Uncertainty in the determination of fatigue crack facet crystallography

Effect of Frequency, Environment, and Temperature on Fatigue Behavior of E319 Cast-Aluminum Alloy: Small-Crack Propagation

“…In all cases, the fracture surfaces are generally normal to the loading direction. The features typical of transgranular crack growth that were reported for some aluminum alloys [25] were not observed. This is consistent with the observations that fatigue-crack growth in overaged aluminum alloys favors a wavy slip mode and exhibits conventional stage II propagation.…”

“…Similar dependence of crack-growth rate on water exposure was observed for a 7075-T651 aluminum alloy [15] and some Al-Cu-Mg/Li alloys. [25] The calculated water exposure in each environmental condition is summarized in Table II. Here, the water partial pressure, P, was calculated as follows:…”

“…The subtle change of fracturesurface morphology with water exposures indicates that, although the fatigue-propagation behavior is influenced by water exposure, the response of fatigue-crack growth rate to the water exposure for the investigated E319-T7 cast-aluminum alloy is not as significant as for those aluminum alloys, which exhibited obvious morphology change of fracture surface in different environments. [25] B. Effect of Frequency and Temperature on Fatigue-Crack Propagation at 250°C Figure 9 presents the fatigue-crack propagation at 20°C and 250°C, at a frequency of 20 kHz.…”

Environmental Fatigue-Crack Surface Crystallography for Al-Zn-Cu-Mg-Mn/Zr

“…Techniques include X-ray Laue back reflection, [18][19][20][21][22][23][24] etch-pit shape, [6,[13][14][15][25][26][27][28] selected area electron diffraction in the transmission electron microscope (TEM), [25,29] stereology [9] combined with diffraction techniques including X-ray diffraction, [30] and electron backscattered diffraction (EBSD). [8,9,17,31] The majority of these methods are semiquantitative, restricted to large grain-size model microstructures or limited to very small areas and sparse results. Scanning electron microscope (SEM)-based stereology combined with EBSD was employed in the present study to best probe micron-scale features that are relevant to technologically important alloy systems.…”

Crystallography of Fatigue Crack Initiation and Growth in Fully Lamellar Ti-6Al-4V

“…THE union of electron backscatter diffraction (EBSD) and quantitative tilt fractography [1][2][3] has provided an efficient method for relating crystallographic information obtained directly from a fracture surface (or a polished face that intersects it) to the spatial orientation of features on it. The direct method, in which EBSD patterns are collected directly from the as-fractured surface without additional preparation, has been reported to have an accuracy between 1 [3] and 3 deg [4] when the spatial information and crystallographic information are obtained in the same microscope session without rotating the stage. This method is limited, however, by the necessity for a relatively flat fractured surface that was not accompanied by substantial plasticity during fracture.…”