Solution hardening in AlZn alloys mean jump distance and activation length of moving dislocations

Abstract

Pulsed nuclear magnetic resonance proved to be a complementary new technique for the study of moving dislocations in AlZn alloys. The NMR technique, in combination with strain-rate change experiments and transmission electron microscopy have been applied to study dislocation dynamics in AlZn alloys (1–2 at.% Zn). Spin-lattice relaxation measurements clearly indicate that fluctuations in the quadrupolar field caused by moving dislocations in AlZn are different compared to those in ultra-pure Al. From the motion induced part of the spin-lattice relaxation rate the mean jump distance of mobile dislocations has been measured as a function of strain. Based on the NMR data and data obtained from strain-rate change experiments it could be concluded that moving dislocations advance over a number of solute atoms (order of 10) as described by Mott-Nabarro's model and interact with forest dislocations as predicted by Friedel's model. The strain rate change experiments confirm the linear additivity of flow stresses and the additivity of inverse activation length.