AbstractMicroscopic examination of the surface of single crystal (111) NiAl during various stages of oxidation at 1100 C in air shows the development of islands composed of rings of different colors.These islands appear to grow in size and eventually impinge with increased exposure. Microscopic fluorescence mapping of the surfaces of three single crystals subjected to varied exposure times provides an identification of the composition of the islands and the surrounding area as two different allotropes of alurninum oxide.Additionally, analysis of the map spectra demonstrates the decrease of intensity of their characteristic fluorescence bands in the island centers with increasing island size, which we refer to as “volcanic” intensity topography. Thus, the observed color variation is an interference effect, due to varied films thicknesses through the islands. Finally, the energies of the fluorescent bands are seen to shift as a function of distance from the island center, indicating the development of strain gradients across the islands.
Numerical modelling of micro-machining of f.c.c. single crystal: Influence of strain gradients
