Abstract
The effects of slip character and grain size on the intrinsic material and extrinsic closure contributions to fatigue crack growth resistance have been studied for a 7475 aluminum alloy. The alloy was tested in the underaged and overaged conditions with grain sizes of 18 μm and 80 μm. The fracture surface exhibited increased irregularity and planar facet formation with increased grain size, underaging, and tests in vacuum. These changes were accompanied by an increased resistance to fatigue crack growth. In air the 18 μm grain size overaged material exhibited relatively poor resistance to fatigue crack growth compared with other microstructural variants, and this was associated with a lower stress intensity for closure. All materials exhibited a marked improvement in fatigue crack growth resistance when tested in vacuum, with the most significant difference being ˜1000× at a ΔK of 10 MPa m1/2 for the 80 μm grain size underaged alloy. This improvement could not be accounted for by either an increase in closure or increased crack deflection and is most likely due to increased slip reversibility in the vacuum environment. The intrinsic resistance of the alloy to fatigue crack growth was microstructurally dependent in vacuum, with large grains and planar slip providing the better fatigue performance.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
