A P~enomenological Theory for Plastic Deformation of Polygrystalline Metals*

A consistent phenomenologioal theory is developed for t,he plastic deformation properties of a restricted class of polycrystalline metals. The t,heory introduces the concept of a “hardness state” that can be related to the dislocation “structure” generated in the course of plastic deformation. The conditions t,hat must be satisfied if a plastia equation of state is t,o hold are investigated, and it’ is concluded that it is likely that such an equation of state exists. The implications for current microscopic theories are explored. Some of the current, conclusions that are drawn from experimental data are criticized. In particular, it is shown that the neglect of the influences of anelasticity and of grain boundary sliding has led to incorrect interpretations of grain matrix flow properties. Furthermore. the existence of a steady state deformation regime is challenged.