Welcome, Chuck! I hope you spend many happy hours in your shop! Doing things like this will keep you healthier longer, I have found..
I have quit buying metal from scrap yards, unless it is simple angles and such.
When you buy at a scrapyard, you pretty much get mystery metal. Also you have to buy a 5 ft. piece, that you only need to take 3" out of, and you are stuck with increasing amounts of scrap that you really have no use for.
I use Speedy Metals. They are very good, and you can buy by the inch of length, so no need for extra material that lays around. If you buy in 12" lengths, you can stock your own shelves with the metals you need most for your projects. It is true they are more expensive than a scrapyard, but you are paying for the convenience of only needing to buy 3" of material, so that is the tradeoff. To me it is worth it. Plus, by buying from places like this, you support the amateur machine shop industry, by keeping your suppliers in business.
I also use "Industrial Metal Supply". They have a local warehouse, and they sell material in 1 ft lengths, 3 foot lengths, or cut to size from 20 ft. standard lengths of steel, brass, bronze, and aluminum. Industrial Metal ALSO sells precut rounds, ranging from 1/2" thick by 3" diameter, to 12" diameter and 4" thick. If you need something like this, you DON'T want to be buying a giant piece, and then having to cut it so you can use it. Plus, as I mentioned above, you KNOW what the material is. The other thing is, Industrial Metal Supply has an "artist corner" where they sell small cutoffs of stainless, brass, copper, steel, etc. that are left over from their industrial cutting operations. These are sold by weight, so if you are talking about 3 square inches of 1/8" copper sheet, they will probably just wave you out the door. They do that a lot with me, (They know me well, and that I work on model steam locomotives, so use various materials in small amounts) and I know they have done it with other members of our local machining club.)
When I started machining, I used to go to scrapyards, but I don't do that anymore. It's kind of a waste of time and money, even if a particular piece of material is cheaper. You still had to spend time chasing around to find it, and you still don't know exactly what it is.