Simulation and observation of dislocation pattern evolution in the early stages of fatigue in a copper single crystal

During cyclic deformation, the early stages of dislocation pattern formation and evolution of a single-slip-oriented copper single crystal were simulated by using the method of discrete dislocation dynamics and observed by using the electron channeling contrast (ECC) technique in a scanning electron microscopy (SEM). Computer simulation results agree rather well with the experimental observations. Hence, some new mechanisms were proposed. Such as in the early stages of cyclic deformation, the formation and evolution of dislocation veins could originate from the matrix walls which are composed by the same sign of dislocations, and a dipole matrix wall could be formed by combining two matrix walls with the opposite signs of dislocations.