(a) (b)
Fig. 11. Longitudinal section of the specimen subjected to IPD-TMF cycling with mechanical strain amplitude 6×10−3 to fracture; (a) SEM image, (b) EBSD image.
Introduction of the tensile dwell to the loading cycle led also to the formation of the internal damage referred to as creep deterioration. Internal cracks developed during IPD-TMF cycling are documented on the longitudinal section of a specimen in Fig. 12. EBSD image in Fig. 12b reveals that the internal cracks follow the grain boundaries. The internal damage may significantly influence the growth of the dominant fatigue crack due to interaction of this crack with the internal cracks which were nucleated close to the crack tip. The joining of the dominant crack with internal cracks accelerates the crack growth.