Influence de l'anisotropie structurale sur la plasticité nonuniforme de type Portevin — Le Chatelier

Abstract

The mechanical characteristics of plastic deformation of commercial Al-base alloys 3004 and 5052 have been investigated in some detail. Anisotropy results are reported and the most important parameters of nonuniform deformation of the Poitevin — Le Chatelier effect are re-examined. Through uniaxial tensile tests, along three orientations with respect to the rolling direction, the amplitude of serrated yielding, the reloading time and the homogeneous strain between successive bands, the strain rate sensitivity and the critical strain for the onset of jerky flow have been studied and discussed as a function of strain, reloading time, and strain rate at room temperature. Also discussed are the influences of structural anisotropy and chemical composition on the nonuniform plastic deformation. It is shown that, except for the case of the critical strain, the structural anisotropy of the rolling texture of these materials doesn't have a substantial influence on the features of the nonuniform plastic flow. These materials present a spatial isotropy with respect to the mechanical behavior, and the strain rate sensitivity remains unchanged along three directions of tensile test and seems to reach an average value of saturation as a function of strain. In a large domain of explored strain rates, the critical strain dependence on strain rate for the onset of jerky flow presents two distinct behaviors: normal for Al-3004 and inverse for Al-5052. The spatial profile of hardness allows the qualitative identification of the zones where the plastic deformation is localised along the specimen.