Résumé. -La résonance magnétique nucléaire est appliquée à l'étude de la variation de la vitesse des dislocations avec la contrainte de compression appliquée dans des cristaux d'halogénures alcalins. T lp a été mesurée en fonction du taux s de la déformation plastique. La route moyenne des dislocations mobiles a été déterminée. Nous indiquons les résultats des expériences sur de différents noyaux, sur de différentes orientations des cristaux et sur des températures différentes.Abstract. -Dislocations moving at various velocities in deforming alkali halide single crystals were studied using the technique of pulsed nuclear magnetic resonance. The spin lattice relaxation rate in the rotating frame is measured as a function of the plastic deformation rate 6. From this the mean free path of mobile dislocations can be determined. The results for different resonant nuclei, different crystal orientations with respect to the crystal axis and different temperatures are presented.

Nuclear magnetic resonance pulse techniques are applied in situ to investigate the dynamics of mobile dislocations during creep deformation of NaCl single crystals. 23Na spin-lattice relaxation rates were measured in the rotating frame (T1ρ) during compression creep of single crystals of NaCl along the [110] direction at 478 K and 20 MPa. The relaxation rates are evaluated from the spin-echo height following a π/2 locking and 64° pulse sequence. The mean jump distance of the mobile dislocations, evaluated from the ratio of the signal heights without deformation and during creep, decreased with time/strain reaching a constant value at the onset of the steady-state creep regime. The results are compared with the dislocation-dislocation spacing, the subgrain size, and the jump distance predicted from creep models.

Nuclear magnetic resonance pulse techniques were used in situ during creep of single crystals of NaCl to evaluate the contribution of mobile dislocations to spin relaxation. 'jNa spin-lattice relaxation rates were measured in the rotating frame (TIP) during compression creep of single crystals of NaCl along the [110] direction at 473 K at an applied stress of 20 MPa. The relaxation rates were evaluated from the spin-echo height following r/2, locking, and 64" pulse sequence. We describe here the experimental setup and methodology in evaluating the dislocation jump distance from NMR-creep experiments. The height of the free induction decay decreased as soon as the load was applied followed by a gradual increase until the steady state was reached, at which point a saturation value was observed corresponding to the constant steady-state creep rate. The mean jump distance of the mobile dislocations, evaluated from the ratio of the signal heights without deformation and during creep, decreased with time/strain, reaching a constant value during the steady-state creep regime. The results are compared with the dislocation-dislocation spacing, subgrain size, as well as the jump distance predicted from creep models. [

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