters still present, constituting possible precursors of intermetallic phases formed during advanced transformation stages. # 2002 Elsevier Science B.V. All rights reserved.