This article examines the reasons for the poor performance of the nanometric scale SiC (n-SiC p ) particulate-reinforced Al 7075 composites. The composites having different volume fractions of the n-SiC p were synthesized via powder metallurgy (P/M) route and were uniaxially tested at room temperature. Experimental results showed a significant drop in the hardness and tensile properties of the composites in comparison with those of the monolithic Al. Microstructural analysis via scanning electron microscopy (SEM) revealed large segregation of Mg in the vicinity of the n-SiC p and at the grain boundaries of the Al matrix, which plausibly changed both the aging kinetics and tensile behavior of the Al matrix. The segregation of Mg increased with an increase in the volume fraction of the n-SiC p in the Al matrix. No Mg segregation was found in the monolithic Al. The clustering of the n-SiC p was observed from SEM with energy dispersive X-ray analysis. SEM also revealed cracks in the n-SiC p clusters and debonding between the clusters and Al matrix, which were considered as the main mode of fracture in the composites.

The tensile behaviour of nanometric SiC particulate (SiCp) reinforced aluminium matrix composites (AMCs) was examined at room temperature, 215°C and 350°C. These AMCs were produced via powder metallurgy (P/M) using Al 7075 powder reinforced with different volume fractions (1 vol.%, 3 vol.% and 5 vol.%) of nano-SiCp. The experimental results exhibit that at room temperature un-reinforced Al has both maximum strength and ductility whereas the 5 vol.% SiCp/Al composite has only maximum stiffness. Similar trends were obtained for tests performed at 215°C. However at 350°C, the 1 vol.% SiCp/Al composite has the highest stiffness. Optical microscopy and scanning electron microscopy were performed for microstructure study, examination of the SiCp distribution in the Al matrix and fractography.

This article studies the influence of nanometric (n-SiC p ) and micrometric-scale SiC particulates (l-SiC p ) on the tensile properties of the Al 7075 alloy. The unreinforced Al and its composites were synthesized using the powder metallurgy (P/M) route and were tested uniaxially in tension at both room and elevated temperatures. Aging behavior was studied to observe any effect of the reinforcement on the aging kinetics and hardness of the composites. X-ray diffraction was performed to determine the crystal structures of the raw materials and any reaction phase formed in the composites. The n-SiC p were not dispersed uniformly in the Al matrix and clustered mainly at the grain boundaries. The stiffness of the composites increased and the ductility decreased with an increase in the volume fraction of the n-SiC p . The n-SiC p proved to be a better reinforcement than the traditional l-SiC p in terms of imparting higher ductility to the composite. Fractography and microscopy using optical, scanning electron, and transmission electron microscopes were performed for failure and microstructural analysis of all the materials. At room temperature, the fracture altered from ductile in the unreinforced Al to brittle in the composites. At an elevated temperature, the fracture mechanism transformed from brittle to ductile rupture in the composites.

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