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Atomistic simulation of tensile deformation behavior of ∑5 tilt grain boundaries in copper bicrystal.

Zhang L, Lu C, Tieu K - Sci Rep (2014)

Bottom Line: The results show that the ∑5 asymmetric GBs with different inclination angles (φ) are composed of only two structural units corresponding to the two ∑5 symmetric GBs.Tensile deformation is applied under both 'free' and 'constrained' boundary conditions.Simulation results revealed different mechanical properties of the symmetric and asymmetric GBs and indicated that stress state can play an important role in the deformation mechanisms of nanocrystalline materials.

View Article: PubMed Central - PubMed

Affiliation: School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522, Australia.

ABSTRACT
Experiments on polycrystalline metallic samples have indicated that Grain boundary (GB) structure can affect many material properties related to fracture and plasticity. In this study, atomistic simulations are employed to investigate the structures and mechanical behavior of both symmetric and asymmetric ∑5[0 0 1] tilt GBs of copper bicrystal. First, the equilibrium GB structures are generated by molecular statics simulation at 0K. The results show that the ∑5 asymmetric GBs with different inclination angles (φ) are composed of only two structural units corresponding to the two ∑5 symmetric GBs. Molecular dynamics simulations are then conducted to investigate the mechanical response and the underlying deformation mechanisms of bicrystal models with different ∑5 GBs under tension. Tensile deformation is applied under both 'free' and 'constrained' boundary conditions. Simulation results revealed different mechanical properties of the symmetric and asymmetric GBs and indicated that stress state can play an important role in the deformation mechanisms of nanocrystalline materials.

No MeSH data available.


Related in: MedlinePlus

Snapshots of Cu bicrystal with ∑5 (φ = 11.31°) GB at different deformation stage under free tension boundary condition.Images are colored according to the CNA parameter. Atoms with perfect fcc structures are removed to facilitate viewing of the defective structures. Atoms colored with yellow organize the GB plane and the dislocation core, while the blue atoms represent the stacking fault.
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f5: Snapshots of Cu bicrystal with ∑5 (φ = 11.31°) GB at different deformation stage under free tension boundary condition.Images are colored according to the CNA parameter. Atoms with perfect fcc structures are removed to facilitate viewing of the defective structures. Atoms colored with yellow organize the GB plane and the dislocation core, while the blue atoms represent the stacking fault.

Mentions: Fig. 5 shows the atomic details of Cu bicrystal with ∑5 (φ = 11.31°) GB at different deformation stages under free boundary condition. Atoms are colored by the CNA parameter and remove the atoms with fcc structures to facilitate the defective structures. The GB region expands and becomes coarsened when deformation occurs. Then, partial dislocations with Burger's vectors b = (1/6)[1 1 2] and b = (1/6)[1 1 −2] are nucleated in the lower grain region, as shown in Fig. 5 (b) at ε = 7.3%. However, unlike the case of ∑5 (φ = 0°) GB, dislocation nucleates into only one crystal lattice when the maximum tensile stress has been reached. This phenomenon can be attributed to the asymmetric GB with different orientation angles in the two lattices. Partial dislocations are nucleated and emitted continuously into the lower grain until the tensile strain reaches ε = 7.6%, as shown in Fig. 5 (c). The slip system is now activated in the upper grain, evidenced by a partial dislocation with Burger's vectors b = (1/6)[1 1 2] nucleated from the interface and slip along the (1 1 −1) plane. After that, dislocation slips collectively in both grain regions accommodate the plastic deformation during the tensile process. The same phenomena has been observed in other cases of Cu bicrystals with asymmetric GB, as shown in S-Fig. 2


Atomistic simulation of tensile deformation behavior of ∑5 tilt grain boundaries in copper bicrystal.

Zhang L, Lu C, Tieu K - Sci Rep (2014)

Snapshots of Cu bicrystal with ∑5 (φ = 11.31°) GB at different deformation stage under free tension boundary condition.Images are colored according to the CNA parameter. Atoms with perfect fcc structures are removed to facilitate viewing of the defective structures. Atoms colored with yellow organize the GB plane and the dislocation core, while the blue atoms represent the stacking fault.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4118255&req=5

f5: Snapshots of Cu bicrystal with ∑5 (φ = 11.31°) GB at different deformation stage under free tension boundary condition.Images are colored according to the CNA parameter. Atoms with perfect fcc structures are removed to facilitate viewing of the defective structures. Atoms colored with yellow organize the GB plane and the dislocation core, while the blue atoms represent the stacking fault.
Mentions: Fig. 5 shows the atomic details of Cu bicrystal with ∑5 (φ = 11.31°) GB at different deformation stages under free boundary condition. Atoms are colored by the CNA parameter and remove the atoms with fcc structures to facilitate the defective structures. The GB region expands and becomes coarsened when deformation occurs. Then, partial dislocations with Burger's vectors b = (1/6)[1 1 2] and b = (1/6)[1 1 −2] are nucleated in the lower grain region, as shown in Fig. 5 (b) at ε = 7.3%. However, unlike the case of ∑5 (φ = 0°) GB, dislocation nucleates into only one crystal lattice when the maximum tensile stress has been reached. This phenomenon can be attributed to the asymmetric GB with different orientation angles in the two lattices. Partial dislocations are nucleated and emitted continuously into the lower grain until the tensile strain reaches ε = 7.6%, as shown in Fig. 5 (c). The slip system is now activated in the upper grain, evidenced by a partial dislocation with Burger's vectors b = (1/6)[1 1 2] nucleated from the interface and slip along the (1 1 −1) plane. After that, dislocation slips collectively in both grain regions accommodate the plastic deformation during the tensile process. The same phenomena has been observed in other cases of Cu bicrystals with asymmetric GB, as shown in S-Fig. 2

Bottom Line: The results show that the ∑5 asymmetric GBs with different inclination angles (φ) are composed of only two structural units corresponding to the two ∑5 symmetric GBs.Tensile deformation is applied under both 'free' and 'constrained' boundary conditions.Simulation results revealed different mechanical properties of the symmetric and asymmetric GBs and indicated that stress state can play an important role in the deformation mechanisms of nanocrystalline materials.

View Article: PubMed Central - PubMed

Affiliation: School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522, Australia.

ABSTRACT
Experiments on polycrystalline metallic samples have indicated that Grain boundary (GB) structure can affect many material properties related to fracture and plasticity. In this study, atomistic simulations are employed to investigate the structures and mechanical behavior of both symmetric and asymmetric ∑5[0 0 1] tilt GBs of copper bicrystal. First, the equilibrium GB structures are generated by molecular statics simulation at 0K. The results show that the ∑5 asymmetric GBs with different inclination angles (φ) are composed of only two structural units corresponding to the two ∑5 symmetric GBs. Molecular dynamics simulations are then conducted to investigate the mechanical response and the underlying deformation mechanisms of bicrystal models with different ∑5 GBs under tension. Tensile deformation is applied under both 'free' and 'constrained' boundary conditions. Simulation results revealed different mechanical properties of the symmetric and asymmetric GBs and indicated that stress state can play an important role in the deformation mechanisms of nanocrystalline materials.

No MeSH data available.


Related in: MedlinePlus