1981 Volume 22 Issue 10 Pages 723-732
Deformation behaviour of three kinds of isoaxial zinc bicrystals is described to make clear the effects of grain boundaries on plastic deformation. Secondary slip lines were observed near the grain boundary at an early stage of deformation in incompatible bicrystals, while they were not in compatible bicrystals. Most of secondary slip systems are activated to release the incompatibility developed in each crystal due to primary slips, and others are activated to cancel the bending moment which is caused by the shift of tensile axis due to primary slips.
0.1% proof stress increased with an increase in the degree of incompatibility. Difference in the proof stress, (τB-τS), between bicrystal and single crystal was related to incompatibility strain, Δε, by (τB-τS)∝\sqrt|Δε|. This relationship is in quantitative agreement with the theoretical one derived from Ashby’s theory, if an appropriate value is used for a constant which relates the dislocation density to the flow stress. It is concluded that the increase in 0.1% proof stress is caused by multiple slips near the grain boundary induced to release the incompatibility.