Higher fatigue cracking resistance of twin boundaries than grain boundaries in Cu bicrystals

Two kinds of Cu bicrystals, with a high-energy grain boundary (GB) and a coherent twin boundary (TB) parallel to the loading direction respectively, were cyclically deformed to reveal the fatigue cracking mechanisms. It is shown that intergranular fatigue cracking occurred firstly in the bicrystal with the GB, while the persistent slip bands became the preferential cracking sites in the bicrystal with TB. These results indicate that the TB has an intrinsically higher fatigue cracking resistance than the GB.