Instabilité plastique propagative liée au phénomène Portevin-Le Chatelier dans les alliages aluminium-magnésium

Abstract : Among the manifestations of plastic flow instabilities, one of the most frequently observed is the Portevin-Le Chatelier (PLC) effect. The PLC appears in form of deformation bands propagating a cross the specimen gauge length. It is widely accepted now that the PLC effect originates from the interaction between the mobile dislocations and the diffusing solute atoms, the so-called dynamique strain aging. The aim of this work is to study the characteristics of this plastic instability. The experimental results obtained in this study are mainly concerned with the conditions for the PLC effect occurance, the propagation velocity, the strain and strain rates in the bands. The tensile tests were carried out between -60°C and 100°C, in the Al-Mg alloys, for a wide range of stress and strain rates, in a soft and hard machine respectively. The evolution of incubation deformation Ec for the occurance of the PLC effect, shows that it goes through a transition point in the range of intermediate stress rates, from "normal" behavior to "inverse" behavior. The comparison between the experimental results and the theoretical models, shows that the "standard" model can explain the behavior of Ec at high stress rates. At low stress rates, the inverse behavior of Ec may result from the dynamic strain aging and the reprecipitation of solute atoms. The body of results obtained in this work expand the knowledge about the PLC effect, and help avoid their negative influence on the ductility and the formability of metals
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Sabah Bakir. Instabilité plastique propagative liée au phénomène Portevin-Le Chatelier dans les alliages aluminium-magnésium. Autre. Université Paul Verlaine - Metz, 1995. Français. ⟨NNT : 1995METZ026S⟩. ⟨tel-01777080⟩

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