AA Chips come in many forms and options. Generally the metal content for sobriety coins falls into two types. Aluminum AA Medallions are light weight and come in various colors. They are the most inexpensive AA Chips on the market. Often they are sold in packs of 6 or 12 containing Month 1 2 3 6 9 or Months 1 2 3 4 5 6 7 8 9 10 and 11. 24 Hours Aluminum Medallions are also quite common as a gift for new members to AA. The Aluminum AA Chips are always used to recognize the early months of sobriety. I'm not aware of any 1 year or more aluminum AA medallions. Here is a picture of the aluminum chips you may find.
The other type of AA Medallions you'll commonly find are Bronze but actually they are made of Brass. Always referred to as bronze that is probably more a pointer to their color and antique finish. Bronze AA Coins come in Months 1 2 3 4 5 6 7 8 9 10 11 and 18 and 24 Hours and then are made in Years 1 - 65.
Lastly The Fancy AA Chips come in Gold Plating, Silver Plating, Some have a glassy epoxy dome and some even have crystals. Those are usually plated over Brass so generally you could say AA Chips are made of Aluminum or Brass and then you could talk about the coloring or plating that makes the coin fancy.