The probability of fatigue cracking along various types of grain boundary and persistent slip band was considered with regard to data on the cyclic deformation of bicrystals and columnar crystals. It was found that, in bicrystals, fatigue cracks always nucleated and propagated along high-angle grain boundaries; regardless of whether the grain boundary was perpendicular to, parallel to, or inclined to the stress axis. On the other hand, in the case of columnar crystals which contained low-angle grain boundaries, persistent slip-band/matrix interfaces became preferential sites for the initiation of fatigue cracks. Fatigue cracking along low-angle grain boundaries was never observed. In the case of a special [¯134]/[18 ¯¯2 7] bicrystal, with a Σ = 19b grain boundary and a common primary slip plane, grain boundary cracking also resulted in fatigue failure. It was suggested that the probability of fatigue cracking in fatigued Cu crystals increased in the order: low-angle grain boundaries, persistent slip bands, high-angle grain boundaries.

Relationship between the Fatigue Cracking Probability and the Grain-Boundary Category. Z.F.Zhang, Z.G.Wang: Philosophical Magazine Letters, 2000, 80[7], 483-8