Real Materials

� Dislocation motion in crystals can occur when a shear stress act across the slip plane. This is illustrated for an edge dislocation.
� The atomic structure is only adjusted in the region of the dislocation line during this motion.

From: Hull, "Introduction to Dislocations," Pergamon (1965)

� This local process that is less energetically expensive than breaking and remaking all the bonds across the slip plane.
� Dislocations can move in crystals at speeds up to the speed of sound, the velocity of elastic waves in the material.
� The Dislocation motion causes plastic deformation of the material. The passage of a single dislocation completely across the slip plane displaces the material above the plane by b with respect to material below the plane.