MODELING HIGH-TEMPERATURE CREEP OF ACADEMIC AND INDUSTRIAL MATERIALS USING THE COMPOSITE MODEL

The composite model of plastic deformation of materials developing a subgrain structure provides a framework for coupling the deformation of the soft subgrain interior and the hard subgrain boundaries through internal stresses. By specifying the kinetic laws for deformation of soft and hard regions according to the dominant dislocation obstacles, the model has been applied to three materials: pure aluminium, the Ni-based alloy NiCr22Co12Mo (Inconel 617) and the ferritic 12% Cr steel X 20 CrMoV 12 1. The formulation of the kinetic laws for the soft region was based on thermally activated glide through the dislocation structure in the case of aluminium and on solute and particle hardening in the case of the alloys. The kinetic laws for the hard region were similar in all cases, differing mainly in the amount of particle hardening. It is shown that the model is capable of modelling the transient creep of pure aluminium between two different steady states, accounting for strain hardening due to the formation of the subgrain structure during the primary creep of NiCr22Co12Mo and estimating the degree of softening which can be expected as a result of subgrain growth and particle coarsening during the long-term creep of the 12% Cr steel.