Fine Subgrain Structure Adjacent to Fatigue Cracks.
Technical rept. 1 Apr-15 Aug 71,
MIDWEST RESEARCH INST KANSAS CITY MO
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Deformation microstructures adjacent to fatigue cracks in 2024-T4 and 7075-T6 aluminum, and Ti -6Al -4V alloys have been examined by transmission electron microscopy. The data show that material within 1-2 micrometer of a tensile-mode crack consists of very fine 0.1 micrometer subgrains in all three materials. The average misorientation between the subgrains is 2-4 degrees. The presence of this substructure, which seems to be independent of initial metallurgical condition, is used to explain the weak dependence of Stage 2 crack growth rates on the initial condition in high stacking fault energy materials. No evidence of precipitate reversion was observed adjacent to the fatigue cracks in 7075-T6 aluminum. Author
- Metallurgy and Metallography