Analysis of Portevin-Le Chatelier serrations of type Bin Al-Mg

Plastic deformation of solid solutions at elevated temperatures is often accompanied by plastic instabilities due to dynamic strain aging (DSA) and dislocation interaction. The repeated breakaway of dislocations from and their recapture by (clouds of) solute atoms lead to stress serrations and localized strain (deformation bands) in strain controlled tensile tests, known as the Portevin-Le Chatelier (PLC) effect. The present work gives an analysis of stress drops for constant strain rate tensile tests on Al-(1.5-4.5) wt.% Mg in terms of their dependencies on temperature and strain rate for type B deformation bands, the unambiguous classification of which is accomplished by local strain measurements with a multizone laser extensometer. To arrive at a consistent interpretation of the thermal activation behavior of the breakaway of dislocations associated with type B serrations, a dislocation pile-up model is introduced which matches well with these as well as with earlier results on Cu-Al. (C) 2003 Elsevier B.V. All rights reserved.