Effect of irradiation in different velocity vectors on the mechanical properties of Nickel single crystal using Molecular dynamic simulation

Abstract

In this work, molecular dynamics (MD) based simulation were performed to study the effect of radiation induced defects on the mechanical properties and deformation mechanism of nickel single crystal. Nickel single crystal is created by filling nickel atoms (FCC crystal structure, a = 3.50 Å) under periodic boundary conditions in simulation box of 100 Å3. EAM potential is used to model the interactions between Ni-Ni atoms. The simulation was carried out in two phases and in the first phase, the modeled single crystal is irradiated with 1 keV and 3 keV incident energies using primary knock on atom (PKA) method in three different velocity vectors [1 1 1], [1 1 2] and [5 3 1]. Due to this irradiation effect the sample has undergone abrupt changes, and a large number of defects like vacancies and interstitials have formed. The impact of the velocity vector is different with different incident energies, and there is a minimum number of vacancies generation with [1 1 1] velocity vector. The amorphization at PKA region can be observed in the irradiated sample using radial distribution function (RDF). In the second phase of simulation, the irradiated samples were tensile tested at a temperature of 300 K at a strain rate of 1010 s-1. There is a substantial decrease of yield strength and Y modulus in the irradiated nickel samples (due to the formation of defects) when compared with that of the unirradiated nickel sample. Due to different velocity vectors within the incident energy, there was a slight variation in the mechanical properties as observed from the stress-strain graphs. Deformation mechanism features such as dislocations, partial dislocations and surface defects such as stacking faults are observed in the deforemd samples.