alloyage

from The Century Dictionary.

• noun The practice or process of alloying metals; specifically, in minting, the practice of adding to the precious metals a small proportion of a baser one, to harden them, with the object of producing a clear impression when the coins are struck, and of preventing or lessening abrasion while they are in circulation. See alloy, n., 2.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act or art of alloying metals; also, the combination or alloy.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The act or art of alloying metals.
• noun The combination or alloy thus produced.