Microstructure Evolution and Analysis of A [011] Orientation, Single-Crystal, Nickel-Based Superalloy During Tensile Creep

By means of the elastic-plastic finite-element method (FEM) for calculating the distribution features of the von Mises stress and strain energy density, the influences of the applied stress on the von Mises stress of the gamma'/gamma phases and the rafting of the gamma' phase for the [011] orientation, single-crystal, nickel-based superalloy are investigated. The results show that, after being fully heat treated, the microstructure of the [011] orientation, single-crystal, nickel-based superalloy consists of the cuboidal gamma' phase embedded coherently in the gamma matrix, and the cuboidal gamma' phase on (100) plane is regularly arranged along a 45 deg angle relative to the [011] orientation. Compared with the matrix channel of [010] orientation, the bigger von Mises stress is produced within the [001] matrix channel when the tensile stress is applied along the [011] orientation. Under the action of the larger principal stress component, the bigger expanding lattice strain occurs on the (001) plane of the cuboidal gamma' phase along the [010] direction, which may trap the Al, Ti atoms with a bigger atomic radius for promoting the directional growth of the gamma' phase into the stripe-like rafted structure along the [001] orientation. The changes of the interatomic potential energy, misfit stress, and interfacial energy during the tensile creep are thought to be the driving forces of promoting the elements' diffusion and directional growth of the gamma' phase.