Aluminum single crystals were cyclically deformed in single-slip at small strain amplitudes
at 77 K to presaturation. The observed mechanical behavior is consistent with other
recent work. The dislocation substructure was analyzed in detail. The structure can be
described as consisting of dense bundles or veins of dislocation dipoles, separated by
lower dislocation density regions where debris is evident. This debris was determined to
be principally relatively short dipole segments. Screw dislocations with the same Burgers
vector span the channels. Dislocations were essentially all of the same Burgers vector.
In-situ cyclic deformation experiments were successfully performed by the X-Y technique
where thin foils are stressed in alternating perpendicular directions. Screw dislocations
span the channel and easily move and reverse direction with shear reversal. Our
experiments indicate that loops frequently expand from the dipole bundles into the
channels and the edge component is absorbed by nearby bundles leaving screw segments
behind. Dipole "flipping" was not observed and these edges are relatively difficult to
mobilize. There is no obvious evidence for internal backstresses that assist plastic
deformation on reversal of the applied shear. / Graduation date: 1996
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34889 |
| Date | 20 September 1995 |
| Creators | Delos-Reyes, Michael A. |
| Contributors | Kassner, Michael E. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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