Calculation of the internal stresses and strains in the microstructure of a single crystal nickel-base superalloy during creep

Abstract The evolution of internal stresses and strains in the microstructure of a single crystal nickel-base alloy during annealing and during creep in [001] direction has been calculated using a visco-plastic model. Two limiting conditions are considered: an “overloading” case where the internal stresses reach the critical resolved shear stress of the whole γ′ volume and an “underloading” case where the critical resolved shear stress of the γ′ precipitate is reached only at distinct areas. During creep deformation a triaxial stress state evolves in the microstructure and large pressure gradients are built up. The influence of an initial coherency misfit is shown to be negligible after short times of creep. The calculations allow the prediction of flow patterns in the microstructure, creep-induced lattice parameter changes, type and arrangement of interfacial dislocations and of the dependence of the stationary strain rate on the cube or plate morphology of the γ′ phase.

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