Coupled Analysis of Microstructure Evolution with Creep Deformation in Nickel-Based Superalloys by the Phase-Field Method

Directional coarsening of the gamma' phase (rafting) during creep in nickel-based superalloys was simulated by a phase-field model that calculates the evolution of both the (gamma + gamma') microstructure and the inelastic strain in the gamma phase. A two-dimensional simulation revealed that directional coarsening affected the macroscopic creep behavior and that the strain rate increased temporarily. The creep rate-time curve of the initial stage of transient creep was successfully reproduced by the simulation. Furthermore, the results of a three-dimensional simulation showed that the dislocations prefered the gamma phase perpendicular to the external tensile stress and demonstrated that the strain rate increased locally at the gamma/gamma' interface with a curvature when rafting occurs.