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[en] From the angular correlation measurements of the positron annihilation radiation on cold rolled, polycrystalline Ni of purity 99.99% and 99.84% the curve-shape parameters S are determined for treating the as-deformed and annealed samples up to a thickness reduction of 90%. The trapping rate of the positrons can be determined for a thickness reduction up to 15 or 18% for the dislocations and for the vacancies as well. Using known relations for the hardening within range 2 the specific trapping rates are estimated for the dislocations, μsub(d) = 2.9 x 10^-15 s^-1, and for the vacancies, μsub(v) = 2.2 x 10^-15 s^-1. Estimated dislocation densities and vacancy concentrations vary between 10⁸ and 10¹¹ cm/cm³ and 10¹⁶ and 10¹⁹ cm^-3, respectively. Both of them show a remarkable dependence on the purity of the samples. Ni of low purity exhibits formation of vacancy clusters after annealing. (author)

[en] By measurements of the peak value of the angular correlation curve of the positron annihilation on cold rolled Ni of purity 99.99, 99.95, and 99.84 % during isothermal annealing at different temperatures information on the annealing of point defects are obtained. From these, Corbett's recovery model for f.c.c. metals modified with respect to plastic deformation can be confirmed for Ni. For pure Ni the recovery stage III is connected with the migration of vacancies, to a large extent in the form of divacancies. On this basis and taking into consideration a possible temperature dependence of the migration energy of monovacancies, Esub(1V)sup(M), the different amounts of Esub(1V)sup(M) and Esub(III), the activation energy of stage III, can be explained. In impure Ni stage III consists of two overlapping substages; the lower is attributed to the release of interstitials from impurities. In the upper substage free vacancies migrate and agglomerate at impurity sites. Stage IV, observed only in impure Ni, is explained by a release of vacancies from impurity traps. The migrating vacancies form small clusters at deeper traps. The process of formation and dissolution of the vacancy clusters is observed. It is shown that this recovery model can explain the characteristic features of the recovery even of the electrical resistivity. (author)