Velocities of Dislocation Groups in Very Thin Neutron-Irradiated Copper Single Crystals Measured by Slip Line Cinematography

Slip line development on very thin flat single crystals of neutron-irradiated Cu (thickness down to only 15 to 20 μm, orientation for single glide, yield region, room temperature) is recorded by high-speed cinematography during tensile deformation. In such very thin crystals glide dislocations on the slip plane must be arranged in a rather simple way. Drops in tensile load occuring during initiation of single slip lines at the Lüders band front indicate that in the beginning of a slip line development dislocation groups traverse the whole glide plane in very short times. Evaluating the data measured for the slip line growth vs ≧ 10 cm/s is found for screw dislocations and ve ≧ vs for edge dislocations. For later stages on thin crystals and for all stages on thick crystals (≧ several 100 μm) slip line development is much slower and slip lines show many cross slip events which then appear to control the mean velocity of the dislocations.