  Tensile tests have been carried out by deforming polycrystalline samples of
substitutional Al-2.5%Mg alloy at room temperature at a range of strain rates.
The Portevin - Le Chatelier (PLC) effect was observed. From an analysis of the
experimental stress versus time series data we have inferred that the dynamics
of the PLC effect in a local finite time is controlled by a finite number of
degrees of freedom and this effective dimension becomes reduced with increasing
strain.
