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Atomistic simulations of solid
solution strengthening of α-iron
報告者:郭正宇
日期:2011.12.26
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Outline
• Introduction
• Model
• Results
• Summary
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Introduction
1. Solid solution strengthening achieved by alloying of small amounts of
dissolved atoms is one of the most important mechanisms of
strengthening in α-iron. So far this mechanism has not been analyzed
by molecular dynamics simulations in great detail.
2. The MD method permitted explicit treatment of ‘‘core” effects, dislocation
pinning and deceleration, and dislocation unpinning by thermal
activation, all under an applied external load.
3. The idea of the present paper is thus to simulate dislocation slide in an
α-iron crystal under external shear stresses in the presence of
interstitially and substitutionally dissolved atoms.
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Model
Fig. 1 Schematic illustration of the simulation box containing a single
dislocation under external shear deformation.
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Disregistry [b]
Results
Position along the glide plane [nm]
(a)
(b)
Fig. 2 Detection of dislocations in bcc-structures: (a) lattice plane with edge dislocation,
(b) relative displacements of atoms across the slide plane
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Results
100 MPa
50 MPa
40 MPa
20 MPa
Fig. 3 Visualization of a configuration of an
edge dislocation (red) and dissolved atoms
(blue).
Fig. 4 Four different types of dislocation
movement in a solid solution as a function
of external shear stress magnitude.
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Results
α-Fe/Cu 0.0 %
(a)
α-Fe/Ni
(b)
Fig. 5 Average glide velocity of edge dislocations in dependence of the external shear stress
and as a function of the concentration of dissolved atoms: (a) Cu-dissolved atoms and (b) Nidissolved atoms.
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α-Fe/
Cu
Ni
Yield stress increase [MPa]
Results
Dissolved atoms (mass.-%)
Fig. 6 Critical shear stress sc in dependence of
the concentration of dissolved Cu and Ni
atoms.
Fig. 7 Yield stress increase of a-Fe for small
concentrations of dissolved atoms
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Summary
1. Solid solution strengthening was determined for different concentrations
of Cu and Ni atoms. It was found that the movement of edge dislocations
in the case of Ni atoms was nearly unhindered in contrast to the case
when Cu atoms were present.
2. The critical shear stress for dislocation movement was found to be
Significantly higher for Cu-alloyed a-iron as compared to Ni-alloyed a-iron.
3. Interstitial C atoms in a-iron are significantly stronger obstacles for the
dislocation movement than substitutional Cu atoms.
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Thanks for your attention