We generalize in this work the constitutive model for silicon crystals of Alexander and Haasen. Strain-rate and temperature dependency of the mechanical behavior of intrinsic crystals are correctly accounted for into stage I of hardening. We show that the steady-state of deformation in stage I is very well reproduced in a wide range of temperature and strain rate. The case of extrinsic crystals containing high levels of dissolved oxygen is examined. The introduction of an effective density of mobile dislocations dependent on the unlocking stress created by oxygen atoms gathered at the dislocation cores is combined to an alteration of the dislocation multiplication rate, due to pinning of the dislocation line by oxygen atoms. This increases the upper yield stress with the bulk oxygen concentration in agreement with experimental observations. The fraction of effectively mobile dislocations is found to decay exponentially with the unlocking stress. Finally, the influence of oxygen migration back onto the dislocations from the bulk on the stress distribution in silicon bars is investigated.
ASJC Scopus subject areas
- Physics and Astronomy(all)