Critical Dynamics of Burst Instabilities in the PortevinLe Chatelier Effect.pdfVIP

Critical Dynamics of Burst Instabilities in the Portevin-Le Chˆatelier Effect Gianfranco D’Anna1 and Franco Nori2 1 Institut de G´enie Atomique, Ecole Polytechnique F´ed´erale de Lausanne, CH-1015 Lausanne, Switzerland 2 Department of Physics, The University of Michigan, Ann Arbor, Michigan 48109-1120 (February 6, 2008) 1 We investigate the Portevin-Le Chˆatelier effect (PLC), by compressing Al-Mg alloys in a very 0 large deformation range, and interpret the results from the viewpoint of phase transitions and 0 critical phenomena. The system undergoes two dynamical phase transitions between intermittent 2 (or “jerky”) and “laminar” plastic dynamic phases. Near these two dynamic critical points, the c order parameter 1/τ of the PLC effect exhibits large fluctuations, and “critical slowing down” (i.e., e the number τ of bursts, or plastic instabilities, per unit time slows down considerably). D PACS numbers: 62.20.Fe, 81.40.Lm, 83.50.-v 1 The motion of lattice dislocations is the main source interacting dislocation lines or magnetic flux lines, slowly ] of macroscopic plastic deformation in crystalline solids. driven in a disordered landscape with pinning traps, and i c In principle, the motion of a single dislocation in an oth- obeying glassy dissipative dynamics). Weertman [7], and s - erwise perfect crystal is a simple phenomenon. However, more recently Lebyodkin et al. [8], have analyzed the l in a real crystal, many cooperative and core dislocation