Two-dimensional X-ray diffraction to investigate γ/γ′ lattice misfits in different preparations of single-crystal nickel-based superalloy DD483

This paper investigates lattice misfits of γ/γ’ phases in different preparations of a single-crystal nickel-based superalloy DD483 using the two-dimensional X-ray diffraction with the positive and reciprocal space mapping. The lattice misfit in a heat-treated sample has a positive value, in contrast to the negative value lattice misfit in an as-solidified sample. This difference is due to the alloying-element diffusion decreasing the lattice constant of the γ phase and increasing that of the γ′ phase during heat treatment. The lattice constants of the γ and γ′ phases in a creepdeformed sample are lower than those in the heat-treated state, respectively. The difference in the lattice constants of the γ′ phase in heat-treated and creep-deformed samples is less than that of the γ phase, so the lattice misfit in the creep-deformed sample slightly increases. This trend is due to the superposition of coherent stress, internal stress, and applied stress. Ultimately, we show that the method measures the lattice constants and misfits of the γ/γ’ phases in nickel-based superalloys simply, conveniently, and precisely. © 2015 by Begell House, Inc.