High‐Temperature Plastic Deformation of Polycrystalline Beryllium Oxide

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.