Hardening of metal-ceramic composites due to coefficients of thermal expansion mismatch

The difference in coefficients of thermal expansion (CTE) between reinforcememt and matrix produces nonconventional strengthening mechanisms due to an increase in dislocation density and a decrease in the subgrain size. Both mechanisms together with the thermal residual stress due to CTE mismatch and elastic inhomogeneity can account for the dramatic increment in composite yield stress under some thermomechanical treatment conditions. The current paper is devoted to the study of the first elastoplastic transition by continuum mechanics when the material is cooled from the fabrication temperature. An iterative generalized Eshelby model is used to calculate the elastoplastic solution. The matrix plastic yielding is localized in the reinforcement vicinities where an increase in dislocation density is considered. The plastic work due to CTE mismatch and cooling give some hints about dislocation density increment and consequent strengthening. The interaction between inclusions is described by a mean field theory like the Mori-Tanaka method.