Dislocation motion in thin Cu foils: a comparison between computer simulations and experiment

Discrete dislocation dynamics (DD) simulations in conjunction with stereo and in situ straining transmission electronic microscopy (TEM) were used to study dislocation motion in thin Cu foils. Stereo imaging prior to and following in situ tensile straining is utilized to describe the three-dimensional (3D) evolution of dislocation structures with incremental straining and observation by TEM. The initial 3D configuration is used as input for 3D discrete dislocation dynamics simulations, and the final 3D configuration serves to refine and validate the DD simulation, thereby providing a direct quantitative link between experiment and dislocation dynamics modeling. In the present experiment, we observed complex 3D structures of dislocations, with significant outof-plane motion. Computer simulations incorporating the Friedel–Escaig cross-slip mechanism indicate that surface image forces are sufficiently strong to activate out-of-plane motion for screw dislocation segments near the surface. Cross-slip of screw segments and dislocation climb of edge components are shown to be necessary mechanisms for explaining the observed 3D dislocation motion.