THE THRESHOLD STRESS FOR CREEP CONTROLLED BY DISLOCATION PARTICLE INTERACTION

A model based on the dissociation of lattice dislocations into interfa cial dislocations, when they enter the matrix-particle interface for c limb bypass, is proposed to explain the attractive dislocation particl e interaction during the creep of dispersion-strengthened alloys. This model predicts a threshold stress for creep which depends on the part icle radius, the interparticle spacing and the reduction in dislocatio n self-energy because of dissociation. A minimum energy reduction of a bout 36% is required through the dissociation to offset the increase i n line length energy because of the local climb configuration. There i s reasonable agreement between theoretical predictions and experimenta l data on threshold stresses. The model is also supported by transmiss ion electron microscopy evidence of departure-side pinning and contras t at the matrix-particle interface.