Irreversible thermodynamics modelling of plastic deformation of metals

Irreversible thermodynamics is employed to describe plastic deformation of metallic single crystals and coarse grained polycrystals. Dislocations are assumed to increase the crystal entropy via processes of dislocation generation, glide and annihilation. It is postulated that the entropy progresses according to the relationship dS/d gamma=kappa(C/ T)d tau/d gamma, where S is the entropy of the deformed metal, gamma is the shear strain, kappa is a scaling factor measuring the average distance between dislocations, C is a material dependent constant, T is the absolute temperature and tau is the shear stress. A succinct expression for dislocation evolution is obtained; it is qualitatively similar to that proposed by Kocks and Mecking ( Prog. Mater. Sci., 2003, 48, 171-273) on a phenomenological basis. The model is applied to the description of the deformation behaviour of Cu and Al with good results.