A high-resolution scanning Auger micropobe analysis was carried out on matching fracture surfaces of symmetrical Σ = 5 (013) bicrystals of Fe-3 wt%Si doped with 270 ppm phosphorus which were grown from seeds by floating-zone melting. The phosphorus distribution on some regions of a fracture surface was found to alternate between high and low concentrations; these alternations were often associated with deformation bands, such as mechanical twins. The reverse pattern was found on the matching region on the opposite fracture surface. This confirms a hypothesis made earlier that the inhomogeneous phosphorus concentrations found on fracture surfaces are the result of off-center crack propagation through a laterally extended phosphorus distribution along the grain boundary and the switching of the crack path from one side to the other upon an encounter with a grain-boundary step caused by a deformation band. In the regions of unequal division of the P-enriched region by the fracture, a 2:1 ratio of phosphorus concentrations was found. The total width of the region was deduced to be about five atomic planes from observations of sputtering rates and an analysis based on simple logic.
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