Thermoelasticity and plasticity of composites. II. A model system

A theory of the workhardening and Bauschinger effect in two-phase materials, combining dislocation mechanisms with a continuum model, is extended to high volume fraction of the hard phase by using the mean field theory of Paper I [Acta metall.31, 1795 (1983)]. Application of the extended model to available workhardening data for the simple experimental model system of copper with continuous tungsten fibres reveals a novel workhardening contribution: "elastic friction". The contribution arises from the interaction of gliding dislocations with the complex spatially fluctuating pattern of internal stresses induced by the applied stress as a result of elastic heterogeneity. Elastic friction is taken into account in a simple model of the Bauschinger effect, the "modified Orowan-Wilson model", which is substantiated by a new set of experiments on copper-tungsten with large tungsten volume fractions.