Strains and dislocation densities within a rafted superalloy: In situ investigation during mechanical testing at 1080°C

Abstract

During in situ investigation of the distribution of lattice parameters within a superalloy with a rafted microstructure by Three Crystal Diffractometry, both the γ and γ' peak positions and shapes are shown to change. While the peak positions can be used to measure the average stresses and strains within both phases, the changes in shape are related to these in the dislocation distribution within the material. It is shown that the density and order of the dislocation array at the γ/γ' interface and within the γ' phase give different contributions to the peak width, and that the widening of both peaks under high stresses is due to an increase of the dislocation density within the rafts.