Flow stress dependence on the grain size in alumina dispersion-strengthened copper with a bimodal grain size distribution

The grain size dependence of flow stress in Cu-2.7 vol.%Al2O3 (15 nm) composite with a bimodal structure was studied. It is shown that the yield strength obeys the Hall-Petch equation when an appropriate value of average grain size based on the rule of mixture is employed. The Hall-Petch constants (sigma(0 epsilon), and k(epsilon)) are proportional to strain as epsilon(0.5). An equation for flow stress as a function of true strain and average grain size is proposed. The effect of alumina nanoparticles on the yield strength is shown to be related to large amounts of dislocations density. (C) 2009 Elsevier B.V. All rights reserved.