A rotor and a method of making same are provided. The rotor can include a substantially annular segment having a thickness defined between a first side surface and a second side surface, as well as an inner end edge surface and an outer end edge surface. At least one expansion groove can be formed in the substantially annular segment, and can include a substantially straight portion and a substantially curved portion. The substantially curved portion of the at least one expansion groove can form an arc of at least about 90 degrees. The rotor can also include at least one flange extending from an inner end edge surface of the substantially annular segment at an angle not parallel to a radial of the substantially annular segment.