To investigate the effect of atmospheric-corrosion on the early stage fatigue cracks, fatigue tests were made in air and in vacuum (3×10-3mmHg) on α-brass under push-pull loading, and both external and fractured surfaces were observed by means of optical and scanning electron microscopy.
It was found that fatigue lives, compared with the case iron, were much longer in vacuum than in air, and the improvement in life increased as the stress amplitude was reduced. The number of cycles up to fatigue crack nucleation in vacuum was found to be about 44 times longer than that in air. Crack nucleation in vacuum occurred predominantly along the slip bands. The number of intercrystalline fracture surfaces increased as crack length and stress amplitude increased. The morphology of transcrystalline fracture surfaces in vacuum was similar to that in air. On the other hand, in vacuum, intercrystalline fracture surface was not observed within the interior of the specimen and few near the specimen surface. Striations observed in vacuum were not clear.
