area in the microstructure of the SiC nanocomposite tablet. Also, the EDX mapping of an area for the tablet containing TiB2 nanoparticles is presented in Figure 8. The Ti map illustrates where the TiB2 nanoparticle clusters were located. In order to further examine the degree of contact between the nanoparticles and aluminum in the compact, TEM studies were conducted for the SiC and TiB2 tablets as shown in Figures 9 and 10, respectively. It is clear from both figures that the compaction of the aluminum powders and nanoparticles has induced relatively effective embedding of nanoparticles in the aluminum at the interface, as indicated in Figures 9b and 10b with arrows. B. Microstructural Characterization of the Fabricated Nanocomposites Figure 11 compares the optical micrographs of: the pure A356 alloy; ultrasonically processed A356 alloy for 30 minutes at 670 °C without the addition of nanoparticles; and the fabricated nanocomposites (A356/0.8 wt.% SiC and A356/0.8 wt.% TiB2). It can be seen from Figure 11b that ultrasonic treatment of the alloy without nanoparticles has noticeably refined the microstructure changing the morphology of grains from large dendrites to a α-aluminum relatively fine and globular structure with eutectic located in interglobular regions compared to the pure alloy (Figure 11a). However, the ultrasonically treated alloy still displays some dendrites as marked with the dashed lines in the microstructure. Figures 11c and 11d show the typical microstructures of the A356/0.8 wt.% SiC and A356/0.8 wt.% TiB2 nanocomposites, respectively. In comparison to the ultrasonically processed A356 alloy, large dendrites were further broken, and grains were refined upon the addition of α-aluminum nanoparticles. Comparing Figures 11c and 11d there is little difference between the effects of SiC and TiB2. The microstructure of a slice cut from a typical nanocomposite (A356/SiC) was investigated in order to document any microstructural changes created in different
area in the microstructure of the SiC nanocomposite tablet. Also, the EDX mapping of an area for the tablet containing TiB2 nanoparticles is presented in Figure 8. The Ti map illustrates where the TiB2 nanoparticle clusters were located. In order to further examine the degree of contact between the nanoparticles and aluminum in the compact, TEM studies were conducted for the SiC and TiB2 tablets as shown in Figures 9 and 10, respectively. It is clear from both figures that the compaction of the aluminum powders and nanoparticles has induced relatively effective embedding of nanoparticles in the aluminum at the interface, as indicated in Figures 9b and 10b with arrows. B. Microstructural Characterization of the Fabricated Nanocomposites Figure 11 compares the optical micrographs of: the pure A356 alloy; ultrasonically processed A356 alloy for 30 minutes at 670 °C without the addition of nanoparticles; and the fabricated nanocomposites (A356/0.8 wt.% SiC and A356/0.8 wt.% TiB2). It can be seen from Figure 11b that ultrasonic treatment of the alloy without nanoparticles has noticeably refined the microstructure changing the morphology of α-aluminum grains from large dendrites to a relatively fine and globular structure with eutectic located in interglobular regions compared to the pure alloy (Figure 11a). However, the ultrasonically treated alloy still displays some dendrites as marked with the dashed lines in the microstructure. Figures 11c and 11d show the typical microstructures of the A356/0.8 wt.% SiC and A356/0.8 wt.% TiB2 nanocomposites, respectively. In comparison to the ultrasonically processed A356 alloy, large dendrites were further broken, and α-aluminum grains were refined upon the addition of nanoparticles. Comparing Figures 11c and 11d there is little difference between the effects of SiC and TiB2. The microstructure of a slice cut from a typical nanocomposite (A356/SiC) was investigated in order to document any microstructural changes created in different