Microstructure evolution and FEM analysis of a [011] oriented single crystal nickel-based superalloy during compressive creep

By means of the stress-strain finite element method (FEM) in elastic-plastic regime, the influences of the applied stress on the distribution of von Mises stress and evolution of shape regularity of gamma' phase in a [0 1 1] oriented single crystal nickel-based superalloy are investigated. Results show that, after full heat treatment, the microstructure of [0 1 1] oriented single crystal superalloy consists of the cuboidal gamma' phase embedded coherently in the gamma matrix phase, and on (1 0 0) plane aligned regularly at angle of 45 degrees relative to the [0 1 1] orientation. During compressive creep, the cuboidal gamma' phase is transformed into the mesh-like lamellar rafted structure on (100) plane. Therefore, the changes of the lattice strain, the strain energy density and interfacial energy are thought to be the driving forces of the element diffusion and gamma' phase directional growth. During compressive creep, the lattice contraction occurs on (1 0 0) plane of the cuboidal gamma' phase along [0 0 1] and [0 1 0] directions, whose extruding effect may repel Al, Ti atoms with bigger radius. Therefore, the expanding strain of lattices along [1 0 0] direction on (0 1 0) and (0 0 1) planes of the cuboidal gamma' phase may trap Al, Ti atoms to promote the directional growth of gamma' phase on (1 0 0) plane along [0 0 1] and [0 1 0] directions, which is thought to be the main reason for the gamma' phase growing directionally into the mesh-like lamellar structure. (C) 2013 Elsevier B.V. All rights reserved.