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AssigneeRockwell International Corporation
InventorsEdward D. Weisert, Suphal P. Agrawal
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A method for fabricating superplastically formed/diffusion bonded structures wherein metal blanks of a titanium alloy are joined at selected areas by diffusion bonding and expanded superplastically to form a desired sandwich or integrally stiffened structure. In such method, the metal blanks are treated in selected areas with a "stopoff" material to prevent bonding at those areas during diffusion bonding and to permit forming or shaping at the same areas during superplastic forming. An improved stopoff compound is provided for this purpose, in the form of yttria of relatively coarse particle size, coarser than 5 microns, in a suitable volatilizable vehicle. Such stopoff compound is inert to reactive metals such as titanium at the high diffusion bonding temperatures, and permits relatively low breakthrough pressure-time product during superplastic forming, thereby preventing excessive strain or rupture of the metal through non-superplastic deformation.
A stopoff composition for fabricating a metallic structure from a plurality of metal blanks by superplastic forming and diffusion bonding, to prevent bonding in preselected areas, which comprises as essential component yttria having a particle size greater than 5 microns, and an inert organic liquid vehicle for said yttria, said organic vehicle comprising a binder capable of volatilizing and leaving substantially no organic residue at elevated temperature below the diffusion bonding temperature of said metal blanks.
Dependencies are inferred from the claim text.