Fatigue appearance transgranular

Fig. 1.48 Different appearance of a fatigue crack a transgranular, b intergranular...

Fig. 2.39 Transgranular brittle striations by corrosion fatigue on admiralty alloy in water diluted ammonia (reproduced with permission of [41]). Four concentrically circles appear intersecting the continuous array of cleavage steps. Black arrows indicate propagation direction...

Basically, there are 4 modes through which corrosion appears on materials surface, as shown schematically in Fig. 16.26. Generalized corrosion acts on the entire surface exposed to the environment (rust for example) and is not treated in this book. Pitting and SCC have been considered in Chaps. 14 and 15. SCC can be either intergranular or transgranular. Fatigue is always transgranular unless it is... 

The fracture morphology is transgranular with ductile striations of the type seen in Fig. 16.27. The second case (B) of Fig. 16.32 is that in which the Kj cc of the material is lower than the threshold AKi,h for fatigue therefore SCC will appear first, unless the frequency / of load cycles is too large (f 1 cpm). The case is that interesting the crosshatched zone of Fig. 16.31. Now, as discussed in Sect. 15.3, the FCGR, da/dN. 

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