Alot of ships have had alluminum superstructures. The first full class of ships was the SPRUANCE class (Best Destroyers ever) The Oliver Hazzard Perry class Frigates and the Ticonderoga class cruisers. The problems are the bi-metallic corrosion on the special alluminum/steel joint that allows them to weld the superstructure to the hull. And the other was show by the USS STARK incident where unused fuel aboard the missile that hit it caused more damage by starting a fire that got so hot the alluminum istelf was burning. All Arliegh Burkes are completely made of steel as a result.