Portevin-Le Chatelier effect

Aluminum subjected to smooth mechanical loading does not often deform in a correspondingly smooth manner. Typically it deforms inhomogeneously through the propagation of deformation fronts that slowly traverse the sample. The se are called Portevin-Le Chatelier fronts; what determines their velocity has been somewhat mysterious. We present a phenomenological theory for defo rmation fronts that centers on a nonlocal rate dependence of the flow stres s. In a one-dimensional idealization the equations can be solved exactly, a nd compared directly with experiment. Many significant features of deformat ion fronts are captured, including a well-known transition from hopping to continuous front motion. The phenomenology's predictions are confirmed by o ur experiments.