just saw this thread- couple of thoughts:
first off, if you're really serious about welding rings together and having green chainmail- go copper! Copper turns green as it rusts, so the trick is in getting a consistent shade (if you care about such).
Second, aluminum (depending on your level of "hardcore-ness") CAN work- IF you use the heavier gauges. I'm talking 12 or 14 here- nothing less! I've known quite a few larpers over the years to use it without difficulty. Size of your ID (inner Diameter) is also an important factor, as the larger the ID- the weaker the link. I generally recommend 3/8" ID, though 1/2" might work if you're lighter in build and hardcore requirements.
Third, you could go with a heavy copper shirt made from insulated copper wire (the kind used in wiring by electricians). A bit costly, but the insulation not only adds to the durability- it gives both consistent color AND cuts down on the noise factor (easiest way to make "rogue's chainmail")
Finally, if you don't mind a more "ring mail" look, go with keychain rings and spray paint the mothers! Cheapest option, but you'll have to redo the paint job on a semi-regular basis. Depends if you mind the upkeep....
Just a few thoughts to add to things. Feel free to ask for more. Best of luck on your search!!