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Rolling can result in anisotropy in the microstructure and mechanical properties of the sheet material. This study focuses on the very high cycle fatigue (VHCF) performance of magnesium alloys in the rolling direction (RD), normal direction (ND), and the bisecting angle between the ND and RD (ND–RD). The findings reveal that RD specimens demonstrate superior fatigue performance, while the ND specimens exhibit the lowest fatigue resistance. During the crack initiation stage, the primary influential factor is the maximum shear stress. Due to c‐axis alignment with ND direction in grains, the deformation mode for ND and RD specimens primarily involves first‐order pyramidal slip, while ND–RD specimens primarily undergo basal slip and prismatic slip. In early stable crack propagation, grain size and texture cause variations in the morphology of the rough area among the three directional specimens. Notably, the RD specimens show faster crack propagation during crack initiation than early stable propagation stage. Highlights: The rolled Mg alloys have the highest very high cycle fatigue strength along rolling direction.Texture and grain boundaries significantly affect crack initiation and early propagation.Maximum shear stress dominates slip‐induced crack initiation within primary grains. [ABSTRACT FROM AUTHOR]

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. Highlights: 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. [ABSTRACT FROM AUTHOR]

During steam turbine rotor operation, the startup and showdown processes can cause asymmetric loading stress, leading to fatigue damage. To research the cyclic deformation behavior and fatigue failure mechanisms of 9% Cr‐based steel under asymmetric loading conditions, the strain ratios including −1, 0, and 0.1 are introduced into the low cyclic fatigue tests at 430°C. The results show the cyclic softening behavior is observed under three strain ratios at 430°C. As the strain ratio increases, the crack initiation sources, plastic strain, and consumed energy present an increasing trend. Comparing the microstructure morphology at different strain ratios, the coarsening lath and carbides affect fatigue crack initiation. Besides, the grain rotation and dynamic recrystallization can be observed, resulting in the cyclic softening behavior during the fatigue test. Finally, a new fatigue life prediction model is proposed at 430°C. Highlights: The low cycle fatigue tests are conducted under R = −1, 0, and 0.1 at 430°C.The dynamic recrystallization is observed, resulting in the cyclic softening behavior.A fatigue life prediction model considering the strain ratio is proposed at 430°C. [ABSTRACT FROM AUTHOR]

The present study envisaged the behavior and relevant crack initiation mechanism of super martensitic stainless steel (0Cr13Ni5Mo) at elevated temperature (ET) under very‐high‐cycle fatigue (VHCF). Fractographic analysis revealed that all the VHCF cracks of the failure specimens initiated from the surface and formed fine granular area (FGA) morphology at ET in an absence of vacuum. The initiation characteristic area (ICA) consisted of an initiation site, a relatively smooth area, and the annular continuous FGA. FGA was formed in the peaks and valleys of local microstructures, and the smooth regions connected these peaks and valleys dominated by shear stress. It was observed that the FGA was unevenly distributed on the crack surface related to the local microstructure and below the grain surface relevant to local strain distribution. The stress intensity factor (SIF) and the crack tip plastic zone of the ICA slightly changed with temperature. Highlights: The vacuum environment was no longer necessary for the formation of FGA.FGA was unevenly distributed related to local microstructure and local strain condition.The fatigue cracks' initiation and early propagation were affected by local microstructure. [ABSTRACT FROM AUTHOR]

Ultralight Mg–Li alloys are promising aerospace materials as they are the lightest structural alloys at present; however, their fatigue behaviors remain to be explored. This work focuses on the fatigue strength and crack initiation behavior of an extruded dual‐phase Mg–Li alloy (LZ91) under high‐cycle and very‐high‐cycle fatigue regimes. The fatigue limit of LZ91 alloy at 109 cycles was determined to be 78 MPa, and the fatigue ratio is 0.46. Microstructural characterization demonstrates that fatigue cracks tend to initiate at β‐Li phase‐enriched regions. The α‐Mg phase presents a < 101¯0> fiber texture with a basal plane that has low deformation in the extrusion direction and acts as an enhanced phase in relation to the β‐Li phase. Deformation discrepancies cause localized cyclic plasticity at the Li phase that leads to fatigue crack initiation. Highlights: The influence of local microstructure on the fatigue behavior was studied.Fatigue strength of LZ91 is 78 MPa at 109 cycles, and the fatigue ratio is 0.46.The α‐Mg phase exhibits strong textures and acts as an enhancing phase in the material.The local proportion of α‐Mg phase significantly affects the crack initiation behavior. [ABSTRACT FROM AUTHOR]