Influence of particulate B4C with high weight fraction on microstructure and mechanical behavior of an Al-based metal matrix composite

The current study explores Al-Zn-Mg alloy reinforced with a high weight fraction of B 4 C particles as a model system to elucidate the relationship between the microstructure and mechanical behavior of submicron-grained, precipitation strengthened Al-based metal matrix composites (MMCs). Our results indicate that the incorporation of high weight fraction of B 4 C reinforcement particles can lead to a high dislocation density within the Al grains. Under identical aging condition, this results in an acceleration of the global precipitation kinetics compared to those of the unreinforced counterparts. The microstructures of the consolidated material and heat-treated material were characterized by a high density of plate-like η/η′, and some coarse “fiber-like” precipitates. The “fiber-like” precipitates were identified to be incoherent η 2 or η 4 precipitates. To elucidate the mechanical behavior of the composite, the contributions from various strengthening mechanisms were estimated using existing relationships. In addition, the effects of the reinforcement particles and precipitates on the fracture mechanisms are discussed.