The work-hardening of copper-silica v. equilibrium plastic relaxation by secondary dislocations

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Abstract
Continuum plasticity is used to derive a new model for the plastic zone of secondary dislocations (B structure) observed around undeformable particles in a plastically deformed metal matrix. The model is compatible with observations of these dislocations by electron microscopy. The contribution of these dislocations to the flow stress and to the internal stress in the alloy is calculated using a computer model for the dislocation-obstacle problem. The resulting theoretical stress-strain relation is compared with experiment, including information on the Bauschinger effect, the incidence of plastic cavitation, and the dimensional stability of cold-drawn alloy, as well as the conventional stress-strain curve in tension. The overall accuracy of the algebraic equations is about 20%. Finally a discussion is given of the validity of the continuum model for internal stress and the relationship between it and theories which take explicit account of the finite slip line spacing.