Cast material rotor (200,300,500,800) with profiled helical outer surface (208,308,508,808). Cast material layer (502,802) can be disposed between core (504,804) and tube (506,806). Profiled helical outer surface (208,308) can be in tube 206 or cast material layer 302, respectively. Method of forming rotor 200 can include filling void between outer surface 212 of core 204 and longitudinal bore 210 of tube 206 having profiled helical outer surface 208 with cast material 202 in fluid state, and solidifying cast material 202. Tube 206 can be disposed within profiled helical bore 714 of mold 700, e.g., before solidifying cast material 202. Method of forming rotor 300 can include filling void between outer surface 312 of core 304 and profiled helical bore 714 in mold 700 with cast material 302 in fluid state, solidifying cast material 302 to impart profiled helical outer surface 308 thereto, and removing mold 700 from cast material 302.