Abstract
In the present study, AZ91Mg/$\textrm{Al}_2\textrm{O}_3$ short fiber+SiC particulates hybrid metal matrix composites(MMCs) were fabricated by squeeze casting method. Different particulate sizes of 45, 29 and $9\mu\textrm{m}$ were hybridized with 5% volume fraction to investigate the effect of SiC particulates size on microstructure, mechanical and thermal properties such as hardness, flexural strength, wear resistance and thermal expansion. Results show that the microstructure of the hybrid composites were quite satisfactory, namely revealing relatively uniform distribution of reinforcements. Some aggregation of SiC particulates caused by particle pushing was observed especially in the hybrid composites containing in fine particulates($9\mu\textrm{m}$). The hardness and flexural strength were improved by decreasing particulates size, whereas wear resistance improved by increasing particulates size because of large particulates restricting matrix wear from contacted stress. Regardless of particulates size, thermal expansion of composites was the same. This may be because the content of particulates was in all cases 5 volume fraction.1
