Local chemical and structural gradients in the creep deformed superalloy SC16

Abstract

The local chemical concentrations of the elements in the nickel-base single crystal superalloy SC16 were examined by electron microscopy and atom probe tomography after standard heat treatment and creep deformation of 0.5% at 1223 K along the [0 0 1] direction. Creep deformation led to directional coarsening of the γ′ precipitates. The atom probe measurements were carried out along the [0 0 1] and [0 1 0] directions. Enrichment of Al and slight depletion of Ti in the γ′ precipitate near the γ′/γ interface were observed after creep deformation, whereas in the γ phase both these elements were depleted. An enrichment of Cr was detected near the interface in γ channels perpendicular to the applied stress. Small γ′ precipitates (size ∼3 nm) were observed by atom probe in the γ-matrix indicating non-equilibrium state of the alloy.