Effect of microstructure and local stress on small crack initiation and propagation paths in coarse-grained FeCrAl alloys

This study investigated the high cycle fatigue crack initiation and propagation behaviors in coarse-grained FeCrAl alloys, with a focus on the relationship between the path of small cracks and the local microstructure. The results show that the small cracks initiate along the {100} slip plane due to the synthetical influence of local microstructure and shear stress. The initiation zone forms inclined areas with layered fine-grain areas caused by cyclic shear stress. Quantitative analysis of the stress intensity factor (SIF) indicates that in the realm of mixed-mode loading, the SIF of Mode I takes the lead in determining the intensity of stress and strain fields at the crack tip. As the crack propagates further, the SIF steadily increases. Once it reaches a specific threshold, the propagation mode within a coarse grain shifts from Mode II to Mode I. Moreover, fatigue life increases with a tendency for decreased SIF during crack deflection. The influence of microstructure on crack initiation and early propagation behavior was studied.The cyclic shear stress leads to the formation of layered fine-grain areas.The quantitative analysis elucidates the reason for the deviation of crack direction within a coarse grain.

Automated summary

This study investigated the high cycle fatigue crack initiation and propagation behaviors in coarse-grained FeCrAl alloys, focusing on the relationship between small crack paths and local microstructure. The results indicate that small cracks initiate along the {100} slip plane due to the combined influence of local microstructure and shear stress. The study also reveals the dominant role of the stress intensity factor (SIF) in determining stress and strain fields at the crack tip, with increasing SIF as the crack propagates.