On the kinematics of Portevin-Le Chatelier bands:: theoretical and numerical modelling

A model is presented for the description of the Portevin-Le Chatelier (PLC) effect, namely the repetitive plastic yielding that may be observed in metallic alloys for certain ranges of temperature and applied stress or strain rates. The model reflects the underlying microstructural dynamic strain ageing (DSA), i.e.the dynamic interaction between mobile dislocations and diffusing solute atoms. Focus is made on PLC instabilities of Type A, that is PLC bands that nucleate and propagate continuously throughout the tensile specimen as solitary plastic waves. The kinematics of these PLC bands is studied analytically and validated numerically by a Finite Differences integration of the model equations. The characteristics of the PLC bands, that is band speed, band width and band plastic strain, are determined from the space-time fields of plastic activity. The band parameters exhibit very good matching with the theoretical results and order-of-magnitude agreement with the experimental observation of the PLC effect. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.