Short fatigue crack path determinants in polycrystalline Ni-base superalloys

A. Boyd-Lee*, J.E. King

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review


    Fifty seven short fatigue cracks in the Ni-base superalloy AP1 have been examined, to ascertain how the paths taken by growing fatigue cracks are determined. The observations were made on the surface of a smooth specimen, and on the exposed fracture surfaces. Three dimensional reconstructions of the vulnerable microstructures in the vicinity of the cracks were produced. Initiation occurred in mode II, with the lines of intersection of the initiation sites with the specimen top surface orientated at approximately 45° to the tensile axis. These initiation sites developed in slip bands which crossed a large grain and at least one other grain via a grain boundary with a low angle of misorientation. 'River markings' on one of the initiation facets, indicated that the crack first opened from the top centre of the initiation grain. Subsequent to initiation, the growth paths of these cracks are related to the misorientations of the grains and the progress of the crack front.
    Original languageEnglish
    Pages (from-to)1-14
    Number of pages14
    JournalFatigue and Fracture of Engineering Materials and Structures
    Issue number1
    Publication statusPublished - Jan 1994


    • crystalline materials
    • fatigue of materials
    • fracture mechanics
    • grain boundaries
    • metallographic microstructure
    • nickel alloys
    • superalloys
    • surfaces
    • crack initiation
    • crack paths
    • fatigue cracks
    • nickel base superalloy AP1
    • slip bands
    • crack propagation


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