Papers by Keyword: SIBM

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Authors: W. Bevis Hutchinson
Abstract: The paper surveys various types of dislocation substructure that are created by plastic deformation in metals. Special reference is made to those substructures that accommodate sharp misorientations as these are of fundamental importance to the nucleation of recrystallisation. Several different mechanisms can give rise to high misorientations; these are discussed in terms of the factors that control them and their relationships to orientation and texture. Different mechanisms for nucleation of recrystallisation may occur depending on the type of substructure, allowing some practical control over the final recrystallised texture.
Authors: Yoshiaki Natori, Kenichi Murakami, Satoshi Arai, Yousuke Kurosaki, Hisashi Mogi, Hotaka Homma
Abstract: Examination of the SIBM mechanism based on the dislocation substructure at the interior of the Goss oriented grain was carried out by changing the grain size prior to the temper rolling. The following results were obtained. 1) SIBM significantly increased Goss orientation during the eminent grain growth with the initial grain sizes from 18 to 55μm. 2) When the initial grain sizes were large, i.e. 37μm and 55μm, the rolling with the reduction beneath the critical value could not promote SIBM, even the normal grain growth could also be hindered. Consequently a proposal was made that the nucleation of the recovery appeared among substructure domains containing sluggish strain. There exists an adequate size of the domain which varies with the change both of the rolling reduction and the initial grain size.
Authors: Joachim Konrad, Stefan Zaefferer, André Schneider
Abstract: It has been shown in literature that the mechanical properties of Fe3Al base alloys are strongly dependent on the heat treatment subsequent to warm rolling. Therefore, the recrystallization behavior of 3 different hot and warm rolled and annealed Fe3Al-based alloys has been investigated. Two of these alloys contain different forms and amounts of second phase particles, while a pure binary alloy was taken as reference. All alloys develop a-(<110>||RD) and g-(<111>||ND) fiber bcc-type rolling and annealing textures, however, the amount of a- and g-fibers vary in dependence of the alloy composition. The current work presents the investigations on the nucleation process during annealing that has been studied by means of high resolution backscatter electron diffraction (EBSD) in the SEM. In particular the occurrence of orientation gradients in the deformed structure and their crystallographic relationship to the formation of new grains was investigated. It was shown, that small particles favor the a-fiber component by hindrance of the growth of new grains. In contrast, large particles lead to particle stimulated nucleation. This weakens the overall texture but does not randomize it since the orientation gradients around particles keep a relationship with the matrix orientation.
Authors: John F. Humphreys
Abstract: The nucleation of recrystallization in deformed and annealed metals is reviewed. The main mechanisms are thought to involve the growth of subgrains by low angle boundary (LAGB) migration in an orientation gradient or the strain induced boundary migration (SIBM) of existing boundaries. Although these mechanisms are reasonably well understood, the details of the dislocation recovery mechanisms which are often required before migration can occur, particularly in metals in which recovery is slow, are poorly understood. Complete experimental investigation of the nucleation event requires a 3-d in-situ technique which will resolve dislocations, and this is not currently available. Although recrystallized grains of orientations not in the deformed structure have been reported, there is as yet no substantial evidence or theory to suggest the creation of new orientations by mechanisms other than annealing twinning. It is concluded that further understanding of the deformed state is required before adequate models of nucleation can be formulated and verified.
Authors: Marcel A.J. Somers, M. Somerday, John F. Humphreys
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