Interface coherency strain relaxation due to plastic deformation in single crystal Ni-base superalloys

The micromechanical behavior under compression for a cube-oriented single crystal Ni-base superalloy was in-situ studied by synchrotron high energy X-ray diffraction at room temperature. Both elastic and plastic deformation altered the mismatch strain between γ and γ′ phases with different variances. The deformation-induced interface coherency strain relaxation was observed after yielding as evidenced by an increment of lattice mismatch and an abnormal decrease in full width at half maximum (FWHM), which is attributed to aggregating of dislocations toward phase boundaries. A dislocation-mismatch model is proposed to correlate the relative change in lattice mismatch and FWHM during deformation, which fits the experiment well.