Fabrication of Titanium Aerospace Hardware using Elevated Temperature Forming Processes 2010-01-1834
Titanium is a difficult material to fabricate into complex configurations. There is several elevated temperature forming processes available to produce titanium components for aerospace applications. The processes to be discussed are Superplastic Forming (SPF), hot forming and creep forming. SPF uses a tool that contains the required configuration and seals around the periphery so inert gas pressure can be used to form the material. Of the processes to be discussed, this is the one that can produce the most complex shapes containing the tightest radii. A variation of the process combines an SPF operation with diffusion bonding (SPF/DB) of two or more pieces of titanium together to produce integrally stiffened structure containing very few fasteners. Another process for shaping titanium is hot forming. In this process, matched metal tools, offset by the thickness of the starting material, are used to form the part contour at elevated temperature. The required part geometry usually contains no sharp features that have to be formed. Starting blanks are often preformed in order to get the material as close as possible to the required shape to minimize thickness variation in the final part. The final forming process to be discussed will be creep forming. In this process, there is only a lower tooling surface. The starting material is placed on the tool and weights are then placed on the part, in the areas where forming needs to occur, and this set-up is placed in a piece of equipment for heating, which is typically a vacuum furnace. At elevated temperatures, the weights force the material down to the tool. Since the only forming force comes from the applied weights, only simple shapes can be achieved.