Effect of grain boundary misorientation on the apparent diffusivity in nanocrystalline aluminum by atomistic simulation study

Abstract

To obtain a fundamental understanding of the effect of structure and geometry of grain boundary on the diffusion kinetics in nanocrystalline materials, the influence of grain boundary misorientation on the effective diffusion coefficient (apparent diffusivity) in nanocrystalline aluminum was investigated using molecular dynamics simulations. Nine series of [001] symmetric tilt grain boundaries, including high and low symmetric boundary planes, were studied. The apparent diffusivity in the samples was calculated in the temperature range from 423 K to 823 K by monitoring the mean square displacement of atoms as a function of simulation time. A temperature dependence of the effective diffusion coefficient according to the Arrhenius law was obtained for all samples. It is found that the apparent diffusivity is anisotropic and it is a strong function of grain boundary misorientation at low and high temperatures. At all temperatures, Σ29 [001]/(520) symmetric tilt grain boundary with misorientation angle of 43.68° exhibits the highest effective diffusion coefficient among the investigated grain boundaries. The simulation results show that the activation energy and pre-exponential factor are affected significantly by the grain boundary misorientation angle. Moreover, the results indicated that the misorientation dependence of activation energy for diffusion exhibits two local maxima, which correspond to two symmetric tilt grain boundaries. Additional calculation of misorientation dependence of the pre-exponential factor shows two local minima at the same symmetric tilt grain boundaries. The misorientation dependence of the effective diffusion coefficient was explained on the basis of grain boundary energy and the crystallographic structure of grain boundary.

Combined crystal plasticity and grain boundary modeling of creep in ferritic-martensitic steels: II. The effect of stress and temperature on engineering and microstructural properties

“…grain boundary diffusivity) are the same for each grain boundary in the model. In actuality the crystallography of the grain boundary affects the values of these parameters (see [40][41][42]). A more realistic model would represent a distribution of parameters as a function of the grain boundary misorientation distribution.…”

Exploiting grain boundary diffusion to minimize dendrite formation in lithium metal-solid state batteries

“…For an equilibrium concentration of vacancies, the bulk diffusivity, D eq , can be obtained from eqn (5), 30,31…”

“…For an equilibrium concentration of vacancies, the bulk diffusivity, D eq , can be obtained from eqn (5), 30,31 where and D * denote, respectively, the non-equilibrium vacancy fraction used in the simulations and the diffusivity predicted by MD. D eq was adopted as the bulk diffusivity and was used below to estimate the polycrystalline diffusivity.…”

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

“…It is investigated that increasing grain size ratio of dislocation glide mechanisms gets higher than GB slip [7]. Since the diffusion of atoms has a high effect on deformation behavior [18][19][20][21], it is presented that the diffusion coefficient is highly increased by prestraining, especially at lower temperatures [22]. Furthermore, it is investigated that high strain rates cause GB shearing to be a more superior deformation mechanism than diffusion-based ones [10,23,24].…”