Superplastic forming and diffusion bonding (SPF/DB) is a technique allowing the manufacture of complex-shaped hollow metallic parts. It combines Superplastic forming (SPF) with a second element "Diffusion Bonding" to create the completed structures.
Two metal sheets are welded together at their edges, then heated within the confines of a female mould tool.
When the part is hot, an inert gas is injected between the two sheets ; the part becomes hollow to the form of the mould.[1] Parts may be welded in other areas than the edges to give an internal structure as the sheets are blown.