Microstructure and tensile properties of bulk nanostructured Al-5083/SiCp composites prepared by cryomilling

In order to develop high-strength and lightweight MMCs, nanostructured composite powder consisting of an Al-5083 matrix reinforced with approximately 6.5 vol.% nano-sized SiC particles (25 nm in size) was synthesized via cryomilling. Two bulk composites made from 100% of the composite powder and a blend of the composite powder with 50 wt.% conventional coarse-grained (unmilled) Al-5083 powder, respectively, were fabricated with HIP-consolidation and hot rolling processes. Microstructural investigation showed that the nano-sized SiC particles had been dispersed homogeneously in the reinforced regions in the composites and the grain size of the Al-5083 matrix in the reinforced regions ranged from 100 to 200 nm. However, coarse-grained SiCp-free regions were observed even in the composite made from 100% composite powder after HIPping. The tensile strength of the composite made from 100% composite powder was 26% higher than that of nanocrystalline Al-5083 without reinforcement. The existence of coarse-grained regions improves the ductility of the composite.