The critical resolved shear stress of single crystals with long-range ordered precipitates calculated by dislocation dynamics simulations

The glide of dislocation pairs (superdislocations) in an order strengthened single crystal (superalloy NIMONIC PE16) is computer simulated, and the critical resolved shear stress is derived. The simulations are based on the local stress equilibrium in one glide plane. The elastic interaction of the dislocations with each other and with themselves is fully allowed for. The mean particle radius, the volume fraction and the energy of the antiphase boundary created by the leading dislocation of a pair are varied. Especially the transition from the peak-aged to the overaged aging state of a crystal is covered by these parameters. In the peak-aged state, the dislocations glide in pairs. Towards the overaged state they become decoupled by the Orowan loops left behind by the leading dislocation. A parameter range for this transition is introduced.