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 (σ0ɛ and kɛ) are proportional to strain as ɛ0.5. 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.