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Grain boundary sliding is the process by which grains move to prevent separation at grain boundaries. [1] This process typically occurs on timescales significantly faster than that of mass diffusion (an order of magnitude quicker). Because of this, the rate of grain boundary sliding is typically irrelevant to determining material processes.
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.
Hermann Schlichting studied from 1926 till 1930 mathematics, physics and applied mechanics at the University of Jena, Vienne and Göttingen.In 1930 he wrote his PhD in Göttingen titled Über das ebene Windschattenproblem and also in the same year passed the state examination as teacher for higher mathematics and physics.
A linear variation has been observed between twin thickness, stacking fault energy and grain size, [47] and to a lesser degree, the stress state of the twinning grain (Schmid Factor). [48] The twin thickness saturated once a critical residual dislocations’ density reached the coherent twin-parent crystal boundary. [33] [49]
This reduces the total area of grain boundary and hence the stored energy in the material. Subgrain coarsen shares many features with grain growth. If the sub-structure can be approximated to an array of spherical subgrains of radius R and boundary energy γ s ; the stored energy is uniform; and the force on the boundary is evenly distributed ...
Grain boundary engineering involves manipulating the grain boundary structure and energy to enhance mechanical properties. By controlling the interfacial energy, it is possible to engineer materials with desirable grain boundary characteristics, such as increased interfacial area, higher grain boundary density, or specific grain boundary types ...
The main problem with this theory is that the stored energy due to dislocations is very low (0.1–1 J m −3) while the energy of a grain boundary is quite high (~0.5 J m −3). Calculations based on these values found that the observed nucleation rate was greater than the calculated one by some impossibly large factor (~10 50 ).
A dislocation can ideally move through a crystal until it reaches a grain boundary (the boundary between two crystals). When it reaches a grain boundary, the dislocation will disappear. In that case the whole crystal is sheared a little (needs a reference). There are however different ways in which the movement of a dislocation can be slowed or ...