SiC strengtheners are of two types, whiskers of SiC and fibers of SiC.
The sad news, for you, is that they aren't "strengtheners" that you can stir into the melt like you can add additives to oils or gasoline. So, your proposed application is outside of current state of the art.
There is some limited introduction to metal matrix composites (aluminum would be the metal matrix and SiC would be the composite reinforcement) in the web page below:
It isn't just melting and mixing.
You might also find useful information at the site below on metallurgy in general....
homogeneously blended and vacuum-hot-pressed into commercial scale billets as large as 1,000 lbs. DRA billets are transformed into an almost limitless range of wrought products using conventional extrusion, rolling, and forging metalworking techniques.
business. As the first company to achieve market success with series production of commercial and military aerospace components, DWA has the longest and most progressive presence in the the DRA industry. Our dedication to DRA technology and problem solving has enabled our customers to realize significant benefits for their businesses.
Those few words sort of summarize the type of technology needed to stick the Sic inside the Aluminum in a useful way... and it isn't mixing in the molten state for castings.
Good luck with your metal casting sculpture.
Jim