Regularities of Thermal Expansion of Cladding Tubes and Rods Made of E110opt Alloy within the Temperature Range of 273–1473 K (20–1200°C)

The regularities of the thermal expansion of cladding tubes and rods from the E110opt alloy, as well as the anisotropy of their thermal properties in the case of layer-by-layer texture inhomogeneity are studied. The thermal linear expansion coefficients (TLEC) of rods and cladding tubes were measured in the axial, radial and tangential directions during heating and cooling in the temperature range of 293–1473 K (20–1200°C). It is shown that as a result of α → β → α phase transformations in the samples, a stable texture of phase transformations is formed which is preserved during subsequent heating and cooling cycles. Analytical expressions are obtained that describe the temperature dependence of the thermal expansion coefficient in the first cycle of heating products from the E110opt alloy, taking into account possible α → β phase transformations and the resulting α-Zr crystal lattice deformation along the a and c axes. It was established that the presence of layer-by-layer inhomogeneity in the samples leads to the appearance of stresses between layers with different crystallographic textures and, as a result, affects the orientation dependence of phase transformations that are sensitive to the stress state in the material. The results obtained indicate the need to take into account the internal stresses arising in textured anisotropic materials during heating and cooling, and to separate the contributions of thermal expansion and plastic deformation when analyzing data from dilatometric measurements of sample sizes..