Creep of a composite with a diffusional creeping matrix

Creep of a composite consisting of diffusional creeping matrix and elastic inclusions has been examined on the basis of micromechanics. A two-dimensional model, in which cylindrical matrix grains and inclusions constitute a composite, is adopted. Grain boundary and interface diffusion and sliding are introduced as deformation processes of plastic character. Internal stresses due to these processes are formulated. The effect of other grains and inclusions are taken into account using the mean field method. The sum of the external stress and these internal stresses drives boundary and interface diffusion and sliding. The macroscopic creep strain is also formulated from the degree of diffusion and sliding. A set of coupled differential equations connecting the rates of diffusion and sliding with the external stress and the strains produced by diffusion and sliding is formulated. It is shown that composite creep eventually terminates if either diffusion or sliding on matrix–inclusion interfaces does not operate, even when the matrix is capable of diffusional creep.