Dislocation Multiplication from the Frank-Read Source in Atomic Models

Dislocation multiplication from the Frank Read source is investigated in aluminum by applying atomic models. To express the dislocation bow-out motion and dislocation loop formation, we introduce cylindrical holes as a strong pinning point to the dislocation-bowing segment. The critical configuration for dislocation bow-out in atomic models exhibits an oval shape, which agrees well with the results obtained by the line tension model. The critical shear stress for the dislocation bow-out in atomic models continuously increases with decreasing length L of the Frank Read source (even at the nanometer scale). This is expressed by the function L-1 lnL, which is obtained by a continuum model based on elasticity theory. The critical shear stresses for the Frank Read source are compared with those for grain boundary dislocation sources, as well as the ideal shear strength.