COMPARISON BETWEEN SIMULATION CALCULATIONS AND MEASUREMENTS CONCERNING ATHERMAL YIELDING OF PRECIPITATION HARDENING OF CU-CO SINGLE-CRYSTALS

Using a new simulation method, we were able to calculate the yield stresses of flexible dislocation loops necessary for macroscopic gliding. The aim of this contribution is to compare calculations with measurements performed by Nembach et al. and ourselves on Cu-Co single crystals. Knowledge of the coherency strains and stresses of particles as well as their spatial distribution and the distribution function of the particle radii is based on experimental results. We have found certain differences between the well known formulae for the yield stress in the case of precipitation hardening which were derived essentially by Gerold and our simulation. Our calculations, which take into account the flexibility of dislocations, seem to prove that firstly the possibility of overcoming large obstacles in a near screw configuration and secondly unzipping are the predominant effects during plastic deformation in the case of precipitation hardening. Dislocation splitting, which was considered in our simulations, appears to be negligible when using large precipitation arrangements in the calculations.