The Contribution of Various Plasticity Mechanisms to the Deformation Behavior of Gradient Nanograined FeNi Alloy

Abstract

This paper investigates the deformation behavior of a gradient grained FeNi sample under uniaxial tension using molecular dynamics simulations. The simulated sample consists of five layers with grains of the same size in each layer ranging from 10 to 30 nm. It is shown that the sample plasticity develops through sequential activation of different mechanisms. These are either the generation of certain structural defects, or grain boundary migration, or grain boundary sliding. The onset of plasticity is provided by partial dislocations that produce stacking faults in large grains. Other mechanisms involved in plastic deformation are the nucleation of trailing/full dislocations and twinning, which gradually affect smaller and smaller grains. Grain boundary sliding is more intensive in smallest grains due to their less constraint. Grain boundary migration generally leads to the growth of large grains. At strains below 7.0%, plasticity is mainly contributed by the evolution of stacking faults. At higher strains, the main plasticity mechanisms are twinning and grain boundary migration. As the strain increases, the maximum values of accumulated shear, the density of intragranular defects, and the number of atoms involved in intergranular rearrangements are observed first in large, then in medium, and finally in small grains.

Deformation mechanisms based on the multiscale molecular dynamics of a gradient TA1 titanium alloy

“…30 The research findings of Korchuganov et al support the view that the plasticity of gradient-structured materials develops through the sequential activation of different mechanisms. 31 Numerous molecular dynamics simulation studies have shown that heterogeneous gradient nanocrystalline copper exhibits high strength and excellent toughness, which helps in improving and balancing the opposing characteristics of strength and toughness. 32,33 In polycrystalline copper, the gradient of grain size can improve the stability of grain boundaries and enhance the material's plasticity.…”

Fracture of Fe95Ni5 Alloys with Gradient-Grained Structure under Uniaxial Tension

“…Due to small grain sizes and high grain boundary density, plastic deformation in nanocrystalline materials is characterized by a high-flow stress. Plasticity occurs through lattice dislocation slip and grain boundary mechanisms [6][7][8][9]. Lattice dislocation slip is the main plasticity mechanism in nanocrystalline materials with grain sizes ranging from r c to 100 nm, where r c is the threshold grain size lying in the range of 10-30 nm for different materials and structures.…”

“…Computer simulations are widely used to study the deformation mechanisms of gradient-grained metallic materials. It is believed that the relationship between the gradientgrained structure and deformation mechanisms at the microscopic level can be most effectively modeled using the molecular dynamics method [8,9,[36][37][38][39][40][41][42][43][44]. Earlier, we numerically studied the deformation behavior of a gradient-grained FeNi sample under uniaxial tension [8].…”

“…It is believed that the relationship between the gradientgrained structure and deformation mechanisms at the microscopic level can be most effectively modeled using the molecular dynamics method [8,9,[36][37][38][39][40][41][42][43][44]. Earlier, we numerically studied the deformation behavior of a gradient-grained FeNi sample under uniaxial tension [8]. The simulations revealed the activation sequence and the degree of contribution of various mechanisms to the sample plasticity.…”

Deformation Behavior of Two-Phase Gradient Nanograined Fe95Ni5 Alloys under Different Types of Loading

“…Considerable study is currently given to heterogeneous metallic materials with a gradient grained structure, combining high strength and fracture toughness [23][24][25]. The calculation results showed that a higher grain size gradient improves the strength of materials [25].…”