Though why the rest of the materials aren't listed could be because they're primarily a copper/zinc alloy, in other word's brass, of a relatively low copper content—63/37 Cu/Zn but some 70/30 Cu/Zn.

The technique was used to alloy 6063 aluminum scrap with Cu, Zn, and Mg, producing a nanocluster-strengthened aluminum alloy with properties comparable to 7075 aluminum alloy. Image Credit ...