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.