A method of manufacturing hollow articles by superplastic forming and diffusion bonding

A plurality of hollow blades (86) are produced by assembling a plurality of titanium sheets (12,14) and a plurality of titanium blocks (60,62) into a stack (10). At least one of the sheets (12,14) is provided with stop off material on one of its surfaces (18) at a plurality of longitudinally spaced preselected areas (46) to prevent diffusion bonding at these areas to define the hollow interiors of the blades (86). The edges (32,34,42,44) and ends (28,30,38,40) of the sheets (12,14) are welded together and the blocks (60,62) are welded to the sheets (12,14). The assembly is heated and externally pressurised to diffusion bond the sheets (12,14) and blocks (60,62) together. The integral structure so formed is then heated and internally pressurised to superplastically form at least one of the sheets (12,14) at each of the preselected areas (46) to produce a plurality of hollow blades (86). Thereafter the hollow blades (86) are separated from each other by machining and simultaneously producing the aerofoil shapes.