Diffusion-induced stresses: theory and applications

Recent experiments indicated that stresses induced by atomic interdiffusion in solids can not only result in the macro-distortion of materials, but also form some peculiar micro-structures in the materials. However, traditional theories of chemical diffusion in solid states can not describe the relation of diffusion fluxes and diffusion-induced stresses because the subject matter of traditional theories is the diffusing atom or atomic flux, not the volume unit in the interdiffusion field. For this reason, the concept of 'flow point' in the interdifftision field is proposed and the methods of fluid mechanics are applied to describe interdiffusion growth of solid phase. Two types of phase growth, i.e. volume and interface growths, are mathematically defined and the diffusion-induced stresses and strains related to the two types of growth respectively are elucidated. Various phenomena of diffusion-induced stresses have been explained successfully by this theory of interdiffusion growth and stresses. Especially, the mechanism of periodic layer formation during solid state reactions has been analyzed as a representative phenomenon of diffusion-induced stresses.