Recrystallization of cladding tubes from Zr-based alloys for nuclear reactors

Abstract

This paper is devoted to the regularities of change in the crystallographic texture and the structure of cladding tubes with a total degree of deformation by their cross-section of 70-80% as a result of polygonization or recrystallization during heat treatment in the temperature range from 480 to 600 °C. It is shown, that there are two competing processes of crystal lattice perfection in cladding tubes at annealing temperatures over 540 °C. The oriented growth of grain nuclei, formed at the boundaries of grains and disoriented with respect to the deformed matrix by an angle of 20-30° about basal axes, is predominant. At the recrystallization of cladding tubes from E110 alloy, a significant change in their crystallographic texture of cold rolling is observed, i.e. an increase of the integral texture parameter fr increases, and a decrease of fT. The grains, formed at the stage of plastic deformation by twinning, prove to be unstable even at the stage of polygonization, due to the mobility of highly disoriented boundaries under conditions of the anisotropic thermal expansion of neighboring regions.