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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]
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.
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.
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
The fracture behavior of materials can be significantly changed by the use of precipitation-based grain boundary design. For example, Meindlhumer et. al. [9] produced a thin film of AlCrN containing a specific distribution of precipitates within the grain boundaries in precipitation-based grain boundary design. The precipitates acted as a ...
There are mainly two types of grain boundary sliding: Rachinger sliding, [2] and Lifshitz sliding. [3] Grain boundary sliding usually occurs as a combination of both types of sliding. Boundary shape often determines the rate and extent of grain boundary sliding. [4] Grain boundary sliding is a motion to prevent intergranular cracks from forming.
This sort of partitioning of solute atoms between the grain boundary and the lattice was predicted by McLean in 1957. [3] Non-equilibrium segregation, first theorized by Westbrook in 1964, [4] occurs as a result of solutes coupling to vacancies which are moving to grain boundary sources or sinks during quenching or application of stress. It can ...
Since the dislocation density increases with plastic deformation, a mechanism for the creation of dislocations must be activated in the material. Three mechanisms for dislocation formation are homogeneous nucleation, grain boundary initiation, and interfaces between the lattice and the surface, precipitates, dispersed phases, or reinforcing fibers.