Evolution of the γ/γ′ interface width in a commercial nickel base superalloy studied by three-dimensional atom probe tomography

The compositional width of the γ/γ′ interface in a commercial nickel base superalloy has been determined using three-dimensional atom probe tomography. Initially, on formation during continuous cooling, the primary γ′ precipitates exhibit a sharp interface while the secondary γ′ precipitates exhibit a substantially diffuse interface. On subsequent isothermal aging, the interface width increases for the primary γ′ precipitates while it decreases for the secondary γ′ precipitates, reaching a near-equilibrium width for both types of interfaces after prolonged aging.