Effect of edges and corners on stresses in thermally grown alumina scales

Residual stress near edges and corners of thermally grown alumina scales we re investigated. In this study, an edge is the intersection of two orthogon al flat surfaces and LI cor ner is the intersection of three such surfaces. Microfluorescence measurements, performed On alloys with composition Fe-28 Al-5Cr (at.% bal Fe) oxidized at 900 degrees C, showed a large (>50%) reduc tion in hydrostatic stress in the vicinity of edges and corners. Surprising ly, significant stress reduction persists out to distances twenty to fifty times the scale thickness from the edge. Finite-element analysis calculatio ns confirm the experimental results and provide a considerably moi e detail ed picture of the stress distribution and its components and show that much Of the observed stress reduction near an edge, is due to plastic deformati on of the underlying metal.