Twin boundary: Stronger or weaker interface to resist fatigue cracking?

The fatigue cracking mechanisms at twin boundaries (TBs) are investigated by considering the stacking fault energy, dislocation slip mode and the difference in the Schmid factors (DSF) between matrix and twin. In Cu and its alloys, the occurrence of TB cracking becomes much more frequent with either increasing the alloying component or the DSF. Considering the interactions between dislocations and TBs, a semiquantitative relationship based on the statistical experimental results is established to describe the TB cracking mechanism.