Impeller with circumferential thickness variation

A radial flow impeller comprises an impeller body 34 and a plurality of vanes 32 depending there from, wherein the impeller body 34 varies in thickness in a circumferential direction. The impeller body 34 may have a hub portion and a radially outer circumferential rim arranged about a common axis, the vanes 32 extending from the hub portion towards the rim, and the sectional thickness profile of the impeller body 34 varying in a cyclic manner. Alternatively, a method of manufacturing the impeller may comprise determining or predicting a stress distribution within the impeller body 34, determining a desired sectional thickness profile for the impeller body 34 based upon the stress distribution, and producing the impeller according to the sectional thickness profile. The number of cycles of variation in the thickness of the impeller body 34 may be dependent upon, and preferably equal to, the number and spacing of the vanes 32. The impeller body 34 may comprise one or more circumferential bands 46 in which the thickness of the impeller body 34 varies. The impeller may be part of a compressor or turbine, preferably located in an engine.