Molecular dynamics simulations of tensile and creep-ratcheting behaviour of CNT reinforced columnar nanocrystalline Al nanocomposites

Abstract

High-temperature cyclic loading is a major factor affecting the life of a structural component. In this study, the tensile and creep-ratcheting behaviour of three volume fractions of CNT-reinforced columnar nanocrystalline aluminium has been studied using hybrid potentials (EAM, AIREBO and LJ potentials) at two different stress ratios (R = 0.4, 0.6) and three different temperatures (T = 300 K, 467 K and 653 K). The aim is to determine the stress-strain curve, strain-time curve, overall dislocation density, dislocation types, and mainly the underlying deformation mechanisms of CNT-based NC Al matrix nanocomposites. Increasing the CNT volume fraction in the matrix has shown improved UTS values, enhanced dislocation annihilation rate, dissipation of the hysteresis loop energy, lower strain accumulation and higher time to fracture. The specimen fails quickly at higher temperatures which is depicted by the widening of the hysteresis loop. The predominant deformation mechanisms like grain boundary diffusion, widening, merging, sliding and rotations have been observed. Grain boundary diffusion drives the creep-ratcheting deformation behaviour under three temperatures and the misalignment has been noticed at the interaction of CNT-NC Al nanocomposite during the creep-ratcheting deformation at high temperature. The Shockley-partial and perfect dislocations have been determined to control the underlying deformation mechanism. The current work can serve as a keystone in the creep-ratcheting analysis of structural materials employed in high-temperature loading environments.