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The lattice resolves the applied stress by grain boundary sliding, resulting in a decrease in the material's yield strength. To understand the mechanism of grain boundary strengthening one must understand the nature of dislocation-dislocation interactions. Dislocations create a stress field around them given by:
In materials science, a grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are two-dimensional defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material.
However, little attention has been given to slip bands within grains (i.e., in the absence of grain boundary interaction). The long-range stress field (i.e., the elastic strain field) around the tip of a stress concentrator, such as a slip band, can be considered a singularity equivalent to that of a crack.
Referring to the paleostress inversion principle, rock masses under stress should exhibit strain at both macroscopic and microscopic scale, while the latter is found at the grain boundaries (interface between crystal grains at the magnitude below 10 2 μm). Strain is revealed from the change in grain size, orientation of grains or migration of ...
Two main mechanisms for altering grain boundaries have been defined. The first is the process by which quartz softens as temperature increases, providing a means for internal stress reduction by migration of dislocations in the crystal lattice, known as dislocation creep. These dislocations concentrate into walls, forming new grain boundaries.
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 ...
Coble creep, or grain-boundary diffusion, is the diffusion of vacancies occurs along grain-boundaries to elongate the grains along the stress axis. Coble creep has a stronger grain-size dependence than Nabarro–Herring creep, and occurs at lower temperatures while remaining temperature dependent.
A stress field is the distribution of internal forces in a body that balance a given set of external forces. Stress fields are widely used in fluid dynamics and materials science . Consider that one can picture the stress fields as the stress created by adding an extra half plane of atoms to a crystal .