Mesoscale effects on strengthening mechanism in particulate/aluminum metal matrix composites

The thermal and mechanical properties of composites of an 1100 aluminum alloy reinforced with particles of various diborides and carbides have been investigated to determine the role of the mesoscale in altering strengthening mechanisms of discontinuously-reinforced metal matrix composites. Composites were fabricated by hot-isostatically-pressing and swaging, and hot-extrusion. The particle nearest-neighbor distance was developed as a descriptor of the mesoscale. Effects of particle size and size distribution were considered. The nearest-neighbor distance was incorporated into dislocation punching models and correlated with composite subgrain size. Strengthening due to the mismatch between the coefficients of thermal expansion between the matrix and the particle was demonstrated when the nearest-neighbor distance is less than the matrix subgrain size.