Elastic interactions between screw dislocations in iron

The kinetics of elastically interacting screw dislocations has been studied in pure iron strained in situ at low temperature. Annihilating and expanding screw dipoles yield macroscopic activation areas which are substantially smaller than those deduced from conventional mechanical stress, but consistent with theoretical estimates.The kinetics of attractive intersecting screw dislocations indicates that their velocity is determined by the velocity of their most stressed parts. Repulsive screw dislocations with different Burgers vectors can move cooperatively at a surprisingly high velocity, probably on elastic torque interactions and twinning-anti-twinning effects. All these interactions are shown to play an important role in the description of macroscopic mechanical properties in terms of individual dislocation mechanisms.