Modelling the Bordoni peak†

†Dedicated to Prof. Frank. R. N. Nabarro on the occasion of his 90th birthday, on 7 March 2006.

Abstract

In fcc metals, kink-pair formation in dislocation lines aligned along close-packed lattice directions can give rise to internal friction effects called Bordoni relaxation. The resulting internal friction peak is a superposition of several individual peaks, each with complex features. To study this behaviour, the differential equation describing the movement of dislocation segments by thermally activated kink-pair formation is solved numerically. It is assumed that the kink mobility is high. As a result, the movement is asymmetric, since the backward movement can occur by kink collapse without need of thermal activation. The influence of the external parameters, such as segment length, number of geometrical kinks, internal stress, amplitude and frequency of the applied stress and temperature on the position and shape of the internal friction peaks is studied. When the original configuration is in a bowed out state, the Paré condition is satisfied. Application of an external stress increases the magnitude of internal friction by aligning originally inclined dislocation segments in the direction of the Peierls valleys.

†Dedicated to Prof. Frank. R. N. Nabarro on the occasion of his 90th birthday, on 7 March 2006.

Acknowledgement

Stimulating and helpful discussions with Professor A. Seeger are gratefully acknowledged.

Notes

†Dedicated to Prof. Frank. R. N. Nabarro on the occasion of his 90th birthday, on 7 March 2006.