Finite-element modelling of anisotropic single-crystal superalloy creep deformation based on dislocation densities of individual slip systems

A finite-element model is proposed which describes the creep behaviour of a two-phase single-crystal superalloy. For the matrix phase, a user-defined material model is used. It describes the creep behaviour based on evolution equations for dislocation densities on individual slip systems. An interaction matrix determines the influence of one glide system on the other. Due to the face-centred cubic (fcc) symmetry, 9 independent parameters of the interaction matrix can be distinguished, describing slip on octahedral and cube glide planes with a Burgers vector of the type a/2<110>. The finite-element method (FEM) was used to describe the stress-strain behaviour as well as the dislocation evolution in matrix channels during creep deformation. Uniaxial stress in <100>, <110>, and < 111 > directions was considered. The evolution of the calculated dislocation densities and the resulting creep curve are compared with experimental observations.