Effects of temperature, strain rate, and specimen orientation on localized plastic deformation of irradiated zircaloy-2.

Both transverse and longitudinal Zircaloy-2 specimens irradiated up to 1.2 × 1020 n/cm2 (E> 1 MeV) were tested in tension with strain rates ranging 1.1 × 10-4~1.1 × 10-2 s-1 in the temperature range 200~400°C. Detailed observations of the specimen wall surface and microstructure were also made on samples deformed to various amounts of plastic strain, with a projector and an optical microscope. It was found that localized plastic deformation bands occurred in the temperature range approximately 280~330°C during straining to the ultimate tensile stress. Results also showed that the strain rate dependence of tensile properties, particularly the strain to the ultimate tensile stress, was associated with changes in the number and width of the localized deformation band with strain rates at a temperature of 300°C at which localized bands occurred. From a break of the straight line tracing the true stress-true plastic strain relationship, it was established that the onset stress and strain of the localized defor...