In situ transmission electron microscopy straining experiments were carried out in pure Fe to investigate the origin of the discontinuity observed at 250K in the temperature variation of the deformation activation parameters. The results show that the motion of screw dislocations was steady at 300K, in agreement with a kink-pair mechanism, but jerky at 110K. This change was attributed to a transition from a kink-pair mechanism to a locking-unlocking mechanism, similar to that observed previously in Ti.

TEM in situ Straining Experiments in Fe at Low Temperature. D.Caillard: Philosophical Magazine Letters, 2009, 89[8], 517-26