The mode of the serrated deformation is investigated mathematically in framework of the thermoactivation model of unstable plastic deformation in metals at low temperatures. The obtained solutions in the framework of known models, however, do not fully correspond to experimental situation, as the stress oscillations in reality are usually irregular and inhomogeneous. By this reason, additionally, the elastic correlations of neighboring deformation zones were taken into account in the model. Numerical analysis model showed that time dependence of the stress, temperature and plastic deformation rate acquires an irregular stochastic character and is represented as an attractive set of trajectories in the phase space of these variables - "strange attractor".