An unusual deformation mode involving the formation of intrinsic stacking faults in the γ matrix of experimental Ru-containing γ–γ′ superalloys with high Co and Re contents was observed during high temperature creep (950C, 290MPa). The morphology, distribution and dependence of these stacking faults upon alloy chemistry was investigated along with their formation mechanism. Additions of Re and Co substantially decreased the stacking fault energy of the γ matrix. The observed stacking faults in the γ matrix form by the dissociation of a/2<110> matrix dislocations with Burgers vectors perpendicular to the loading direction in the early stages of creep. The dependence of creep properties upon elemental additions that influenced stacking-fault energy was considered.

Development of γ Phase Stacking Faults during High Temperature Creep of Ru-Containing Single Crystal Superalloys. S.Ma, L.Carroll, T.M.Pollock: Acta Materialia, 2007, 55[17], 5802-12