In order to understand the basic mechanismof intergranular cracking in pure metals duringfatigue, stress-controlled push-pull fatiguetests were carried out with high purity aluminium.Tests were interrupted frequently so as to studythe grain boundary (GB) cracking behaviour bythe surface observation. The results show thatcrack initiation at GB was a process controlledby multi-factors, such as boundary structure,GB-slip interaction, GB sliding and so on. Ifthese factors are varied so that the incompati-bility at a GB increased, the possibility ofcyacking at the boundary will be raised. Someinteygranular cracking phenomena are not ableto be explained by the GB stepping mechanism.
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