Creep experiments were conducted on polycrystals deformed within the 5-power-law regime. The dislocation structure consisted of less well-defined sub-grain walls of relatively low misorientation; typically between 0.1 and 0.3º, with a Frank network of dislocations within the sub-grains. The sub-grains were probed from one boundary to another by using convergent-beam electron diffraction. This permitted the determination of any changes in the lattice parameter, which would indicate the presence of internal stresses. Earlier investigations had suggested that internal stresses could be high in the vicinity of so-called hard sub-grain boundaries in both loaded and unloaded specimens, based upon various techniques including X-ray diffraction, stress-dip tests, as well as some preliminary convergent-beam electron diffraction. It was determined here that the lattice parameter remained unchanged at the equilibrium or stress-free value in the interior of the sub-grains and along (within a 1-beam diameter) the sub-grain boundaries.

Dislocation Microstructure and Internal-Stress Measurements by Convergent-Beam Electron Diffraction on Creep-Deformed Cu and Al. M.E.Kassner, M.T.Pérez-Prado, M.Long, K.S.Vecchio Metallurgical and Materials Transactions A, 2002, 33[2], 311-7