Micro-, meso- and macro-texture and fatigue crack roughness in Al-Li 2090 T8E41
- Georgia Inst. of Tech., Atlanta, GA (United States)
The use of synchrotron polychromatic x-ray microbeams in the transmission geometry is described for mapping grain orientation as a function of position and for relating this microtexture to the formation of large asperities on fatigue crack surfaces in Al-Li 2090 T8E41. In common with the centers of rolled plates of many aluminum alloys, Al-Li 2090 T8E41 has a sharp average texture or macrotexture different from that in the outer portions of the plate. The geometry of large asperities in Al-Li 2090 has been related to this macrotexture, and the resulting roughness-induced crack closure is recognized to be responsible for the very low crack propagation rates in certain plate orientations. This report focuses on why asperities form at certain positions and why the crack remains relatively planar elsewhere. The microtexture (i.e., the grain-to-grain orientation variation) seems to be organized into a specific type of mesotexture: multiple adjacent grains have nearly identical orientations and form substantial volumes of near-single-crystal material. Transitions between differently oriented near-single-crystal volumes or between a near-single-crystal region and more randomly oriented grains appear to bound asperities.
- Sponsoring Organization:
- Office of Naval Research, Washington, DC (United States)
- OSTI ID:
- 302385
- Report Number(s):
- CONF-980405--
- Country of Publication:
- United States
- Language:
- English
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