Effect of reinforcement on microstructure and mechanical properties of aluminium hybrid composites

Abstract

Al based metal matrix composites are widely used in aerospace and automobile and engineering applications where high strength to weight ratio and good corrosion resistance are of prime importance. In the present investigation SiC/Al2O3 and SiC + Al2O3 particulate reinforced metal matrix composites with varying weight percent of SiC, Al2O3 and SiC + Al2O3 (2,4,6) were produced by a stir casting process. An optical microscope was used to examine the morphology of dendrites and distribution of reinforcement at varying magnification. The porosity content was measured by comparing the theoretical and experimental determined by Archimedean method. Bulk (Brinell hardness test) and Micro(Vickers Hardness test)hardness tests were done. Brinell hardness test has advantage of covering larger area and hence it incorporates all microstructural heterogeneity whereas microhardness gives information abour interface bonding strength between reinforcement and matrix. The results indicated that in case of SiC reinforcement, there is increase in porosity with increase in wt. % of SiC particles and in case with Al2O3 exceptionally high porosity (%) with 4 wt% Al2O3 due to error during casting. However, in case of hybrid (SiC + Al2O3) composite there is increase in microhardness, Brinell hardness, compared to unreinforced A356 alloy and mono composites.