c © 2002 Kluwer Academic Publishers. Manufactured in The Netherlands. Nanoscale Studies of the Chemistry of a Rene ́ N6 Superalloy

Abstract. Atom-probe field-ion microscopy (APFIM) is used to study partitioning of the alloying elements between the γ (FCC) and γ ′ (L12) phases and their segregation behavior at γ /γ ′ interfaces of a Rene ́ N6 nickel-based superalloy. The atomic-scale resolution and real space reconstruction capability for elemental chemical mapping makes three-dimensional atom-probe microscopy especially suitable for subnanoscale investigations of complex multicomponent superalloys. Concentration profiles of this alloy, obtained from an atom probe analysis, reveal the partitioning behavior of the alloying elements in Rene ́ N6. As anticipated, the matrix strengtheners, such as Mo and W, are partitioned to the γ (FCC) matrix, while Re segregates at the γ /γ ′ interfaces; the Gibbsian interfacial excess of Re is determined by both one-dimensional (2.32 atoms nm−2) and three-dimensional atom-probe microscopies (3.92 atoms nm−2) and the values obtained are in reasonable agreement