Deformation and fracture behavior of zircaloy-2 deformed at constant strain rate in iodine environment. I. Uniaxial tension test.:Uniaxial Tension Test

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The relation between strain rate and iodine stress corrosion cracking (SCC) was studied on Zircaloy-2 subjected to uniaxial stress under constant extension rate in an iodine partial pressure of 4 Torr and at a temperature of 350°C. The specimens were machined from actual fuel cladding tube. In iodine environment, the tangentially directed specimens registered sharp decreases in stress beyond maximum point ; this is attributed to crack initiation and propagation. Fracture ductility diminished with decreasing strain rate. Severe SCC was observed at strain rates below 2 × 10<SUP>-3</SUP> min<SUP>-1</SUP>. At high strain rates, the mechanism governing the rate of SCC appeared to be the time-dependent corrosion process. The axially directed specimens showed no signs of embrittlement due to gaseous iodine ; this is attributed to the particular texture of the Zircaloy. Fracture surface observations indicated that transgranular cleavage fracture along the basal plane appeared to play a significant role in the stages of SCC initiation and propagation.
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