Physics of severe plastic deformation

The review describes a number of important recent studies in the field of physical fundamentals of severe plastic deformations (SPDs) in metals and alloys and their further systematization. Based on analyses of experimental data and theoretical approaches, we formulate for the first time three fundamental principles and seven characteristic features inherent in SPD processes. SPD physics is entirely based on the postulates of nonequilibrium thermodynamics. A solid under deformation is considered a mechanical dissipative system in which the total energy continuously decreases or dissipates, converting into other, nonmechanical, forms of energy. Within the framework of the proposed nonequilibrium evolutionary thermodynamics, it is possible to describe from a unified standpoint the evolution of the structure of defects for polycrystalline and amorphous metallic materials upon SPD. We note that the process of mechanical alloying of powders should not be completely identified with SPD processes.