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 gamma and gamma' phases in a high strength nickel base superalloy. Samples of Rene88DT were solutionised at 1150 degrees C and cooled under three different rates to provide fine and coarse gamma' size distributions. Samples were aged at 760 degrees C to precipitate tertiary gamma' 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.