Non-destructive characterization of the spatial variation of / lattice misfit in a single-crystal Ni-based superalloy by energy-resolved neutron imaging

Malamud, F.*; Santisteban, J. R.*; Gao, Y.*; Shinohara, Takenao   ; Oikawa, Kenichi   ; Tremsin, A.*

Lattice misfit in nickel-based superalloys is one of the important microstructural parameters that control their mechanical properties, such as creep behaviour at high temperatures. Here, energy-resolved neutron imaging experiments are performed at a spallation neutron source to determine the spatial variation of lattice misfit on a second-generation nickel-based single-crystal superalloy specimen produced from a failed low-cycle fatigue specimen. An analysis of the position and width of those Laue peaks in the obtained transmission spectra allows determination of the lattice parameters of the and phases that compose the specimen, as well as the strain misfit and the misorientation between them. An analytical model is developed to describe the full wavelength pattern of Laue peaks arising from a specimen composed of two single crystals, and this model is used to perform least-squares refinements of the spectra measured at different positions of the specimen.