Prediction of Mechanical Properties of Steel Nanowires using Molecular Dynamics

Abstract

Nanowires have received increasing interest due to their unique properties and potential applications [1]. Limited studies have been conducted on tensile strength and mechanical properties of pure iron and iron alloy-based nanowires using simulations. In this study, the dependence of the mechanical properties of steel nanowires with different carbon percentages at varying temperatures is investigated. Atomic interactions between Fe and C atoms are modelled using interatomic force fields for molecular dynamics (MD) simulations. Four interatomic potentials were evaluated [2][3][4][5][6] using their bulk properties. Modified embedded atom method (MEAM) potential by Liyanage et al. was selected due to its accuracy in predicting properties of BCC Fe, Fe-C in B1 rock salt structure, and properties of BCC iron structure with varying C percentages. Uniaxial tensile test simulations at varying C atom percentages and different temperatures are conducted using MD simulations with the LAMMPS package. The amount of C was varied from 0 – 10 % at temperatures ranging from 0.1 K – 900 K. Mechanical properties of steel nanowires were extracted from the stress-strain curves generated by the tensile simulations. Young’s modulus of the steel nanowires increased in the temperature range of 0.1 K – 300 K while decreased in the range of 600 K - 900 K with respect to the C %. Yield stress and Ultimate Tensile Stress gradually decreased with the increase of C atoms from 0 – 10 %. Predicted results were compared with the results of bulk steel experimental values [7]. The micro-structural changes in the nanowires were analysed with common neighbor analysis (CNA). CNA showed the rapid formation of slip planes with increasing C% and increased propagation of slip planes contributes to the reduction in the strength of the nanowires.