Abstract
In order to study a more detailed mechanism of fatigue crack propagation, dislocation structures in the vicinity of fatigue cracks of thin-foil α-brass, copper and aluminium have been observed by transmission electron microscopy.
It has been found that well-developed substructures are formed in the vicinity of fatigue cracks, subgrain sizes of α-brass, copper and aluminium are 2∼3 μ, 1∼2 μ and 2∼4 μ, respectively, and more distinct substructures are formed in order of the stacking fault energies. Moreover, direct evidence, which suggest that fatigue cracks might propagate through sub-boundaries, is obtained on aluminium.
In conclusion, the results of electron microscopic observations are in good agreement with those of X-ray examination which have been reported in the previous paper, suggesting that substructure formation plays an important role in the propagation of fatigue cracks.
