Investigation of cross-slip events in NaCl crystals by transmission electron microscopy

In primary edge dislocations of NaCl-single crystals plastically deformed at room temperature a relatively high density of long jogs has been observed by transmission electron microscopy. The analysis of such jogs, which in general have been produced by cross-slip of screw dislocations, shows that screw dislocations in NaCl may cross-slip not only on the well-known {001}- and {111}-planes, but in addition on glide planes of higher indices. The shear stresses necessary to move screw dislocations on these planes are estimated to be at maximum about four times of the critical resolved shear stress of the crystals. The influence of abundant possibilities for easy cross-slip of screw dislocations on the plastic behaviour of NaCl crystals is demonstrated by some examples.