Effect of texture on grain boundary misorientation distributions in polycrystalline high temperature superconductors

1996 ◽  
Vol 68 (5) ◽  
pp. 711-713 ◽  
Author(s):  
A. Goyal ◽  
E. D. Specht ◽  
D. M. Kroeger ◽  
T. A. Mason
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
High Temperature Superconductors ◽  
Boundary Misorientation ◽  
Grain Boundary Misorientation

Measurement of solute segregation to grain boundaries in the AEM: A review

1988 ◽  
Vol 46 ◽  
pp. 606-607
Author(s):  
D. B. Williams ◽  
A. D. Romig
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Boundary Misorientation ◽  
Collector Plate ◽  
Segregation Process ◽  
Grain Boundary Misorientation ◽  
Structure Boundary ◽  
Equilibrium Segregation

The segregation of solute or imparity elements to grain boundaries can occur by three well-defined processes. The first is Gibbsian segregation in which an element of minimal matrix solubility confines itself to a monolayer at the grain boundary. Classical examples include Bi in Cu and S or P in Fe. The second process involves the depletion of excess matrix solute by volume diffusion to the boundary. In the boundary, the solute atoms diffuse rapidly to precipitates, causing them to grow by the ‘collector-plate mechanism.’ Such grain boundary diffusion is thought to initiate “Diffusion-Induced Grain Boundary Migration,” (DIGM). This process has been proposed as the origin of eutectoid transformations or discontinuous grain boundary reactions. The third segregation process is non-equilibrium segregation which result in a solute build-up around the boundary because of solute-vacancy interactions.All of these segregation phenomena usually occur on a sub-micron scale and are often affected by the nature of the grain boundary (misorientation, defect structure, boundary plane).

scholarly journals The Effects of Grain Boundary Misorientation on the Mechanical Properties and Mechanism of Plastic Deformation of Ni/Ni3Al: A Molecular Dynamics Study

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5715
Author(s):  
Jun Ding ◽  
Sheng-Lai Zhang ◽  
Quan Tong ◽  
Lu-Sheng Wang ◽  
Xia Huang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Grain Boundary ◽  
Misorientation Angle ◽  
Interfacial Energy ◽  
Stacking Faults ◽  
Boundary Misorientation ◽  
Grain Boundary Misorientation ◽  
Mechanisms Of Plastic Deformation

The effects of grain boundary misorientation angle (θ) on mechanical properties and the mechanism of plastic deformation of the Ni/Ni3Al interface under tensile loading were investigated using molecular dynamics simulations. The results show that the space lattice arrangement at the interface is dependent on grain boundary misorientations, while the interfacial energy is dependent on the arrangement. The interfacial energy varies in a W pattern as the grain boundary misorientation increases from 0° to 90°. Specifically, the interfacial energy first decreases and then increases in both segments of 0–60° and 60–90°. The yield strength, elastic modulus, and mean flow stress decrease as the interfacial energy increases. The mechanism of plastic deformation varies as the grain boundary misorientation angle (θ) increases from 0° to 90°. When θ = 0°, the microscopic plastic deformation mechanisms of the Ni and Ni3Al layers are both dominated by stacking faults induced by Shockley dislocations. When θ = 30°, 60°, and 80°, the mechanisms of plastic deformation of the Ni and Ni3Al layers are the decomposition of stacking faults into twin grain boundaries caused by extended dislocations and the proliferation of stacking faults, respectively. When θ = 90°, the mechanisms of plastic deformation of both the Ni and Ni3Al layers are dominated by twinning area growth resulting from extended dislocations.

Site Exchange in High Temperature Superconductors

1987 ◽  
Vol 99 ◽  
Author(s):  
D. J. Li ◽  
H. Shibahara ◽  
J. P. Zhang ◽  
L. D. Marks
Keyword(s):  
Heavy Metals ◽  
High Temperature ◽  
Grain Boundary ◽  
High Temperature Superconductors ◽  
Planar Defects ◽  
Electron Microscopical Analysis ◽  
Site Exchange ◽  
Copper Sites ◽  
Electron Microscopical ◽  
Brown Powder

ABSTRACTElectron microscopical analysis of brown powders of composition YBa2Cu3O6.5 produced by oil quenching and conventionally produced orthorhombic GdBa2Cu3O7-δ show in both cases clear evidence for site exchange both between the different heavy metals and the heavy metals and the copper sites. For instance, the brown powder is a mixture of phases which are based upon two trigonal phases, both with a=0.536 and c=0.666 nm, one with the Y atoms stacked on the (111) planes of the parent perovskite structure and the second where the Y atoms of this structure have interchanged with one of the copper sites. The GdBa2Cu3O7-δ, material shows numerous planar defects on (001) planes which can be understood as copper rich regions with additional copper planes in the Ba or Gd sites. These results, together with earlier reports of order-disorder in YBa2Cu3O7-δ, strongly indicate that there exist ordering energies in these materials which may be important with respect to the current indications of the important of grain boundary phases in degrading the performance of some superconductors.

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