SOLUTION HARDENING IN AL-ZN ALLOYS - MEAN JUMP DISTANCE AND ACTIVATION LENGTH OF MOVING DISLOCATIONS

Pulsed nuclear magnetic resonance is 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 (1-21 at%Zn). Spin-lattice relaxation measurements indicate that fluctuations in the quadrupolar field caused by moving dislocations are different compared to those in ultra-pure Al. Moving dislocations advance over a number of solute atoms (order to 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.