Abstract
As for magnesium (Mg) alloys, it has been noted that they are inferior to plastic deformation, but improvement in the mechanical properties by further refinement of grain size has been recently suggested. It means the importance of atomistic view of polycrystalline interface of Mg crystal. In this study, to discuss the deformation mechanism of polycrystalline Mg, atomistic grain boundary (GB) models by using coincidence site lattice (CSL) theory are constructed and are simulated for their relaxed and deformatted structures. First, GB structures in which the axis of rotation is in [11¯00] direction are relaxed at 10 Kelvin, and the GB energies are evaluated. Then, the deformation mechanism of each GB model under uniaxial tensile loading is observed by using the molecular dynamics (MD) method. The present MD simulations are based on embedded atom method (EAM) potential for Mg crystal. As a result, we were able to observe atomistically a variety of GB structures and to recognize significant difference in deformation mechanism between low-angle GBs and high-angle GBs. A close scrutiny is made on phenomena of dislocation emission processes peculiar to each atomistic local structure in high-angle GBs.
Highlights
In recent years, improvement of fuel efficiency of the transportation equipment is demanded to reduce burden on the environment
By using conventional version of common neighbor analysis (CNA), an atom is primarily recognized as face-centered cubic (FCC), body-centered cubic (BCC), or hexagonal close-packed (HCP) structure
The energy graph shows one sharp cusp, which is well observed in other pure metals or alloys, via experiment [31] and computation [32]. This indicates that atoms in this grain boundary (GB) structure are regularly and compactly arranged on GB plane to exhibit the most stable structure
Summary
Improvement of fuel efficiency of the transportation equipment is demanded to reduce burden on the environment. There is an issue concerning weight saving of the transportation equipment For those purposes, one of the materials that attract much attention of researchers now is magnesium (Mg) alloy. There comes an idea that grain refining process will resolve this problem This method reduces individual particle sizes in a polycrystal and raises the density of grain boundaries (GBs). Within the context of the effect of GB on plastic deformation of Mg like in the present study, polycrystalline MD models (though composed of nanosized grains) have been investigated and those studies are giving many insights as for deformation mechanism around GB region [19,20,21,22,23]. The relationship between GB energy and GB structures and the relationship between the deformation mechanism and the GB structures in deforming state are discussed too
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