Elastic stiffness tensors of Zr–xNb alloy in the presence of defects: A molecular dynamics study

Abstract

In a nuclear reactor, the Zr-xNb alloy, which is used as a structural material in the core region, is irradiated by energetic particles that cause the atoms to be displaced from their lattice sites and giving rise to crystal defects. The local changes in the atomic arrangements lead to local deformations of the solid and thereby changes of its local mechanical properties. Understanding the mechanisms behind this evolution in the core region of a reactor, and its monitoring or controlling is a critical task in nuclear industry. In this work, using extensive molecular dynamics simulations, we have studied the effects of radiation damage on the local mechanical properties of Zr-xNb alloy. In the first step, the effect of Nb-concentration on the mechanical stability of homogeneous Zr-xNb alloy is investigated. In the second step, we have studied the local changes of the elastic constants due to local changes of the microstructure. These local changes include presence and accumulation of vacancies in the form of dislocation loops or voids, accumulation of Nb atoms in the form of clusters of different morphologies. This study covers both cases of T = 0 • K and finite temperatures up to T = 600 • K.

Molecular Dynamics Study of Microstructural Evolution and Damage-Depth Induced by Isotropic Irradiation on Zr-1%Nb Alloy

“…The macroscopic properties of nuclear materials are highly sensitive to the microstructural evolution of atoms in the materials and other parameters such as temperature and pressure. The present authors have already studied the mechanical properties of Zr-1%Nb alloy in the presence of defects [9,10]. Also, other studies have been done by others [7][8][11][12][13][14][15][16][17][18][19][20] and some aspects of this alloy and other similar materials have been considered until now.…”

Analysis of Irradiation Induced Defect Clusterization for Zr-1%Nb Alloy Using Atomistic Simulation

“…The interatomic potential used for the Zr-Nb binary system was an angular-dependent potential (ADP) [22]. This kind of interatomic model potential has been mostly used for metals and metal alloys and it is a generalization of an embeddedatom model (EAM) potential that includes both dipole and quadrupole distortions of the local environment of an atom which has been shown to reproduce a wide range of properties [8]. The convergency of the size dependence of the simulation box for the calculation of impurity formation energy has been achieved for 2592 atoms in a 3×3×3 supercell composed of the unit cell with 96 atoms.…”

“…Extensive research has already been conducted on the properties of zirconium-niobium alloys. For example, the evolution of mechanical properties with defects has been studied by some of the present authors [8][9]; the vacancy formation and self-interstitial clusterization under irradiation for pure zirconium have been studied by Maxwell and coworkers [10]; the mechanical properties of zirconium alloys and zirconium hydrides were studied by Weck and his coworkers [11]; according to Singh and colleagues, the fracture behavior of bi-crystalline zirconium-niobium alloys was examined with different niobium percentages [12]. Additional studies on the properties of Zr-Nb alloy and similar materials can be found in the literature [13][14][15][16][17][18][19][20].…”

“…In Ref. [8], the authors have already investigated some properties for different values of Nb concentrations.…”