Abstract
The formation mechanism considers fivefold deformation twins originating from the grain boundaries in a nanocrystalline material, resulting in that fivefold deformation twins derived from a single crystal have not been reported by molecular dynamics simulations. In this study, fivefold deformation twins are observed in a single crystal of face-centered cubic (fcc) alloy. A new formation mechanism is proposed for fivefold deformation twins in a single crystal. A partial dislocation is emitted from the incoherent twin boundaries (ITBs) with high energy, generating a stacking fault along {111} plane, and resulting in the nucleating and growing of a twin by the successive emission of partials. A node is fixed at the intersecting center of the four different slip {111} planes. With increasing stress under the indentation, ITBs come into being close to the node, leading to the emission of a partial from the node. This generates a stacking fault along a {111} plane, nucleating and growing a twin by the continuous emission of the partials. This process repeats until the formation of fivefold deformation twins.
Highlights
The formation mechanism considers fivefold deformation twins originating from the grain boundaries in a nanocrystalline material, resulting in that fivefold deformation twins derived from a single crystal have not been reported by molecular dynamics simulations
Fivefold deformation twins derived from a single crystal are not predicted by Molecular dynamics (MD) simulations
This is attributed to that the formation mechanism of fivefold deformation twins explains, that a simple twin is generated through partial dislocation emissions from GBs5–8,10,12,14,16,17, resulting in the fivefold deformation twins observed in nc metals7,8,10,12,14,17
Summary
The formation mechanism considers fivefold deformation twins originating from the grain boundaries in a nanocrystalline material, resulting in that fivefold deformation twins derived from a single crystal have not been reported by molecular dynamics simulations. FTs are usually observed in grains of nanowires, nanoparticles and nc metals, whereas rarely found in single crystals and macroscopic materials, except occasionally in highly deformed metals, such as ball milling and high pressure torsion. FTs are usually observed in grains of nanowires, nanoparticles and nc metals, whereas rarely found in single crystals and macroscopic materials, except occasionally in highly deformed metals, such as ball milling and high pressure torsion9–11 This raises an issue for the formation mechanism of fivefold deformation twins in the single crystals and macroscopic materials for pragmatic engineering applications. MD simulations dominate nc and constructed models, other than a single crystal This results in the interpretation that formation of FTs, is through the emission of partial dislocations from the grain boundaries (GBs). The formation mechanism of fivefold deformation twins is investigated in a single crystal under nanoindentation via plastic deformation
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