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(or subboundary structure), in metals, the internal structure of grains characterized by the type, number, and arrangement of lattice defects.
In undeformed metal, the grains consist of blocks (subgrains) that are misoriented relative to one another by angles of the order of minutes of arc; the blocks are separated by subboundaries. The shape, size, and angular misorientation of the subgrains, as well as the length of the subboundaries, are important characteristics of metal substructure. The subgrains contain dislocations, which form arrays or are in a disordered arrangement. The arrangement of dislocations depends on the nature of the material and the “history” of the sample; for example, for small degrees of deformation, dislocations are concentrated in slip planes.
With increasing deformation in such metals as aluminum or iron, the dislocations form complex spatial networks. The type, structure, and arrangement of the dislocation arrays and the density of dislocations are also characteristic of metal substructure.
V. IU. NOVIKOV