(a) A ⟨110⟩ HREM image of elongated nanodomains in HPT-processed Cu. The domain boundaries are highlighted using black asterisks. (b) Fourier transformation of (a). Two sets of lattice forming a twin relationship are indicated by two rectangles. (c) Inverse Fourier transformation using the (000) and two spots marked “C” in (b). Dislocation cores are marked with black “T” and their slip plane is indicated using a white straight line. (d) Inverse Fourier transformation using the (000) and two spots marked “D” in (b).
A schematic illustration of the dislocation model for the nucleation of deformation twins. (a) a lattice screw dislocation dissociated into two partials and ; (b) the nucleation of a deformation twin via the emission of a twinning partial on a (111) plane adjacent to the stacking fault plane; and (c) the emission of a trailing partial that removes the stacking fault.
The critical stresses , , , and as a function of grain size for in nc Cu.
Variation of the optimum orientation angle with Poisson’s ratio for the screw system.
Parameters for Cu and Al used in our model (see Refs. 39 and 42).
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