Method of producing diffusion bonded superplastically formed structures

Abstract

Process for producing metallic structures such as T-cap structures of a metal capable of diffusion bonding and superplastic forming, which comprises inserting at least two metal workpieces, for example, a titanium alloy, preferably in the form of sheets or diaphragms, in contact with each other in a tooling apparatus, and providing a space or cavity, e.g., of triangular shape, in the tooling above and below the workpieces along an area thereof. A sharp ridge is provided in the tooling at one end of the cavity to pinch off the workpieces at that point. The workpieces are diffusion bonded at preselected contacting areas thereof. The unbonded areas of the workpieces are then expanded by superplastic forming into contact with a wall of the tooling cavity, forming a hollow, e.g., triangular, cross-sectional shape. According to one embodiment, the cavity is then pressurized to collapse and compress the shaped cross-section back on itself against a wall of the cavity and the collapsed cross-section is diffusion bonded internally to form a thicker T-cap around the periphery of the diffusion bonded workpieces. According to another embodiment, after superplastic forming, the hollow shape, e.g. triangular shape, can be trimmed, to provide a peripheral flange or T-cap on the diffusion bonded workpieces, omitting the collapsing step of the first embodiment.