Three-dimensional atomic-scale imaging of impurity segregation to line defects
Clouds of impurity atoms near line defects are believed to affect the plastic deformation of alloys. Three-dimensional atom probe techniques were used to image these so-called Cottrell atmospheres directly. Ordered iron-aluminum 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 dislocation. 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.
Blavette
D
Sonde Atomique et Microstructures, Groupe de Metallurgie Physique, UMR CNRS 6634, Faculte des Sciences de Rouen, Universite de Rouen, 76821 Mont-Saint-Aignan Cedex, France.
Cadel
E
Fraczkiewicz
A
Menand
A