Portevin–Le Chatelier effect

The Portevin–Le Chatelier effect describes a serrated stress-strain curve, which some materiels exhibit as they undergo plastic deformation.

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This effect occurs, when solute atoms (e.g C in steels) have sufficient mobility and thus can segregate at a dislocation core. Because these positions are energetically favorable, these atoms lock the dislocation i.e. a larger force (and therefore stress) is necessary to move the dislocation. As the dislocation is torn away from the solute atoms, the stress in the stress-strain curve drops. Since this process can happen several time, it leads to serrations in the curve.