Atom probe studies of metallic glasses

Atom probe tomography was used to characterize the distribution of atoms in bulk amorphous Pd₄₀Ni₄₀P₂₀, Pd₄₀Ni_40-xFe_xP₂₀ (0<x<20), and (Pd₅₀Cu₅₀)_100-xP_x (x=16.5, 17.5, 19) alloys. The analyses were performed on samples cut from 7-mm diameter rods, which were prepared by quenching the melt at cooling rates of approximately 200 K/s. All the alloys were examined in the as-quenched condition. In the Pd₄₀Ni_40-xFe_xP₂₀ glasses, the increase in Fe concentration causes a systematic increase in the clustering of palladium and ordering of phosphorus. The 20% Fe alloy exhibited a two-phase microstructure. The (Pd₅₀Cu₅₀)_100-xP_x glasses exhibited fine-scale phase separation into copper-enriched/phosphorus-depleted and copper-depleted/phosphorus-enriched regions. These observations follow from statistical analysis of the concentration frequency distributions, the composition enrichments of shells around each atom, and composition maps.