Flow stress and work-hardening behaviour of Al-Mg binary alloys

Analysis of the flow stress and work hardening behaviour has been carried out in series of Al-Mg solid solutions between 4 K and 298 K. The results reveal that the yield stress decreases linearly with the temperature and increases approximately linearly with the Mg content in the solution. The thermomechanical and Portevin-Le Chatelier instabilities dominate the flow stress behaviour of alloys at 4 K and 298 K. Dynamics of these instabilities increases with the solute content. It is argued that neither PLC nor adiabatic instabilities contribute to the premature failure of the samples. The work-hardening can be reproduced by the Voce type scaling law in a broad range of temperatures. The mean slip distance obtained from the macroscopic model of work hardening is correlated to the scale of the referenced microstructure; Lambda(min) is interpreted as a transition from cell-like to micro shear band microstructure. The failure is discussed in terms of a critical point in a transition form unsaturated to saturated with defects dislocation substructure. (C) 2014 Elsevier Ltd. All rights reserved.