High temperature plasticity of metals at temperatures larger than fifty percent of melting temperature is, at least for stress ranges of technical interest, explained by thermally activated dislocation movements, where the structure of the material, i.e. distribution and strength of the internal barriers, which act against these movements, are of strong influence on these processes.
The characterization of this structure try transition probabilities of a discrete Markov-chain results in a stochastic model which is able to represent essential and typical features which are characteristic for high temperature plasticity, such as stationary creep, dependence of the internal structure on stress, and temperature or transition times to stationary creep after changes of these loads, in an at least qualitatively satisfactory manner, and which allows for an examination of the effects of assumptions about the deformation mechanisms on the microscale.
The model is derived from the well known assumption that the energy of the flow units obeys a Boltzmann-distribution and that the external stress increases the probability for the passing of the internal barriers in the direction of its action. In contrast to older models of this kind, strain hardening and recovery are included, by assuming that the distribution of the flow-units over the height of the barriers is changed by their movement, which results in hardening, and by a recovery-process which depends on the microstresses and temperature.