Reorientation of Hydrides and Its Effect on the Mechanical Properties of Zr-Nb-Sn-Fe Cladding Tubes

Abstract

The reorientation of hydrides and its effect on the fracture of Zr-Nb-Sn-Fe cladding tubes were investigated. The reorientation of hydrides along the radial direction was most pronounced if the tube was cooled from 573 to 473 K under circumferential loading. Reorientation occurred much less frequently at either higher (from 673 to 573 K) or lower (from 473 to 373 K) temperature range. The strength decreased to 250 MPa and the ductility decreased to zero in the tube which was reorientation-treated from 573 to 473 K (RS32AC). Fracture surface of RS32AC sample exhibited flat cleavage fracture along the radial hydride platelet. The reorientation of hydrides was also found to increase with increase of loading time, suggesting time dependent stress-aided dissolution of circumferential hydrides and reprecipitation of radial hydrides.