Suppose you have a supply of the following metals: Fe, Ni,Sc, Cr, Au, K. Which of there could be mixed to make substitutional alloys? Which metals are incompatible for this purpose. Clearly explain why there metals would be incompatible.

I am unsure about the metals that are incompatible. I think the metals that answer this part are K and Sc because they are so far away on the periodic table from the other elements that all have similar sizes. Help?!