A type II superconducting alloy which is superconducting at a predetermined high magnetic field is prepared by creating a composite having a periodic arrangement of at least two transition metals so as to provide numerous interfaces between the different transition metals including niobium, titanium, zirconium, vanadium, hafnium, and tantalum, and alloys thereof. The combination of transition metals is such that one of the metals will serve as a second phase when the layers are subjected to temperatures which would produce a two-phase equilibrium state from a solid solution alloy of the transition metals. The composite is mechanically reduced and heated to cause interdiffusion of the transition metals to form ductile superconducting alloy zones at the interfaces of the transition metals. Sufficient heat treatment is provided in the region where two phases exist in the phase diagram to form two phases, one phase being the desired superconducting Type II alloy and the other phase being the non-superconducting normal metal or alloy. The temperature of heat treatment is limited to the two-phase region. Thereafter, the composite is mechanically reduced so that the two zones are each less than about 1,000 nm in thickness.