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Abstract
In situ transmission electron microscopy straining experiments were carried out in pure Fe to investigate the origin of the discontinuity observed at 250 K in the temperature variation of the deformation activation parameters. The results show that the motion of screw dislocations is steady at 300 K, in agreement with a kink-pair mechanism, but jerky at 110 K. This change has been attributed to a transition from a kink-pair mechanism to a locking–unlocking mechanism, similar to that observed previously in Ti.
Acknowledgements
The author warmly thanks Robin Schaeublin (PSI Willigen) for the loan of the low-temperature straining holder, Jean Le Coze (Ecole des Mines St Etienne) for the elaboration of the Fe ingot, Dominique Lamirault and Jacques Crestou for the preparation of microsamples, and Prof. Jacques Friedel (Orsay University) for his very stimulating comments. This work has been supported by the European Fusion Development Agreement.
Notes
Note
1. As in Fe, screw dislocations in Ti have highly extended cores.