Synthesis and Characterization of Al-SiC Nanocomposites Produced by Mechanical Milling and Sintering

Aluminum powder and various volume fractions of SiC particles with an average diameter of 50 nm were milled by a high-energy planetary ball mill to produce nanocrystalline Al-SiC nanocomposite powders. Double pressing/sintering process was used to consolidate powders to cylindrical specimens. It was shown that a double cycle of cold pressing and sintering can be utilized to obtain high density Al-SiC nanocomposite parts without using a hot-working step. High resolution scanning electron microscopy (HRSEM), X-ray diffraction (XRD) and laser particle size analyzer (PSA) were used to study the morphological and microstructural evolution of nanocomposite powders and bulk samples. The role of volume fraction of SiC nanoparticles in grain size of both as-milled and as-consolidated aluminum matrix was investigated. It was found that the presence of the higher SiC particles eventuate to slowly decrease in grain size of aluminum matrix powders. However, this trend is strongly noticeable in grain size of consolidated samples. The pinning effects on grain stability by SiC nanoparticles were quantitatively analyzed. It was found that Gladman's model is in close agreement with the experimentally determined grain size of Al-SiC nanocomposites.