The threshold stress for creep controlled by dislocation-particle interaction

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Abstract
A model based on the dissociation of lattice dislocations into interfacial dislocations, when they enter the matrix-particle interface for climb bypass, is proposed to explain the attractive dislocation-particle interaction during the creep of dispersion-strengthened alloys. This model predicts a threshold stress for creep which depends on the particle radius, the interparticle spacing and the reduction in dislocation self-energy because of dissociation. A minimum energy reduction of about 36% is required through the dissociation to offset the increase in line length energy because of the local climb configuration. There is reasonable agreement between theoretical predictions and experimental data on threshold stresses. The model is also supported by transmission electron microscopy evidence of departure-side pinning and contrast at the matrix-particle interface.