Effect of reinforcement connectivity on the elasto-plastic behavior of aluminum composites containing sub-micron alumina particles

The mechanical properties of composites consisting of an aluminum matrix with 34 and 37 vol.% sub-micron Al₂O₃ particles were studied in compression for two reinforcement architectures: interconnected and discontinuous. Both the elastic and plastic behaviors of these composites are successfully modeled using a self-consistent approach: the classical self-consistent and the three-phase self-consistent models for the interconnected and discontinuous architectures, respectively. At ambient temperature, an interconnected architecture offers only a modest increase in stiffness and strength over a discontinuous architecture of equal volume fraction. At elevated temperatures (250, 500 and 600 °C), the interconnected reinforcement becomes increasingly more effective at strengthening the composites. However, the relative increase in strength due to interconnectivity can only be exploited at small strains (1-5%) due to the early development of compressive flow instabilities in the interconnected composites. While microstructural damage controls the instability strain of the interconnected composites at ambient temperature, their low strain-hardening coefficient is the main contribution to flow instabilities at elevated temperature.