The Experts below are selected from a list of 2370 Experts worldwide ranked by ideXlab platform
Anna Serra - One of the best experts on this subject based on the ideXlab platform.
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Disconnection Motion in Low- and High-Angle Symmetrical Tilt Grain Boundaries in Hcp Metal
Materials Science Forum, 2013Co-Authors: R.c. Pond, J.p. Hirth, H.a. Khater, Anna SerraAbstract:The structure of disconnections in symmetrical low- and high-angle [0001] tilt boundaries in an Hcp Metal are studied using atomic-scale simulation. Applied engineering strains cause such defects to move conservatively along the boundaries, producing coupled shear and migration. The Peierls stresses causing such motion are found to decrease precipitously through the transition from low- to high-angle boundaries. The reason underlying this behaviour is discussed.
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Interaction of a moving {101-2} twin boundary with perfect dislocations and loops in an Hcp Metal
Philosophical Magazine, 2010Co-Authors: Anna Serra, D J BaconAbstract:Atomic-scale computer simulation is used to investigate the interaction of a moving {101-2} twin boundary in an Hcp Metal with either a straight 1/3(0001) dislocation lying perpendicular to the direction of twinning shear or a periodic row of perfect dislocation loops. The screw dislocation does not decompose in the moving interface and has no effect on its motion. The 60° mixed dislocation is attracted by the boundary and decomposes into twinning dislocations and a disconnection (an interfacial defect with both step and dislocation character): the sign of the crystal dislocation determines the form of the disconnection and thus its effect on twin boundary motion. Boundary reactions with crystal dislocations are likely to be important for assisting the twinning process. Loops with Burgers vector, b, parallel to the interface are reformed in the other crystal after the twin boundary has passed through. The boundary attracts both interstitial and vacancy dislocation loops with inclined b but is not transparent to them, for the complete loop is swept along its glide prism by the moving interface. Depending on its nature, a loop either retains its structure in its parent crystal or is absorbed in the interface. The decomposition product in the latter case is consistent with the reactions of straight dislocations. The results indicate that twinning is efficient at sweeping loops from the microstructure when their density is low and is suppressed by loops when their density is high.
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Interaction of a moving { } twin boundary with perfect dislocations and loops in a Hcp Metal
Philosophical Magazine, 2010Co-Authors: Anna Serra, David BaconAbstract:Atomic-scale computer simulation is used to investigate the interaction of a moving {1012} twin boundary in a Hcp Metal with either a straight 1/3 dislocation lying perpendicular to the direction of twinning shear or a periodic row of perfect dislocation loops. The screw dislocation does not decompose in the moving interface and has no effect on its motion. The 60°-mixed dislocation is attracted by the boundary and decomposes into twinning dislocations and a disconnection (an interfacial defect with both step and dislocation character): the sign of the crystal dislocation determines the form of the disconnection and, thus, its effect on twin boundary motion. Boundary reactions with crystal dislocations are likely to be important for assisting the twinning process. Loops with Burgers vector, b , parallel to the interface are reformed in the other crystal after the twin boundary has passed through. The boundary attracts both interstitial and vacancy dislocation loops with inclined b , but is not transparent...
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interaction of a moving twin boundary with perfect dislocations and loops in a Hcp Metal
Philosophical Magazine, 2010Co-Authors: Anna Serra, D J BaconAbstract:Atomic-scale computer simulation is used to investigate the interaction of a moving {1012} twin boundary in a Hcp Metal with either a straight 1/3 dislocation lying perpendicular to the direction of twinning shear or a periodic row of perfect dislocation loops. The screw dislocation does not decompose in the moving interface and has no effect on its motion. The 60°-mixed dislocation is attracted by the boundary and decomposes into twinning dislocations and a disconnection (an interfacial defect with both step and dislocation character): the sign of the crystal dislocation determines the form of the disconnection and, thus, its effect on twin boundary motion. Boundary reactions with crystal dislocations are likely to be important for assisting the twinning process. Loops with Burgers vector, b , parallel to the interface are reformed in the other crystal after the twin boundary has passed through. The boundary attracts both interstitial and vacancy dislocation loops with inclined b , but is not transparent...
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A new model for {1012} twin growth in Hcp Metals
Philosophical Magazine A, 1996Co-Authors: Anna Serra, David BaconAbstract:Abstract Computer simulation has been used to study the interaction of a perfect, basal dislocation with a {1012} twin boundary in a Hcp Metal for the situation where the 1/3{1120} Burgers vector is inclined at 60° to the interface. It is found that slip is not transferred from one crystal to the other with a residual dislocation left at the interface. Instead, the matrix dislocation decomposes into interfacial defects. We show that as a result of this decomposition the matrix dislocation becomes a new source of twinning dislocations that produce twin growth when the appropriate stress is applied to the crystal. The mechanism described does not require twinning dislocations to multiply by a pole process.
Yan Zhang - One of the best experts on this subject based on the ideXlab platform.
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the formation and migration of the vacancies in Hcp Metal mg
Radiation Effects and Defects in Solids, 2009Co-Authors: Jian-min Zhang, Yan ZhangAbstract:The formation and migration energies of the mono- and di-vacancy in Mg crystal have been calculated using the modified analytical embedded atom method. The results show that, for mono-vacancy, the migration in the basal plane is slightly preferred to the migration out of the basal plane. For di-vacancy, the 1NN and 2NN configurations are not only easier to form but also more stable than the other configurations. The preferred migration mechanisms of the 1NN and 2NN di-vacancy are either invariable 1NN or 2NN configurations during migration in the basal plane or exchange 1NN for 2NN or 2NN for 1NN for migration out of the basal plane. These two-jump migration mechanisms of the di-vacancy, especially the former, are still preferred over the migration of the mono-vacancy. It is concluded that the greater the number of resting vicinity vacancies, the easier the migrating vacancy moves.
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Dependence of the strain energies on grain orientations in Hcp Metal films
Applied Surface Science, 2006Co-Authors: Jian-min Zhang, Yan ZhangAbstract:Abstract A thin polycrystalline film bonded tightly to a thick substrate of different thermal expansion coefficients will experience thermal strain when the temperature is changed. Calculations of the strain energies for grains having various crystallographic orientations ( h k l ) relative to the film surface were made for a polycrystalline film composed of the close-packed hexagonal (Hcp) Metal Be, Cd, Co, Hf, Mg, Re, Ru, Sc, Ti, Y, Zr and Zn, respectively. From strain energy minimization, the (0 0 1), (0 1 3), (0 4 5), (1 2 3), (2 5 8), (0 5 7), (0 3 5), (0 5 7), (0 1 0), (5 5 8), (1 4 7) and (0 0 1) textures should be favorable in Be, Cd, Co, Hf, Mg, Re, Ru, Sc, Ti, Y, Zr and Zn film, respectively.
D J Bacon - One of the best experts on this subject based on the ideXlab platform.
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Interaction of a moving {101-2} twin boundary with perfect dislocations and loops in an Hcp Metal
Philosophical Magazine, 2010Co-Authors: Anna Serra, D J BaconAbstract:Atomic-scale computer simulation is used to investigate the interaction of a moving {101-2} twin boundary in an Hcp Metal with either a straight 1/3(0001) dislocation lying perpendicular to the direction of twinning shear or a periodic row of perfect dislocation loops. The screw dislocation does not decompose in the moving interface and has no effect on its motion. The 60° mixed dislocation is attracted by the boundary and decomposes into twinning dislocations and a disconnection (an interfacial defect with both step and dislocation character): the sign of the crystal dislocation determines the form of the disconnection and thus its effect on twin boundary motion. Boundary reactions with crystal dislocations are likely to be important for assisting the twinning process. Loops with Burgers vector, b, parallel to the interface are reformed in the other crystal after the twin boundary has passed through. The boundary attracts both interstitial and vacancy dislocation loops with inclined b but is not transparent to them, for the complete loop is swept along its glide prism by the moving interface. Depending on its nature, a loop either retains its structure in its parent crystal or is absorbed in the interface. The decomposition product in the latter case is consistent with the reactions of straight dislocations. The results indicate that twinning is efficient at sweeping loops from the microstructure when their density is low and is suppressed by loops when their density is high.
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interaction of a moving twin boundary with perfect dislocations and loops in a Hcp Metal
Philosophical Magazine, 2010Co-Authors: Anna Serra, D J BaconAbstract:Atomic-scale computer simulation is used to investigate the interaction of a moving {1012} twin boundary in a Hcp Metal with either a straight 1/3 dislocation lying perpendicular to the direction of twinning shear or a periodic row of perfect dislocation loops. The screw dislocation does not decompose in the moving interface and has no effect on its motion. The 60°-mixed dislocation is attracted by the boundary and decomposes into twinning dislocations and a disconnection (an interfacial defect with both step and dislocation character): the sign of the crystal dislocation determines the form of the disconnection and, thus, its effect on twin boundary motion. Boundary reactions with crystal dislocations are likely to be important for assisting the twinning process. Loops with Burgers vector, b , parallel to the interface are reformed in the other crystal after the twin boundary has passed through. The boundary attracts both interstitial and vacancy dislocation loops with inclined b , but is not transparent...
David Bacon - One of the best experts on this subject based on the ideXlab platform.
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Interaction of a moving { } twin boundary with perfect dislocations and loops in a Hcp Metal
Philosophical Magazine, 2010Co-Authors: Anna Serra, David BaconAbstract:Atomic-scale computer simulation is used to investigate the interaction of a moving {1012} twin boundary in a Hcp Metal with either a straight 1/3 dislocation lying perpendicular to the direction of twinning shear or a periodic row of perfect dislocation loops. The screw dislocation does not decompose in the moving interface and has no effect on its motion. The 60°-mixed dislocation is attracted by the boundary and decomposes into twinning dislocations and a disconnection (an interfacial defect with both step and dislocation character): the sign of the crystal dislocation determines the form of the disconnection and, thus, its effect on twin boundary motion. Boundary reactions with crystal dislocations are likely to be important for assisting the twinning process. Loops with Burgers vector, b , parallel to the interface are reformed in the other crystal after the twin boundary has passed through. The boundary attracts both interstitial and vacancy dislocation loops with inclined b , but is not transparent...
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A new model for {1012} twin growth in Hcp Metals
Philosophical Magazine A, 1996Co-Authors: Anna Serra, David BaconAbstract:Abstract Computer simulation has been used to study the interaction of a perfect, basal dislocation with a {1012} twin boundary in a Hcp Metal for the situation where the 1/3{1120} Burgers vector is inclined at 60° to the interface. It is found that slip is not transferred from one crystal to the other with a residual dislocation left at the interface. Instead, the matrix dislocation decomposes into interfacial defects. We show that as a result of this decomposition the matrix dislocation becomes a new source of twinning dislocations that produce twin growth when the appropriate stress is applied to the crystal. The mechanism described does not require twinning dislocations to multiply by a pole process.
Jian-min Zhang - One of the best experts on this subject based on the ideXlab platform.
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the formation and migration of the vacancies in Hcp Metal mg
Radiation Effects and Defects in Solids, 2009Co-Authors: Jian-min Zhang, Yan ZhangAbstract:The formation and migration energies of the mono- and di-vacancy in Mg crystal have been calculated using the modified analytical embedded atom method. The results show that, for mono-vacancy, the migration in the basal plane is slightly preferred to the migration out of the basal plane. For di-vacancy, the 1NN and 2NN configurations are not only easier to form but also more stable than the other configurations. The preferred migration mechanisms of the 1NN and 2NN di-vacancy are either invariable 1NN or 2NN configurations during migration in the basal plane or exchange 1NN for 2NN or 2NN for 1NN for migration out of the basal plane. These two-jump migration mechanisms of the di-vacancy, especially the former, are still preferred over the migration of the mono-vacancy. It is concluded that the greater the number of resting vicinity vacancies, the easier the migrating vacancy moves.
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Dependence of the strain energies on grain orientations in Hcp Metal films
Applied Surface Science, 2006Co-Authors: Jian-min Zhang, Yan ZhangAbstract:Abstract A thin polycrystalline film bonded tightly to a thick substrate of different thermal expansion coefficients will experience thermal strain when the temperature is changed. Calculations of the strain energies for grains having various crystallographic orientations ( h k l ) relative to the film surface were made for a polycrystalline film composed of the close-packed hexagonal (Hcp) Metal Be, Cd, Co, Hf, Mg, Re, Ru, Sc, Ti, Y, Zr and Zn, respectively. From strain energy minimization, the (0 0 1), (0 1 3), (0 4 5), (1 2 3), (2 5 8), (0 5 7), (0 3 5), (0 5 7), (0 1 0), (5 5 8), (1 4 7) and (0 0 1) textures should be favorable in Be, Cd, Co, Hf, Mg, Re, Ru, Sc, Ti, Y, Zr and Zn film, respectively.
