Abstract
The shear-induced coupled grain boundary motion plays an important role in the deformation of nanocrystalline (NC) materials. It has been known that the atomic structure of the grain boundary (GB) is not necessarily unique for a given set of misorientation and inclination of the boundary plane. However, the effect of the structural multiplicity of the GB on its coupled motion has not been reported. In the present study we investigated the structural multiplicity of the symmetric tilt Σ5(310) boundary in aluminium and its influence on the GB behaviour at a temperature range of 300 K–600 K using molecular dynamic simulations. Two starting atomic configurations were adopted in the simulations which resulted in three different GB structures at different temperatures. Under the applied shear deformation each GB structure exhibited its unique GB behaviour. A dual GB behaviour, namely the transformation of one GB behaviour to another during deformation, was observed for the second starting configuration at a temperature of 500 K. The atomistic mechanisms responsible for these behaviour were analysed in detail. The result of this study implicates a strong relationship between GB structures and their behaviour, and provides a further information of the grain boundary mediated plasticity in nanocrystalline materials.
Highlights
Grain boundary (GB) migration is defined as the movement of a grain boundary in perpendicular direction to the boundary plane, and it plays an important role in recrystallization, grain growth, and the plasticity of nanocrystalline (NC) materials
Merkle and Smith[34] observed the atomic structures of NiO bicrystals near Σ = 5(310) and Σ = 13(510) GBs in a high resolution transmission electron microscopy (HRTEM), and found that: (1) several different grain boundary structures existed for each GB; (2) asymmetric structural units were quite common, even in symmetric GB’s; (3) the Σ 13(510) boundary deviated on an atomic scale from a planar configuration in analogy to surface roughening or surface reconstruction
In the present study we investigated the structural multiplicity of the symmetric tilt Σ 5(310) boundary in aluminium and its influence on GB behaviour by molecular dynamics simulations and found that the GB structural multiplicity did affect the GB behaviour
Summary
Grain boundary (GB) migration is defined as the movement of a grain boundary in perpendicular direction to the boundary plane, and it plays an important role in recrystallization, grain growth, and the plasticity of nanocrystalline (NC) materials. The deformation of the boundaries was found to operate by three modes, depending on the GB equilibrium configuration: GB sliding by uncorrelated atomic shuffling, nucleation of partial dislocations from the interface to the grains, and GB migration Zhang and his co-workers conducted molecular dynamics simulations to study elastically driven GB migration[27], curvature driven GB migration[28], and shear stress-driven GB migration[29]. Cahn et al.[30] and Suzuki and Mishin[31] carried out molecular dynamics simulations to investigate the stress-induced migration of [001] symmetrical tilt GBs in copper, and provided a detailed description of the atomic motions during the coupled GB motion They found that the GB coupling factor is a geometric constant whose value can be predicted from simple geometric considerations, and they identified two distinct modes of coupled GB motion. A detailed analysis has been carried out to gain a deeper understanding of the atomistic mechanism of GB coupled motion
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