In situ measurement of the lattice parameter mismatch of a nickel-base single-crystalline superalloy under variable stress

The evolution of the lattice parameters of the γ matrix and γ′ precipitates was measured in situ during high temperature tests of specimens with a raft microstructure at 1080 °C under variable load (0–300 MPa), done at the ESRF. Under low applied tensile stresses, the behavior of the specimens is purely elastic, while under stresses higher than the pre-strain stress plastic deformation takes place and results in changes of the effective lattice mismatch at the γ/γ′ interfaces. Modeling suggests a linear dependence of the lattice mismatch versus the applied stress, which is observed during the experiment.