Method of manufacturing an article by diffusion bonding and superplastic forming

A method of manufacturing an article of predetermined finished profile by diffusion bonding and superplastic forming at least two metal workpieces comprising the steps of:

• (a) forming a metal slab, the metal slab having first and second ends and first and second surfaces,
• (b) forging the first end of the metal slab to produce a region of increased thickness at the first end of the metal slab and extending from the first surface of the metal slab and forging the second end of the metal slab to produce a region of increased thickness at the second end of the metal slab and extending from the second surface of the metal slab,
• (c) machining the metal slab from the first surface to the second surface to form two metal workpieces, each metal workpiece has at least one surface,
• (d) applying a stop off material to prevent diffusion bonding to preselected areas of at least one of the surfaces of at least one of two metal workpieces,
• (e) assembling the at least two metal workpieces into a stack relative to each other so that the surfaces are in mating abutment,
• (f) applying heat and pressure across the thickness of the at least two metal workpieces to diffusion bond the at least two metal workpieces together in areas other than the preselected areas to form an integral structure,
• (g) heating the integral structure and internally pressurising the integral structure to cause the preselected area of at least one of the at least two metal workpieces to be hot formed to produce a hollow article of predetermined shape.