A discrete dislocation analysis of the Bauschinger effect in microcrystals

The Bauschinger effect is theoretically investigated in micron-sized crystals using mechanism-based discrete dislocation plasticity. Use is made of constitutive rules that are formulated at the fundamental dislocation level to represent dislocation interactions at short-range, including dislocation multiplication and escape at free surfaces, dislocation intersections, and subsequent dynamic source and obstacle creation and destruction. Various overall responses emerge as a natural outcome to the collective behavior of discrete dislocations, depending on specimen size and initial dislocation source density. At low source density, where the behavior is multiplication controlled, tension/compression asymmetry is often realized and the scatter increases with decreasing specimen size. At sufficiently high source density, hardening mechanisms dominate the behavior and a strong Bauschinger effect is predicted in crystals with heights in the sub-micron range. In this case, the Bauschinger effect is qualitatively correlated with a new, evolving structural measure, which is solely expressible in terms of kinematic quantities.