Study of Plastic Deformation in Aluminium Crystals by Electron Diffraction and Electron Microscopy

Single crystals of highly pure aluminium (99.99%) were plastically deformed and examined by means of electron microscopy and electron diffraction. Surfaces of the deformed crystals produce innumerable slip lines of various slip amounts and deformation bands. The latter greatly affect the diffraction pattern; Laue spots are split, Kikuchi lines are extinguished, and a very high background results. So that, the diffraction pattern from the crystal part containing deformation bands becomes obscured after only a few per cent elongation. While, the effect of crystal imperfections associated with slip lines on the electron diffraction patterns appears to be considerably small, Kikuchi patterns being obtained from laminar-slip regions in a crystal even after 20% elongation. The local distortions expected from the diffraction patterns cannot be explained in terms of the rotations about the [111] axis or in the active slip planes, but rather consist with the local bendings about the [211] axis due to deformation bands. Difference between the state of plastic deformation in the vicinity of the surface and that in the interior of the crystal is conjectured from the difference between the corresponding diffraction patterns. Some considerations on this point are also made.