Three-dimensional atomic-scale imaging of impurity segregation to line defects

Clouds of impurity atoms near Line defects are believed to affect the plast ic deformation of alloys. Three-dimensional atom probe techniques were used to image these so-tailed Cottrell atmospheres directly. Ordered iron-alumi num alloys (40 atomic percent aluminum) doped with boron (400 atomic parts per million) were investigated on an atomic scale along the (001) direction . A boron enrichment was observed in the vicinity of an (001) edge dislocat ion, The enriched region appeared as a three-dimensional pipe 5 nanometers in diameter, tangent to the dislocation Line. The dislocation was found to be boron-enriched by a factor of 50 (2 atomic percent) relative to the bulk . The Local boron enrichment is accompanied by a strong aluminum depletion of 20 atomic percent.