A study of the effects of particle 3-dimensional geometry and micro-texture on fatigue crack initiation behaviors in an Al–Cu alloy using focused ion beam and electron backscatter diffraction

An experimental methodology for quantitative characterization of multi‐site fatigue crack nucleation in high‐strength Al alloys

“…The reason why Fe‐containing particles become the preferred crack initiation sites is likely to be associated with their brittleness, as revealed by the measurements of hardness and elastic modulus using nano‐indentation in the Al alloys . The sizes of the particles that lead to fatigue damage range from 2.3 to 200 µm in diameter, indicating that fatigue cracks are not necessarily nucleated at larger particles on the surface of the alloys It has recently been demonstrated by the authors of the present paper that the particle thickness is the key factor controlling the driving force for the growth of micro‐cracks in the prior‐fractured particles, as revealed by micro‐sectioning the fractured particles using FIB (focused ion beam) . It has also been found that Fe‐containing particles are responsible for fatigue crack initiation on L‐T and L‐S planes, but Si‐bearing particles could only become the predominant crack nucleation sites on the T‐S plane in AA7075 T651 Al alloys .…”

“…The reason why moisture promoted fatigue crack initiation at particles in the AA2026 T3511 alloy was likely to be attributed to that water molecules might reduce the resistance to micro‐crack growth at the tips of the micro‐cracks in the prior‐fractured particles at which cracks were predominantly initiated in the alloy (Fig. a), similar as in AA2024 and AA7075 Al alloys . As a result, those prior‐fractured particles that could not lead to fatigue crack initiation at a cyclic stress in dry air could do so at a higher RH but the same stress level in the alloy, thereby more FWLs could occur at 50% RH than at 0% RH, as shown in Figs and .…”

“…As AA2026 aluminium alloys are a modified version of high purity AA2024 alloys, the preferred fatigue crack initiation sites in the alloys are same as those (i.e. Fe‐containing particles Al 7 Cu 2 Fe) found in the AA2024 alloys, although the particle number density in AA2026 alloys is much lower than in the AA2024 alloys . It has been recognized that moisture in ambient air could compromise the high cyclic fatigue properties, especially crack initiation behaviour from constituent particles, in the Al alloys, because of hydrogen embrittlement caused by water moisture reacting with Al .…”

Textures and microstructures of AA3xxx hotbands from two different continuous casting processes

“…[1][2][3] In hot rolling or hot pellets compact, major process parameters, i.e. temperature, strain, strain rate and inter-pass holding time, strongly influence microstructure and texture evolution.…”

“…The thermo-mechanical processing, involving a combination of deformation and recrystallisation during hot rolling or hot pellet compacting, has obviously important effect on the formations of microstructures and textures in many aluminium alloys, which are critical in affecting the mechanical and fatigue properties of final sheet product of the alloys. [1][2][3] In hot rolling or hot pellets compact, major process parameters, i.e. temperature, strain, strain rate and inter-pass holding time, strongly influence microstructure and texture evolution.…”