On the physics of the Portevin-LeChatelier effect .2. From microscopic to macroscopic behaviour

It was shown in Part 1 that dynamic strain ageing (DSA) of non-interacting dislocations does not give rise to negative strain-rate sensitivities S. To explain unstable plastic flow, the theory is generalized for long-range dislocation interactions. This is achieved by means of a stochastic treatment of dislocation dynamics. Type S instability is associated with a non-equilibrium phase transition to a collective mode of slip which necessitates the combined action of DSA and dislocation interactions according to a positive feedback mechanism. A discussion of the critical phenomena associated with this phase transition is given. Furthermore, experiments are proposed to check the theoretical predictions.