X-ray Diffraction Investigations on Individual Grains in the Polycrystalline Ni-base Superalloy IN939 During Cyclice Loading I: X-ray Rocking Curve Broadening

Abstract

X-ray diffraction investigations were carried out to prove that X-ray methods can be applied for the assessment of fatigue-induced changes in the microstructure of Ni-base superalloys. Since the investigations were performed on single grains of a coarse grained alloy (IN 939), analysis of X-ray rocking curves can be applied. It was shown that the width of a rocking curve is sensitive to even small plastic deformations and that for the given experimental conditions the broadening can be taken as a measure for the accumulated plastic strain resulting from cyclic loading. The observed anisotropic behaviour of rocking curve broadening could be explained by the concept involving activation of selected slip systems