why should I make alloys other than pig iron and steel?
what can they be used for?
my current fort only has zinc can it be used for anything?
Zinc+copper in equal ratio gives you the non-weapon metal
brass, which is worth 3½ times as much as copper or zinc, and unlike zinc, brass is fire-safe. It's also a much cheaper material for yellow objects than gold is.
Tin+copper in equal ratio gives you the weapon metal
bronze, which is worth 2½ times as much as copper or tin (and is a better weapon metal than copper).
Tin+copper in 3:1 ratio gives you the non-weapon metal
fine pewter, which (like bronze) is worth 2½ times as much as copper or tin. 2:1 tin/copper gives
trifle pewter (worth twice as much as copper or tin), and 2:1:1 tin/copper/lead gives
lay pewter (worth 1½ times as much as copper, tin, or lead).
Copper+tin+bismuth in 2:1:1 ratio gives the weapon metal
bismuth bronze, which is worth 3 times as much as copper, tin, or bismuth (and, like bronze, is a better weapon metal than copper).
Nickel+copper+zinc in 2:1:1 ratio gives the non-weapon metal
nickel silver, which is worth 1½ times as much as copper, nickel, or zinc. However, this is a waste of both nickel and zinc; nickel is more useful in pure form (it's magma safe, unlike nickel silver) and zinc is more useful as an ingredient in the much more valuable brass.