Experimental observations of void growth in the Zr-2.5Nb pressure tube alloy

Voiding during tensile loading of Zr-2.5Nb pressure tube alloy has been experimentally observed at two temperatures. Tensile specimens cut from the wall of a pre-service pressure tube were tested to various degrees of strain and then sectioned to allow internal voids to be examined. A point counting procedure was used to determine the void volume fraction at various levels of strain. Scanning electron microscopy was completed to determine the degree of voiding, the number and size of voids and the void morphology. Observed voids generally remain small while the overall void fraction increased with increased strain. This suggests that the void formation process in this material is dominated by extensive void nucleation, with little growth of the nucleated voids before void coalescence and final fracture.