Effect of hydride morphology on the failure strain of pre-cracked Zircaloy-4 cladding under biaxial stress conditions

Li, F.  

Li, F.

The effect of hydride morphology on the failure behavior of cladding tube was investigated using biaxial-EDC testing method. Cold-worked, stress-relieved and recrystallized Zircaloy-4 tubes with pre-crack were used as test specimens. The specimens were pre-hydrided. A decrease in the failure strain (hoop strain at failure) with increasing hydrogen content was observed at stress-relieved samples. The failure strain of the sample was more sensitive to hydrogen content under higher strain ratio. Micro-crack formation in hydrides is considered to be the microscopic failure mechanism of the decrease in failure strain. A decrease in the failure strain with increasing hydrogen content was observed similarly at cold-worked samples. No significant decrease in failure strain with increasing hydrogen content (up to about 280 ppm) was observed at recrystallized samples. This is probably because the enhanced ductility of recrystallized samples suppressed the effect of micro-cracks formed in hydrides on the decrease in failure strain.