Microtexture, asperities, and crack deflection in Al-Li 2090 T8E41

Jake D. Haase, Abbas Guvenilir, Jason R. Witt, Morten A. Langøy, Stuart R. Stock

Research output: Contribution to journalConference article

13 Scopus citations

Abstract

Roughness-induced closure is held to be responsible for very low fatigue crack growth rates observed in certain plate orientations of Al-Li 2090 T8E41, and the geometry of asperities producing this closure correlates with macrotexture. Little work. however, has focused on the role of individual grain orientations (microtexture) or of average orientation within small groups of adjacent grains (mesotexture) on the crack's path through a sample, i.e on whether the variation in grains' orientations determines where the crack will deflect. This paper reports synchrotron X-ray microbeam diffraction mapping of the three-dimensional microtexture in samples of Al-Li 2090. Groups of adjacent pancake-shaped grains are found to have very similar orientations, producing nearly single-crystal regions approaching thicknesses of 0.3 mm along the sample's S (short-transverse) direction. These near-single-crystal volumes produce large asperities with surfaces having substantial Mode III character, asperities which appear over the range of stress intensity ranges observed (approximately 5 to approximately 25 MPa√m). Results of these experiments suggest not only that this type of mesotexture plays an important role in determining fatigue crack path in compact tension samples of Al-Li 2090 but also that specific orientations of the groups of grains lead to large crack deflections.

Original languageEnglish (US)
Pages (from-to)160-173
Number of pages14
JournalASTM Special Technical Publication
Issue number1359
StatePublished - Jan 1 1999
EventProceedings of the 1998 Symposium on Mixed-Mode Crack Behavior - Atlanta, GA, USA
Duration: May 6 1998May 7 1998

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ASJC Scopus subject areas

  • Engineering(all)

Cite this

Haase, J. D., Guvenilir, A., Witt, J. R., Langøy, M. A., & Stock, S. R. (1999). Microtexture, asperities, and crack deflection in Al-Li 2090 T8E41. ASTM Special Technical Publication, (1359), 160-173.