Detwinning of High-Purity Zirconium: In-Situ Neutron Diffraction Experiments

Abstract

Twinning is an important deformation mode in hexagonal metals to accommodate deformation along the c-axis. It differs from slip in that it accommodates shear by means of crystallographic reorientation of domains within the grain. Such reorientation has been shown to be reversible (detwinning) in magnesium alloy aggregates. In this paper we perform in-situ neutron diffraction reversal experiments on high-purity Zr at room temperature and liquid nitrogen temper- ature, and follow the evolution of twin fraction. The experi- ments were motivated by previous studies done on clock-rolled Zr, subjected to deformation history changes (direction and temperature), in the quasi-static regime, for temperatures ranging from 76 K to 450 K. We demonstrate here for the first time that detwinning of 1012 1011 tensile twins is favored over the activation of a different twin variant in grains of high-purity polycrystalline Zr. Avisco-plastic self-consistent (VPSC) model developed previously, which includes com- bined slip and twin deformation, was used here to simulate the reversal behavior of the material and to interpret the experi- mental results in terms of slip and twinning activities.