High‐density specimens were plastically deformed under four‐point transverse bending. Tests were conducted in vacuum in the region 1400° to 1700°C under stresses of 1000 to 4500 psi. The activation energy for creep was 99.0 kcal/mole. Creep rate was directly proportional to the applied stress and inversely proportional to the square of the grain diameter. The deformation behavior is ascribed to a Nabarro‐Herring type mechanism. Results show that creep was the same in tension and compression.

Compressive creep of polycrystalline beryllium oxide was studied in the temperature range 2500" to 2800'F.The apparent activation energy for creep was 96.0 kcal per mole and the creep rate was linearly dependent on the applied stress. Results were consistent with the Nabarro-Herring creep mechanism. Experimental evidence showed that extrapolation of data to 320OOF was possible.

An etching solution is reported which can successfully reveal dislocation sites on the basal, first-and second-order prismatic, and the first-order pyramidal planes of beryllium oxide single crystals. Each of these crystallographic surfaces has an uniquely shaped dislocation etch pit which had not previously been reported. Freshly introduced dislocations on all the above planes were mobile at room temperature under high stresses. Dislocation motion was observed in several directions having low indices. The etchant also revealed dislocation sites in as-sintered and plastically deformed polycrystalline specimens.

This is ail informal report intended primarily for internal or limited external distribution. The opinions and conclusions stated are those of the author and may or may not be those of the laboratory.

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