MICROSTRUCTURE EVOLUTION AND FEM ANALYSIS OF [111] ORIENTED SINGLE CRYSTAL OF A NICKEL-BASED SUPERALLOY DURING TENSILE CREEP

The distribution of von Mises stress and strain energy density in regions near interfaces of gamma/gamma' phases was calculated by an elastic-plastic stress-strain finite element method (FEM), and the influences of applied stress on the von Mises stress distribution and coarsening regularity of gamma' phase in a [111] oriented single crystal nickel-based superalloy were also investigated. The results show that, after heat treated, the microstructure of the [111] oriented single crystal superalloy consists of a cubical gamma' phase embedded coherently in gamma matrix, and the cubical gamma' phase is regularly arranged along < 100 > direction. When tensile stress is applied along [111] direction, compared to (010)(gamma') plane, larger expanding lattice strain occurs on (100)(gamma') and (001)(gamma') planes under the action of principal stress component, which may trap Al, Ti atoms with bigger radius to promote gamma' phase directionally growing along [010] and [100] orientations on (010) plane, this is thought to be the main reason of gamma' phase grown directionally into a mesh-like rafted structure along (010) plane.