Abstract
The interaction between interstitial oxygen atoms and <a>-type screw dislocations was investigated via first-principles calculations to elucidate the effect of oxygen solutes on the deformation behaviors of Mg. The results show that repulsive interactions exist between basal screw dislocation cores and oxygen atoms, which would enable the full basal dislocation to bypass the oxygen atoms in the dislocation glide plane through the cross-slip process. This repulsion also increases the resistance to the motion of dissociated basal dislocations. Moreover, the energy of prismatic <a>-type screw dislocation cores is reduced by the presence of oxygen, which would stabilize the screw dislocation core on the prismatic plane, accordingly facilitating the prismatic slip. This information can complement the fundamental knowledge of alloying Mg using interstitial solutes.
Highlights
Magnesium has a low density and high strength to weight ratio, which renders it suitable for substituting Fe- and Al-based alloys in the areas of automobile and aerospace [1]
In the other two hexagonal close-packed (HCP) metals, Zr and Ti, researchers have discovered that interstitial oxygen atoms would increase the lattice friction against the glide of screw dislocation, significantly influencing the plasticity of Zr and Ti [9,10,11]
The location and type of dislocations were determined by the dislocation analysis (DXA) in OVITO code [21,22], which could identify the dislocation line and discern HCP, face-centered cubic (FCC), and ‘other structures’ corresponding to the perfect lattice, stacking fault, and dislocation core region in the lattice, respectively
Summary
Magnesium has a low density and high strength to weight ratio, which renders it suitable for substituting Fe- and Al-based alloys in the areas of automobile and aerospace [1]. The influence of interstitial solutes, such as nonmetallic elements (C, N, O, and H), on the mechanical properties of magnesium has been seldom regarded. Using ab initio calculations, Ventelon et al [8] found that carbon atoms would induce the reconstruction of screw dislocation core in Fe, and be accountable for the solute-segregation related phenomena, such as yielding and strain aging in Fe–C alloy systems. In the other two hexagonal close-packed (HCP) metals, Zr and Ti, researchers have discovered that interstitial oxygen atoms would increase the lattice friction against the glide of screw dislocation, significantly influencing the plasticity of Zr and Ti [9,10,11]. The aforementioned studies on interstitial nonmetallic alloying elements invoke us to speculate whether the mechanical properties of Mg can be tuned by the solutionization of nonmetallic elements
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