Explanation of the discrepancy between the measured and atomistically calculated yield stresses in body-centered cubic metals

摘要

We propose a mesoscopic model that explains the factor of two to threediscrepancy between experimentally measured yield stresses of BCC metals at lowtemperatures and typical Peierls stresses determined by atomistic simulationsof isolated screw dislocations. The model involves a Frank-Read type sourceemitting dislocations that become pure screws at a certain distance from thesource and, owing to their high Peierls stress, control its operation. However,due to the mutual interaction between emitted dislocations the group consistingof both non-screw and screw dislocations can move at an applied stress that isabout a factor of two to three lower than the stress needed for the glide ofindividual screw dislocations.