Stress-induced reorientation of hydrides and mechanical properties of Zircaloy-4 cladding tubes

Stress-induced reorientation of hydrides and its effect on the stress-strain response of Zircaloy-4 cladding tubes were investigated. The reorientation of hydrides along the radial direction was most pronounced if the tube was cooled from 300 to 200 °C under circumferential loading. Reorientation occurred much less frequently at either higher (cooled from 400 to 300 °C) or lower (cooled from 200 to 100 °C) temperature range. The population of radial hydrides in R43H7 (which was cooled from 400 to 300 °C and maintained at 300 °C for 7 h) increased drastically during annealing at 300 °C, suggesting time dependent stress-aided dissolution of circumferential hydrides and reprecipitation of radial hydrides. The drastic decrease of the strength and the complete loss of the ductility were observed in R32AC and R43H7.