Elevated Temperature Fabrication of Titanium Aerospace Components
In the past, engine aft fairing heat shields have typically been titanium castings. With a current single aisle airplane, these components were converted to sheet metal titanium 6Al-4V details fabricated by hot forming or Superplastic Forming (SPF). This conversion saved approximately 20% in both cost and weight per airplane. When heat shields for a twin aisle airplane were being developed, the engineers were interested in a sheet metal version of their heat shields hoping to achieve similar savings. However, the twin aisle configuration was different from the single aisle and did not allow the details to be simple pieces of formed sheet metal. Instead, these twin aisle heat shields are assemblies of details containing SPF components as well as Superplastically Formed and Diffusion Bonded (SPF/DB) panels. Some of the heat shield components are fabricated using the world's first applications of fine grain 6Al-4V titanium, which was developed to SPF at 775°C, covered by a U.S. patent , instead of 900°C, which is used for standard grain material. The SPF/DB technology being used contains innovative process developments that are covered by several patent applications [2-4]. The twin aisle heat shield assemblies were estimated to save approximately 15% in both cost and weight per airplane. Actual weight measurements of the first assembly showed an additional 5% savings over the calculated weight per engine resulting in a total weight savings of approximately 20% per airplane compared to titanium castings.
Daniel G. Sanders
L. D. Hefti "Elevated Temperature Fabrication of Titanium Aerospace Components", Key Engineering Materials, Vol. 433, pp. 49-55, 2010