Figure 6: General fatigue cracking mechanisms of the twinned bicrystals with all possible TB inclinations (0° to 90°).
From: Controllable fatigue cracking mechanisms of copper bicrystals with a coherent twin boundary
The fatigue cracking behaviours are shown in the upper part of the figure and the schemes for the corresponding slip systems are displayed in the lower part. In regions I and V, S1 and S3 slip systems operate easily and there is good strain compatibility at the TB, therefore the fatigue cracks nucleate along the SBs first; in regions II–IV, the S2 slip systems operate easily and concentrate at the TB which leads to the preferential shear fatigue cracking at the TB.
