I have seen welding rods for aluminium, they require preheating of the materials and a god welder.
For soldering, I have tried soldering wires onto aluminium foil for a glass coating tester during my apprenticeship. I recall it as difficult, but possible with sandpaper and lots of flux. (The rough surface helps.)
lots of "kits" for this, on ebay, but almost all of them says "low temp" and then say "use propane torch" ..... yeah, it doesn't look really "low", as temp
Time by time, also some "kit" pops out, but, like this one, the seller never write any technical specification, about it (the image is not too clear, but i think it say 1070F melting point) ..... or this alloy (it say 728F melting point) ..... but, i've found no similar products, distributed in Italy, for try to compare them ..... anyone in the USA know what this product is, and what are the technical specifications, or have already tried them ?
Anyway, i doubt that there is something that can be used with a normal soldering iron ..... :thinking: ..... maybe some "special" indium alloy ..... but the costs looks insane ..... probably the better way for solder aluminium is still TIG under argon flow .....