IMO, Americast is the spam of metals. I was looking for a new kitchen
sink last year and spent some time investigating the alternatives. In
all my searching, I never could find exactly what Americast is made of.

Clearly, the advantages are weight and cost (at least in the case of my
sink, Americast would be significantly cheaper). But, do this test.
Go to one of the big stores and take a good look at Americast vs a
Kohler cast iron product next to each other. The sinks are probably
the easiest to see side by side. IMO, there is no comparison. The
Kohler cast iron has a rich, luxurious appearance. Slightly rippled
from the texture of the underlying casting. The Americast looks good
for what it is and costs, but be sure you understand the difference
before you buy it.