Portevin-LeChatelier effect in Al-Mg alloys : influence of obstacles, experiments and modelling

Abstract : Due to their low weight and high mechanical strength Al–Mg alloys provide a large variety of applications as material for lightweight construction. However, the practical benefit is limited due to instabilities and inhomogeneities caused by correlated movement of dislocations during plastic deformation (Portevin–LeChatelier effect, PLC). By addition of unshearable obstacles the formation of dislocation avalanches should be prevented or at least reduced. Uniaxial tension tests at various constant strain rates on the metal matrix composite (MMC) AA5754 with 2 or 5 vol.% Al2O3 particles showed hardly any influence of the particles added. This could be explained by an inhomogeneous distribution of the particles during manufacturing of this MMC. First results of FE simulations using a macroscopic PLC model are presented. The importance of local stress concentrations around the inclusions is emphasized.