Orientation-Dependent Dissolution of Iron Whiskers

The dissolution kinetics of iron filamentary single crystals in dilute acidic environments were shown to obey the topographical theorems proposed by Frank to describe etch-rate anisotropy. Successive dissolution profiles of iron whiskers were observed in situ. by using time-lapse motion picture photomicroscopy. Reluctance diagrams constructed from these dissolution shapes agreed very favorably with experimentally measured dissolution rates and in this way demonstrated the validity of Frank's theory to metallic substrates. A three-dimensional reluctance surface for iron whiskers having 〈111〉 growth axes inferred from the experimental data was consistent with known relative magnitudes of anisotropic dissolution rates; in fact, the reluctance plots constructed according to the kinematic theory were seen to be two-dimensional sections of this surface.