Abstract
Equilibrium Re segregation is studied at a grain boundary in a single-phase W–25-at. %-Re alloy employing atom-probe field-ion microscopy. The grain-boundary concentration is measured, without data deconvolution, to be 73.8±5.45 at. % Re at an interface plane. This is the first direct proof that segregation at a grain boundary can be purely two dimensional, and that it can occur at a so-called low-energy interface.