Extension of an anisotropic model of creep in single crystal superalloys to variable loading and multiaxial loading

An understanding of the mechanisms controlling the anisotropic deformation of single crystal superalloys is a prerequisite for establishing reliable constitutive laws for engineering design. It is clear that the anisotropy in creep strength cannot be explained in terms of Schmid law concepts and the operation of a single slip system. A model, that considers the simultaneous operation of two families of slip systems. (111¯)〈101〉 and (100)〈011〉, has been shown to describe well: (i) an extensive database of uniaxial creep curves in the temperature range 750 to 950°C, (ii) crystal rotations during creep deformation, (iii) specimen shape changes resulting from creep deformation. This paper will give an extension of the model to account for time dependent deformation in a range of more complex loading conditions.