Grain boundary induced deformation mechanisms in nanocrystalline Al by molecular dynamics simulation: From interatomic potential perspective

Abstract

Nanocrystalline metals exhibit many excellent mechanical properties and their underlying deformation mechanisms have been studying widespread. The well-designed atomistic simulations can predict the mechanical behavior of materials ahead of experiments and provide sufficient information on the atomic scale. The choice of appropriate interatomic potential is one of the main concerns of any atomistic simulation that needs to be seriously considered in order to obtain reliable results. In this study, we investigated the mechanical response and the deformation mechanisms of nanocrystalline Al under uniaxial loading by molecular dynamics (MD) simulations with different embedded atom method (EAM) interatomic potentials. The selection of potential has a significant influence on the simulation result, and the reliability of these potentials was evaluated based on the available experimental data in the literature. In the elastic stage, the stress-strain response and Young's modulus of the simulated samples varied with different potentials. Three independent elastic constants of single crystal Al were used to predict the isotropic elastic modulus of the polycrystal Al sample. In the plastic stage, multiple grain boundary (GB) induced deformation mechanisms were observed, including GB migration, intergranular fracture, dislocation nucleation from GB, and deformation twinning. The generalized stacking fault energies of Al were calculated by MD simulation using different potentials, and their effects on the dislocation nucleation and deformation twinning mechanisms were discussed. This work signifies the important role of GBs play in nanocrystalline metals during plastic deformation and highlights the significance of using the appropriate interatomic potential for a specific simulation problem.Abstract: Nanocrystalline metals exhibit many excellent mechanical properties and their underlying deformation mechanisms have been studying widespread. The well-designed atomistic simulations can predict the mechanical behavior of materials ahead of experiments and provide sufficient information on the atomic scale. The choice of appropriate interatomic potential is one of the main concerns of any atomistic simulation that needs to be seriously considered in order to obtain reliable results. In this study, we investigated the mechanical response and the deformation mechanisms of nanocrystalline Al under uniaxial loading by molecular dynamics (MD) simulations with different embedded atom method (EAM) interatomic potentials. The selection of potential has a significant influence on the simulation result, and the reliability of these potentials was evaluated based on the available experimental data in the literature. In the elastic stage, the stress-strain response and Young's modulus of the simulated samples varied with different potentials. Three independent elastic constants of single crystal Al were used to predict the isotropic elastic modulus of the polycrystal Al sample. In the plastic stage, multiple grain boundary (GB) induced de...

Low friction of metallic multilayers by formation of a shear-induced alloy

“…Note that grain boundary-mediated scenarios included in Yamakov’s deformation model 34 have also been suggested for the plasticity of other material systems such as the deformation mechanism of the Al-Cu joint under tensile loading 35 and grain size dependence of tensile behavior in nanocrystalline Ni-Fe 36 . Also, atomistic simulations are able to shed further light on grain boundary-induced deformation (see eg 37,38 ). On the other hand, the multilayer system with a layer thickness of 100 nm resulted in different behavior which means that dislocation-mediated deformation should be in charge for the observed higher friction behavior.…”

Prediction on Mechanical Properties of Non-Equiatomic High-Entropy Alloy by Atomistic Simulation and Machine Learning

“…This deviation is mainly attributed to the grain boundaries in the polycrystal sample. Experiments and simulations have proved that the existence of grain boundaries has an important effect on the mechanical properties of materials [41][42][43][44]. As mentioned, the yield stress depends mainly on the nucleation of the first set of dislocations [24].…”

“…On the other hand, Young's modulus is sensitive to the chemical composition and the intrinsic structure of materials. Simulations have shown that Young's modulus decreases with the increase of the grain boundary volume fraction [43], especially when the grain size drops to the nanocrystalline region (<100 nm) [44]. While the single-crystal sample has a single fcc structure (green atoms), and for the polycrystal samples, the atoms at grain boundary regions contribute a new disordered structure (blue atoms).…”

Atomistic Study of the Effect of Magnesium Dopants on the Strength of Nanocrystalline Aluminum

“…In this study, we used atomistic simulations to explore the underlying atomic-level mechanisms of GB segregation strengthening of NC Al by doping Mg atoms. Fully three dimensional (3D) polycrystalline models for both pure Al and Al-5%Mg were used to avoid the geometric limitations of 2D or 3D columnar polycrystalline models [20]. A hybrid MC/MD method was used to obtain the equilibrium distribution of Mg atoms in the Al-Mg alloy model.…”