ASYMMETRIC CREEP DEFORMATION OF A SINGLE-CRYSTAL SUPERALLOY

The anisotropic creep behaviour of single crystal superalloys leads to changes in the orientation and shape of specimens of arbitrary initial orientations during high temperature deformation. A model of anisotropic creep has been applied to a creep database for the single crystal superalloy SRR99 tested in uniaxial tension on [001] and [111] orientations in order to evaluate the model parameters. These have been used to predict the changes in specimen cross-sectional shape resulting from creep deformation of more complex orientations. Experimental measurements have been made of the cross-sectional dimensions of initially cylindrical specimens as a function of local creep strain. The agreement between experimental measurement and model prediction is normally very good. The biggest disagreement, for the [211] specimen, indicates that macroscopic cube slip is dominant rather than mixed cube and octahedral deformation as indicated by the model.