Using transmission electron microscopy a systematic study of the dislocation microstructure after cyclic deformation of nickel single crystals was undertaken in order to describe quantitatively the influence of deformation temperature on microstructural parameters. The frequency distributions of the heights and lengths of edge dislocation dipoles were measured in the walls and channels of persistent slip bands and in the matrix bundles after deformation at 77, 293, 600 and 750 K. The mean dipole height as well as the dipole annihilation distance and the critical dipole height were found to increase with increasing temperature while the dislocation density decreased. The dipole heights turned out to be independent of the position of the dipoles in the dislocation substructure. The results are discussed with regard to the development of microstructure‐based models of cyclic deformation and fatigue dislocation patterning.
Mobile dislocations are introduced into samples of GaP:S and GaAs:Zn by uniaxial compression (ϵpl = 1 to 5%) at 820 K. As TEM investigation shows, the resulting irregular dislocation network shows a tendency to rearrangement after a long term (N ≈︁ 7 × 108) ultrasonic treatment at a frequency of 100 kHz and a temperature between 400 and 600 K. The mechanical damping and modulus defect are in good agreement with the Granato‐Lücke theory. Under fatigue conditions applied here, the dislocation structure can be changed by comparably low ultrasound stresses (σ ≈︁ 25 to 56 MPa) at low temperatures.
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