Strain-induced structural changes and chemical reactions—I. Thermomechanical and kinetic models

Strain-induced chemical reactions were observed recently (Nesterenko et al., Appl. Phys. Lett., 1994, 65(24), 3069; Metall. Met. Trans. A, 1995, 26, 2511) in experiments in the shear band in both Ti–Si and Nb–Si mixtures. Reactions can start in the solid state or after melting of at least one component. One of the aims is to find theoretically, whether there are possible macroscopic mechanisms of mechanical intensification of the above and other chemical reactions due to plastic shear in the solid state. Continuum thermodynamical theory of structural changes with an athermal kinetics, which includes martensitic phase transformations, plastic strain-induced chemical reactions and polymorphic transformations, is developed at finite strains. The theory includes kinematics, criterion of structural change and extremum principle for determination of all unknown variable parameters for the case with neglected elastic strains. Thermodynamically consistent kinetic theory of thermally activated structural changes is suggested. The concept of the effective temperature is introduced which takes into account that temperature can vary significantly (on 1000K) during the chemical reactions under consideration. The theory will be applied in Part II of the paper for the description of chemical reactions in the shear band.