Influence of locally concentrated hydrides on ductility of Zircaloy 4

Laboratory experiments were performed to investigate the influence of locally concentrated hydrides on ductility of Zircaloy 4 cladding. Zircaloy 4 plate specimens containing 300 to 800 wt ppm H and having hydrogen concentration gradients in the thickness or width direction were tensile tested at room temperature and 623 K. Ductilities of specimens differed depending on hydride distribution and test temperature. At room temperature, specimens with strong hydrogen concentration gradient had slightly higher total elongation than those with uniform hydrogen distribution. In the former specimen, slower crack propagation was observed in less hydrided part. At 623 K, specimens with uniform hydrogen distribution exhibited improved ductility, while specimens with strong hydrogen concentration gradient showed relatively smaller total elongation. (author)