Texture and yielding anisotropy of Zircaloy-4 alloy cladding tube produced by cold Pilger rolling and annealing

Abstract

Crystal orientation and mechanical properties of Zircaloy-4 (Zr-4) alloy cladding tube manufactured by cold Pilger rolling and annealing were systematically investigated. Electron Back-Scattered Diffraction (EBSD) analysis showed that grains, which were fully recrystallized in α phase, were strongly oriented with their c axis parallel to the tangential direction (TD) of the tube and, meanwhile, their normal direction of {112¯0}α planes parallel to the axial direction (AD). Compression tests carried out along three loading directions (TD-0°, TD-45° and AD, respectively) at room temperature revealed that the Zr-4 alloy tube exhibit strong yielding anisotropy: TD-0°＞TD-45°＞AD. Meanwhile, the alloy exhibited strain rate hardening effect, since the yield strength increased with the growing strain rate. The relationship between texture and yielding anisotropy of the Zr-4 alloy tube was further discussed based on Schmid factor theory. The Schmid factor values for basal, prismatic and pyramidal <a> slip systems, which were three important yielding mechanisms in Zr-4 alloy during the compression, were calculated depending on the geometric relationship between loading directions and crystallography. Calculation results revealed that there was an inverse relationship between Schmid factor value for slip modes and the compression yield strength of the Zr-4 alloy.