The effect of elevated deformation temperatures on microstructural parameters in fatigued nickel single crystals has been studied by transmission electron microscopy. The height and length of edge dipoles and the mean dislocation density in the matrix bundles have been measured as functions of temperature using weak-beam contrast. It was found that the mean height of edge dipoles increases from 3 .9 nm at room temperature to 6.2 nm at 750 K, whereas the dislocation density decreases with increasing temperature. This shows that the structure lengths on a microscopic scale are enlarged, which is the same tendency as that observed at a mesoscopic structure level.
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