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As such, substitutional solute atoms do not interact with the shear stress fields characteristic of screw dislocations. Conversely, in interstitial solid solutions, solute atoms cause a tetragonal distortion, generating a shear field that can interact with edge, screw, and mixed dislocations.
The crystal structures of solute and solvent must be similar. Complete solubility occurs when the solvent and solute have the same valency. [2] A metal is more likely to dissolve a metal of higher valency, than vice versa. [1] [3] [4] The solute and solvent should have similar electronegativity.
In metal alloys with substitutional solute elements, such as aluminum-magnesium alloys, dynamic strain aging leads to negative strain rate sensitivity which causes instability in plastic flow. [4] The diffusion of solute elements around a dislocation can be modeled based on the energy required to move a solute atom across the slip plane of the ...
Dislocations may be pinned due to stress field interactions with other dislocations and solute particles, creating physical barriers from second phase precipitates forming along grain boundaries. There are five main strengthening mechanisms for metals, each is a method to prevent dislocation motion and propagation, or make it energetically ...
Dislocations are linear defects, around which the atoms of the crystal lattice are misaligned. [14] There are two basic types of dislocations, the edge dislocation and the screw dislocation. "Mixed" dislocations, combining aspects of both types, are also common. An edge dislocation is shown. The dislocation line is presented in blue, the ...
When the dislocation velocity is not too high (or the creep rate is not too high), the solute atom can follow the dislocations, and thus introduce "drag" on the dislocation motion. A high diffusivity decreases the drag, and greater misfit parameters lead to greater binding energies between the solute atom and the dislocation, resulting in an ...
A screw dislocation can be visualized by cutting a crystal along a plane and slipping one half across the other by a lattice vector, the halves fitting back together without leaving a defect. If the cut only goes part way through the crystal, and then slipped, the boundary of the cut is a screw dislocation.
where is the diffusivity of the solute atom in the host material, is the atomic volume, is the velocity of the dislocation, is the diffusion flux density, and is the solute concentration. [5] The existence of the Cottrell atmosphere and the effects of viscous drag have been proven to be important in high temperature deformation at intermediate ...