| Abstrakt: |
In order to improve our understanding of the link between the cyclic deformation of single crystals and of polycrystalline materials, a study was performed on copper bicrystals. Testing under strain control within the high cycle regime was performed in isoaxial [149] (90° and 180°) twist boundaries and [149]/[001] bicrystals, all with boundaries perpendicular to the tensile axis. A Grain Boundary Affected Zone (GBAZ), where multiple slip dominated, appeared when the boundaries developed compatibility stresses. Experiments showed that the behavior of macroscopically compatible bicrystals, 180° boundaries, is approximately similar to that of a monocrystal, whereas the fatigue responses of the other misorientation show a grain boundary effect, which increases the cyclic stress. The strain in each grain of the [149]/[001] sample was measured separately. The plastic deformation in the adjacent crystals oscillated during initial hardening; finally, the soft grain carried approximately five times the plastic strain of the other grain. © 1997 Acta Metallurgica Inc. |
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