A356 is for Steel Castings, Carbon, Low Alloy, and Stainless Steel, Heavy-Walled for Steam Turbines
In A356, grade 6 has a minimum of 80 ksi UTS and 18.0% elongation. Although those numbers match closely, grade 8 is a 1%C, 1%Mo, Va alloy. I dont htink it has anything to do aluminum.