<i>Ab Initio</i> Study of Tin Segregation in Zirconium at the Σ17(0̅337) Tilt Grain Boundary

Abstract

Zircaloy-2 and zircaloy-4 contain alloying elements that improve their mechanical properties and corrosion resistance. However, the segregation of these alloying elements affects considerably these properties. In this work, the steps of constructing a symmetrical tilt grain boundary in hcp structure are described and the segregation energy of Sn in the symmetric tilt grain boundary Σ17[θ = 49.71 • /[2110], (0337)] in Zr is also calculated using the first principles ab initio and the ABINIT calculation code. Among five selected pseudopotentials, the optimization and convergence calculations for the bulk hcp Zr lattice show that the most optimal pseudopotentials are GGA-PBE-HGH and GGA-PBE-Troullier Martins (TM) and a good agreement was found with previous theoretical and experimental data. The segregation energy calculations show that the segregation of Sn at the sites of symmetric tilt grain boundary plane is unfavourable, while it is favourable at the sites of the first plane parallel to the grain boundary plane. However, for the other planes, the segregation is unfavourable. From an energetic point of view, it is not appropriate for the Sn to replace the Zr atom in the studied grain boundary, which was demonstrated by the charge density maps.