Plastic instabilities and dislocation densities during plastic deformation in Al–Mg alloys

Plastic deformation of Al–Mg alloys were investigated by analyzing the stress–strain curves obtained in uniaxial compression tests at constant loading rate. Experimental results have shown the well-known phenomenon of plastic instabilities – the Portevin–Le Chatelier effect – in these solid solution alloys. Using the characteristics of plastic instabilities – the local stress increment, Δσ, – dislocation densities were calculated and compared with those determined by considering the global strain hardening. The influence of the increasing Mg concentration on the multiplication and the annihilation of dislocations, as well as on the development of the mobile and immobile dislocation densities was also analyzed.