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The reason you see the materials you mentioned being used the most often , particularly 1084 and 15N20, is because of what I call their compatibility. That being the rates the materials move, when heated or cooled. In other words their expansion and contraction rates. The more difference in the expansion and contraction rates of the alloys used, the more problems it manifests, and if you introduce multiple alloys into a damascus mix with differing expansion and contraction rates, the problems are magnified.
For example, when you mix 1084 and 15N20..... 15N20 is basically 1075 steel, with 1.5% nickel added. In terms of expansion/contraction, these two steels are nearly identical.....minimal to no problems.
Now, lets say you take that same 1084, and mix it with L6...... very different expansion/contraction rates.... it will forge weld just fine, but because of the vastly different rates of expansion/contraction, warping becomes an issue.... from the forging stage on. The step that generally causes the most issues with this type of mix is the heat treat, namely the hardening step. Often times damascus blades made with "incompatible" steel will warp severely in the hardening step. and in some case will even tear themselves apart at the laminations. So let's now say that you introduce another one or two alloys that have varying degrees of compatibility with the 1084 and L6...... you just compounded the probability of issues you face.
The moral of the story being..... it's important to understand the mechanics of materials you choose for damascus, in order to be successful. I get a lot of requests for help from folks with their damascus problems..... I've learned to asked right off the bat, what alloys they are using....and in most cases those who are experiencing problems are trying to put together two or more alloys that simply will not "play well together".
OK, more directly to your question...... when it comes to building damascus, there is always a "give-n-take"....meaning that in order to get something you want in one area, it's often necessary to give up something in another area. Are you looking for eye appeal? Are you looking for performance? How much of one are you willing to sacrifice for the other? See where I'm going? "Eye appeal" is generally going to involve an alloy that contains nickel, whish is always the silver/bright portions of a damascus mix, but nickel is none hardenable beyond a given percentage (usually 10% nickel is the max an alloy can contain and still be considered hardenable) so there's it's "trade off". Those steels that offer increased performance over those with nickel are alloys that will generally appear dark or "black" in the finished product. So there's always at least some "give-n-take" when it comes to choosing steels for damscus. As things stand right now, 1080 or 1084 and 15N20 are the most "compatible" steels available for creating damascus.....which is why it's the most used. So, all that being said, you won't get too much noticeable variance in colors/shades by using various alloys in a single damascus mix, but you will get far more problems to deal with. My advice is to think of "stacking" 1080 and 15N20 in different configurations....rather then say a 1:1 ratio, stack several layers of one, and fewer of another to give a more bold appearance in either the "black" or the "silver" areas of the finished blade(s). You can pretty much get the best of everything through that method, with only very minor "trade offs".
Whew! Sorry for rambling on so much..... but some things just deserve a good explanation,
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