Application of X-ray and neutron diffraction to determine lattice parameters and precipitate volume fractions in low misfit nickel base superalloys

Synchrotron X-ray diffraction and neutron diffraction techniques are employed to characterise the lattice parameters and volume fraction of γ and γ′ phases in a high strength nickel base superalloy. Samples of Rene88DT were solutionised at 1150°C and cooled under three different rates to provide fine and coarse γ′ size distributions. Samples were aged at 760°C to precipitate tertiary γ′ and coarsen secondary precipitates. Lattice parameter misfit and coefficient of thermal expansion parameters were also determined. Results indicate significant microstructure changes within the samples during the initial 25 h of aging.