INFLUENCE OF TEMPERATURE ON MICROSTRUCTURAL PARAMETERS OF CYCLICALLY DEFORMED NICKEL SINGLE-CRYSTALS

The effect of elevated deformation temperatures on microstructural par ameters in fatigued nickel single crystals has been studied by transmi ssion electron microscopy. The height and length of edge dipoles and t he mean dislocation density in the matrix bundles have been measured a s functions of temperature using weak-beam contrast. It was found that the mean height of edge dipoles increases from 3.9 nm at room tempera ture to 6.2 nm at 750 K, whereas the dislocation density decreases wit h increasing temperature. This shows that the structure lengths on a m icroscopic scale are enlarged, which is the same tendency as that obse rved at a mesoscopic structure level.