Large-scale three-dimensional phase field simulation of γ ′-rafting and creep deformation

Abstract

Three-dimensional phase field simulations of coupled γ/γ ′ microstructural evolution and plastic deformation in single crystal Ni-Al are carried out at micrometer scales. Coherent γ/γ ′ microstructures and plastic deformation in γ-channels are described using a single, consistent methodology based on Khachaturyan's phase field microelasticity approach to coherent precipitates and dislocations. In particular, a new set of phase fields is introduced to characterize local density of dislocations from individual active slip systems. To increase the length scale of the phase field simulations, the Kim–Kim–Suzuki (KKS) treatment of γ/γ ′ interfaces was adopted. The rafting kinetics, precipitate-matrix inversion process and the corresponding creep deformation are characterized with respect to parameters such as applied stress and lattice misfit. The simulation results on γ ′-rafting kinetics and morphological evolution of the γ/γ ′ microstructures are compared with available experiment. The model can be used to carry out parametric studies of the effects of material and processing parameters such as alloy composition, external stress and working temperature on γ ′-rafting kinetics, morphological evolution and the corresponding creep deformation.

Keywords:

• plastic deformation
• dislocation
• microstructural evolution
• directional coarsening
• Ni-base superalloy

Acknowledgements

We gratefully acknowledge many helpful discussions with Professor T.M. Pollock at University of Michigan, Dr. M. Fährmann at Special Metals Corporation, Professor S.R. Kalidindi at Drexel University and Professor M. De Graef at Carnegie Mellon University. The work is supported by the US Air Force Office of Scientific Research through the MEANS2 program (Grant No. FA9550-05-1-0135) and the National Science Foundation (Grant No. 0606417) (YW). The simulations were performed on Sun Opteron cluster at the Arctic Region Supercomputing Center.