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Effet des impuretés sur les mécanismes de recristallisation du cuivre tréfilé

Abstract : The presence of residual elements in the raw material slows down the recrystallization and changes the annealing behaviour of industrial copper wires resulting from continuous casting. In this context, the work presented in this memory of thesis aimed to study and understand the role of some impurities (sulphur and lead), as well as that of the oxygen introduced before the operation of continuous casting, on the microstructural state after wire -drawing and during the annealing of recrystallization.
The obtained results by neutron diffraction clearly showed a correlation between the stored elastic energy related to the main fibers - the texture develops major <111>//ND and minor <001>//ND fibers - and the rate of impurities present in the material. This is in agreement with the observations in Transmission Electron Microscopy (TEM), which revealed a weaker of dislocations cells size and the presence of isolated dislocations within cells in the material with higher impurities.
A quantitative analysis of the evolution of texture according to the annealing time showed that, the acuity of texture decreases without appearance of new components. The volume fraction of the <001>//ND fiber is stable, while that of the <111>//ND fiber, major component in a drawn state, strongly decreases. We also observed an extension of the incubation phase during the recrystallization for the wires with high content.
At the microscopic scale, the grains related to the <100>//ND fiber nucleate first by cell coalescence close to the highly misoriented grain boundary. The impurities seem to delay the process of recovery necessary to the formation of the nuclei as well as the mobility of the grain boundaries during the recrystallization, certainly by the means of an intergranular segregation.
Concerning the effect of oxygen, the analysis of the deformation substructure in TEM showed a enhanced recovery in the highly oxygen doped material. This dynamic recovery is certainly facilitated by the trapping of the impurities by oxygen. Moreover, the size of oxide particles suggests the possibility of a nucleation mechanism induced by the presence of particles (mechanism PSN).
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Saâd Jakani. Effet des impuretés sur les mécanismes de recristallisation du cuivre tréfilé. Physique [physics]. Université Paris Sud - Paris XI, 2004. Français. ⟨tel-00220406⟩

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