Roles of texture in controlling oxidation, hydrogen ingress and hydride formation in Zr alloys

This review article attempts to provide an overall description for the texture related issues of degradation of Zr alloys. Experimental observations show that the oxide formed on Zr alloys is strongly textured. The texture and grain-boundary characteristics of oxide are dependent on the texture of metal substrate. Computer simulation and thermodynamic modeling were used to explain the influence of metal substrate on structure of oxide film, and intrinsic factors affecting the oxide microstructure. Models of diffusion process of hydrogen atoms and oxygen diffusion through oxide are presented. Both intragranular and intergranular hydrides were found following (0 0 0 1)α-Zr||{1 1 1}δ-ZrH1.5 relationship under no load, but different relationships were observed under stress. The through-thickness texture inhomogeneity in fuel cladding tubes, the effects of hoop stress on the hydride orientation and the formation of interlinked hydride structure were studied. A thermodynamic model was developed to analyze the nucleation and the stress-induced reorientation of intergranular hydrides. These works provide a framework for understanding the effects of texture on the oxidation, the hydrogen ingress and the hydride formation in Zr alloys.