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The twin thickness saturated once a critical residual dislocations’ density reached the coherent twin-parent crystal boundary. [33] [49] Significant attention has been paid to the crystallography, [50] morphology [51] and macro mechanical effects [52] of deformation twinning.
A twin boundary is a defect that introduces a plane of mirror symmetry in the ordering of a crystal. For example, in cubic close-packed crystals, the stacking sequence of a twin boundary would be ABCABCBACBA. On planes of single crystals, steps between atomically flat terraces can also be regarded as planar defects.
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.
Among the grain boundaries, it is known that the twin boundaries, a special type of low-energy grain boundary has lower interaction energy with dislocation leading to much smaller saturation size of the grain. [13] The cryogenic dynamic plastic deformation creates higher fraction of the twin boundaries compared to the severe plastic deformation.
Twinning is a phenomenon somewhere between a crystallographic defect and a grain boundary. Like a grain boundary, a twin boundary has different crystal orientations on its two sides. But unlike a grain boundary, the orientations are not random, but related in a specific, mirror-image way. Mosaicity is a spread of crystal plane orientations.
Depending upon the relative energies of {111} and {110} facets, the shape can range from an icosahedron (on the left of the figure) with small dents at the five-fold axes (due to the twin boundary energy) when {111} is significantly lower in energy, to (going to the right in the figure) a truncated icosahedron or a Icosidodecahedron when the ...
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The behavior of phase boundaries has been a developing subject of interest and an active interdisciplinary research field, called interface science, for almost two centuries, due partly to phase boundaries naturally arising in many physical processes, such as the capillarity effect, the growth of grain boundaries, the physics of binary alloys ...