Propagative instabilities: An experimental view

Propagating bands of localized deformation, such as Lueders bands and Portevin-Le Chatelier bands occur in virtually all alloys when deformed within certain regimes of temperature and strain rate. Such bands have attracted the attention of both theorists and experimentalists over several decades. Early theoretical studies were concerned with phenomenological treatments involving the cause of the instability and microscopic models of the dislocation processes involved. More recently attention has been focused on stability criteria and spatial aspects of band propagation. In view of the renewed theoretical interest in propagative instabilities it is important that the fundamental experimental features of band propagation. In view of the renewed theoretical interest in propagative instabilities it is important that the fundamental experimental features of band propagation be well characterized and understood. In this paper the authors review experimental measurements on deformation bands, with particular emphasis on geometrical aspects of band propagation associated with the Portevin-Le Chatelier effect. They also report new measurements of Portevein-Le Chatelier bands in an Al-Mg-Si alloy.