Temperature dependence of lattice mismatch and γ′ volume fraction of a fourth-generation monocrystalline nickel-based superalloy

The strain distribution in a new generation nickel-based single crystal superalloy has been determined in the temperature range 293 K-1598 K. Measurements have been performed using diffraction of high energy synchrotron radiation (150 keV, lambda = 0.008 nm) to determine the variations with temperature of the gamma/gamma' lattice mismatch and of the gamma' volume fraction. The chemical segregation at the dendrite scale and the internal stress induce a large range of values for the lattice mismatch. The measurements of the,gamma' volume fraction determined by X-ray diffraction are in agreement with those obtained by atom probe tomography, image analysis or computation.