A method of forming a rotor for a turbine engine such that the rotor is formed of two materials including: an inner disk formed from a first material, such as steel, and an outer ring formed from a second material, such as a nickel alloy, having a larger thermal expansion coefficient than the first material forming the inner disk. The ring may include an inner aperture having a conical shape, and the disk may have an outer surface with a conical shape and a diameter with a portion that is larger than a portion of the ring. The ring may be heated such that the aperture expands to a size greater than the largest diameter of the inner disk. The ring may be positioned over the disk and allowed to cool to allow the ring to be attached to the disk. The ring and disk may then be co-forged.