Critical Dynamics of Burst Instabilities in the Portevin-Le Châtelier Effect

We investigate the Portevin-Le Châtelier effect (PLC), by compressing Al-Mg alloys in a very large deformation range, and interpret the results from the viewpoint of phase transitions and critical phenomena. The system undergoes two dynamical phase transitions between intermittent (or “jerky”) and “laminar” plastic dynamic phases. Near these two dynamic critical points, the order parameter $1/\tau$ of the PLC effect exhibits large fluctuations, and “critical slowing down” (i.e., the number $\tau$ of bursts, or plastic instabilities, per unit time slows down considerably).