The strain-aging behavior of annealed Zircaloy-2 in vacuum was studied as a function of deformation temperature, integrated fast-neutron dose, and degree of cold work. Strain aging occurred in the temperature range 200 to 500 C. Transmission electron microscopy showed that in the temperature range 300 to 450 C, dislocations were arranged in a cell structure, and that at 500 C two-dimensional hexagonal dislocation nets were present. Between 200 and 400 C, the strain aging was found to be due to the presence of oxygen; however, the origin of the strain aging between 400 and 500 C was not identified. At 300 C the strain aging decreased with increasing neutron dose and decreasing amounts of prior cold work. Post-irradiation annealing experiments between 400 and 600 C increased the yield stress of the material at 300 C after irradiation at 325 C.

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