yes aluminium can displace copper easily. but as such, since its higher in the reactivity series, its extraction is very difficult as well.
the only way is by electrolysis of its ore bauxite to the molten state, normally with a melting point of 2k degrees celsius. thus a catalyst of cryolite is used instead, but then cryolite is not common, and the melting point is still reduced to only 900 degrees celsius. at such high temperatures, the graphite electrolytes eventually burn out, producing CO2 and requiring constant replacement. its actually a very costly process.
your idea of an iron plate is feasible, but it sounds more like a lab experiment than some commerical process o_O