Plastic deformation instability in copper alloys

Abstract

A systematic investigation was made of the temperature and velocity conditions for the appearance of stepwise deformation in copper alloys with a high alloying content (the Portevin-Le Chatelier effect) and the deformation mechanics of crystalline materials was analyzed from the viewpoint of an emsemble of dislocations. A mathematical model of the Portevin-Le Chatelier effect was constructed, based on general ideas concerning the behavior of dislocations and their interaction with alloying elements, and from the viewpoint of the theory of oscillations, taking into account the rigidity of the test-piece-machine system. Mechanical tests were performed on copperalloy test pieces in the temperature range 20–400°C. A characteristic feature found for the oscillation modes was that the peak-to-peak value Δσ was independent of ɛ and that there was a plateau with a weak dependence σ(ɛ) at the upper σ level. The dependences of the oscillation period on the temperature and the given plastic deformation velocity were in good agreement with experiment.