Dislocations generated by pre-strain dominate the subsequent plastic deformation

Plasticity of sub-micron scale metals is well known to be controlled by dislocation source. Here, we report an in-situ study of how the dislocation structures generated by pre-strain in submicron-sized copper affect the subsequent plastic deformation by conducting nanocompression testing in a transmission electron microscope. The results show that short isolated dislocations first undergo directional intermittent jumping motion along specific glide directions under the applied force. And the jumping frequency and jumping distance of dislocation motion can be determined by the density and strength of obstacles distributed in the crystal. Then, the dislocation wall formed by dislocation pileup and entanglement during pre-strain can effectively pin the mobile dislocation in the early stages of compression, but at high stress levels it will perform overall motion in the form of dislocation avalanches and lead to the strain burst emissions of the material. The in-situ dynamic evolution of dislocation avalanche reveals the emitted dislocations and associated glide planes introduced by pre-strain can preferentially trigger dislocation avalanches of the dislocation wall.