Influence of oxidation rate and alloy composition on alloy enrichments of anodized Al–W alloys

The effect of oxidation rate on enrichment of tungsten in metastable, solid-solution Al–W alloys during anodizing has been investigated by Rutherford backscattering spectroscopy and medium energy ion scattering. The oxidation rate has negligible influence upon enrichment for current densities in the range 0.01–100 mA cm−2, with levels between 1.3 × 1015 and 1.5 × 1015 W atoms cm−2 for an Al–0.7at.%W alloy. Further, enrichment factors, expressing the ratio of the enrichment of tungsten in the alloy, in units of 1015 atoms cm−2, to the bulk composition of the alloy, in units of at.%, for alloys of compositions in the range 0.1–30 at.%W, decrease progressively in the approximate range 2.5–0.2.