Fatigue crack growth resistant microstructures in polycrystalline Ni-base superalloys for aeroengines

Fatigue in the polycrystalline Ni-base superalloys is discussed, with particular emphasis on modelling the mechanism at the grain and sub-grain scale. The importance of Ni-base superalloys as aeroengine materials is summarised, and indications are given as to where modelling offers potential for further advancements. In the experimental section, there are three parts. The first identifies how at the microstructural scale, the instantaneous rate of fatigue crack growth is governed by the crack path selection mechanism. The second part describes a statistical analysis of i) crack arrests, ii) instantaneous crack growth rates and iii) and their dependence on linear elastic fracture mechanics parameters. It is shown that all fatigue crack growth events occurring at the microstructural scale can be represented by a few statistical distributions. Thirdly, an initial analysis of the underlying slip band and dislocation mechanism of conventional fatigue in Ni-base superalloys is presented.

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