As I understand it: A changing magnetic field will create an electric field (see Maxwell's Equations) which will induce a current in any conductor, including aluminum. You will create a giant aluminum disk heater because the currents in such a disk will loop around and short circuit within the disk, that is what an eddy current is. Laminated steel is used in many motors and alternators. Laminated steel is used instead of solid steel to limit these eddy currents and with the steel the magnetic flux across the coil can be increased. It is a trade off. Larger magnetic flux results in greater electric field flux, and greater induced voltage, but you lose a bit of energy to eddy currents as well. In most of the axial wind turbines, greater magnetic flux is obtained by using massive magnets as opposed to having the losses of a laminated steel stator. Rich