Molecular Dynamics Simulation Study of the Mechanical Properties of Nanocrystalline Body-Centered Cubic Iron

Abstract

In the present work, the mechanical properties of nanocrystalline body-centered cubic (BCC) iron with an average grain size of 10 Å were investigated using molecular dynamics (MD) simulations. The structure has one layer of crystal grains, which means such a model could represent a structure with directional crystallization. A series of uniaxial tensile tests with different strain rates and temperatures was performed until the full rupture of the model. Moreover, tensile tests of the models with a void at the center and shear tests were carried out. In the tensile test simulations, peak stress and average values of flow stress increase with strain rate. However, the strain rate does not affect the elasticity modulus. Due to the presence of void, stress concentrations in structure have been observed, which leads to dislocation pile-up and grain boundary slips at lower strains. Furthermore, the model with the void reaches lower values of peak stresses as well as stress overshoot compared to the no void model. The study results provide a better understanding of the mechanical response of nanocrystalline BCC iron under various loadings.

Molecular dynamics simulations of TC4 titanium alloy with mechanical property calculations after various heat treatments

“…To compare experiments with simulations under the same heat treatment of annealing, solid solution at 1227 K and aging at 811 K, the simulated tensile strength is 11.471 GPa after annealing, and 12.388 GPa after additional solid solution and aging, which are both around 10 times that of the experimental values of 1054.93 MPa after annealing, and 1224.67 MPa after additional solid solution and aging. Overall, the simulated σ max is much higher than the experimental tensile strength, which has been attributed to a higher strain rate, 22 and lack of defects, impurities and dislocations in the MD models when compared with experimental specimens. 23,24…”

“…4, the elastic modulus is computed to be 149.1 GPa for tension along the [0001] direction, higher than the 90.8 GPa along the [2À1À10] direction. For tension along the [0001] direction, s max is consistently higher than that of the Overall, the simulated s max is much higher than the experimental tensile strength, which has been attributed to a higher strain rate, 22 and lack of defects, impurities and dislocations in the MD models when compared with experimental specimens. 23,24 In OVITO, polyhedral template matching is used to identify the crystal structure with red, green, blue and gray atoms which represent HCP, FCC, BCC and other (or irregular) structures respectively in Fig.…”

Molecular dynamics study of the effect of hydrogen on the diffusion and tensile of polycrystal Fe with void defect

“…In order to investigate the mechanical response of the model with void and hydrogen atoms, we conducted uniaxial tensile to compare the difference of stress-strain curves under different hydrogen content and different tensile strain rates. First, the temperature is set to 300 K, the strain rate is set to 0.006/ps [22] , the tensile direction is y axis, and the total strain rate is 60%.…”

“…Since it is difficult to provide atomic details in experiments, molecular dynamics simulation (MD) can not only verify theoretical results, but also provide reference for experimental results. Jan Herman [12] simulated the dislocation accumulation and low-strain grain boundary slip caused by voids in single-layer polycrystal iron by MD method. Hadi [13] studied the deformation behavior of carbon-containing polycrystal iron by combining MD with quantitative atomic displacement analysis.…”

A Unified Empirical Equation for Determining the Mechanical Properties of Porous NiTi Alloy: From Nanoporosity to Microporosity

“…This rate differs from the experimental strain rate, which can lead to overestimation of mechanical properties in the case of molecular dynamics simulation, for example, as shown in Refs. [68,69]. The value of the stress σ xx was determined using the Irving-Kirkwood equation [70]:…”