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Interpretation
W. FRANK, M. RUHLE, and M. SAXLOVA~)It is shown that the vacancy-type Frank dislocation loops on (111) planes observed in neutron-irradiated copper by means of electron microscopy lead to a decrease in the mobility of glide dislocations during plastic deformation which accounts quantitatively for the enhancement of the critical shear stress of copper single crystals caused by neutron irradiation. This follows from the analysis of measurements of the critical shear stress and of electron-microscopical determinations of the loop density in terms of a statistical theory of thermally activated dislocation motion over barriers of different heights. No adjustable parameters enter this analysis.Es wird gezeigt, da13 die in neutronenbestrahltem Kupfer im Elektronenmikroskop sichtbaren Frankschen Leerstellen-Versetzungsringe auf { 11 1 }-Ebenen bei plastischer Verformung zu einer Verminderung der Beweglichkeit der Gleitversetzungen fiihren, durch welche sich die nach Neutronenbestrahlung beobachtete Erhohung der kritischen Schubspanniing von Kupfereinkristallen quantitativ erklaren lafit. Dies geschieht mit Hilfe einer statistischen Theorie der thermisch aktivierten Versetzungsbewegung iiber Hindernisse verschiedener Hohe. I n diese Auswertung gehen keine frei verfiigbaren Parameter ein.
IntroductionMany papers on radiation hardening of neutron-irradiated copper (for references see [l, 2,3]) have been published without too much progress in the theoretical understanding of this phenomenon since Seeger's pioneering work [4, 51. I n Seeger's approach to radiation hardening it was proposed that the increase of the critical shear stress to of copper after neutron irradiation is due to a reduction of the mobility of glide dislocations by "diluted zones" created during irradiation. More specifically, these zones were regarded as dislocation barriers of uniform heights surmountable with the aid of thermal activation and the applied stress.This model, which permits a qualitative description of the temperature dependence of z , , has failed to explain quantitatively tests involving changes of deformation temperature T and strain rate . & [l]. Therefore, Diehl and co-workers [2] extended Seeger's theory with respect to two essential points: They allowed for a height distribution in the radiation-induced dislocation barriers and for the experimentally observed inhomogeneity of the deformation of irradiated copper single crystals [S]. On the experimental side, the correlation between radiation hardening experiments and electron-microscopical observations on neutron-irradiated copper has recently become a powerful tool in clarifying the nature of radiation hardening (see Section 1.2). l ) Visiting Scientist from Mathematical-Physical Faculty of Charles University, Prague.
physica 26jZ
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