Developments in Design and Materials for Cast SPF Tooling

Large titanium and aluminum sheet parts can now be formed into very complex assemblies by the process of superplastic forming. This has resulted in the need for major work to develop new alloys, new design methods and new manufacturing routes to ensure the production of high quality tooling. SPF tooling represents a significant part of the total cost of producing the super-plastically formed part. Careful selection of the material and its manufacturing route is essential in order to obtain the “right quality at the least cost” commensurate with the conditions of use. For many years the optimization of the alloy composition, the melting and casting foundry techniques and the design of the tools was done in a semi-empirical way, being largely based on practical experience. This method meant that the development was slow and unwieldy, and therefore, not compatible with the rapidly changing constraints of the SPF industry today. The fact that extremely powerful modelling programmes such as ThermoCalc and DICTRA are available for the design of new alloys, or Thercast for the optimization of the foundry melting and processing, makes it possible to introduce innovative techniques faster and with more immediate certitude as to their success. Thus, the casting process has become the most competitive and appropriate method of manufacture of the high performance tools in use today. This paper will discuss how these current technologies have been developed, and coupled with the experiences in the foundry, have assisted in the production of new materials, that optimize the tooling required in SPF operations. This article was presented at the AeroMat Conference, International Symposium on Superplasticity and Superplastic Forming (SPF) held in Seattle, WA, June 6-9, 2005.