Process Development for a Superplastic Hot Tube Gas Forming Process of Titanium (Ti-3Al-2.5V) Hollow Profiles

Abstract

Tube forming technologies based on internal forming pressures, such as hydroforming or hot tube gas forming, are state of the art to manufacture complex closed profile geometries. However, materials with excellent specific strengths and chemical properties, such as titanium alloys, are often challenging to shape due to their limited formability. In this study, the titanium alloy Ti-3Al-2.5V was processed by superplastic hot tube gas forming to manufacture a helically shaped flex tube. The forming process was investigated in terms of process simulation, forming tool technology and process window for the manufacturing of good parts. Within a simulation study, a strain rate optimized forming pressure–time curve was defined. With the newly developed tool design, forming temperatures up to 900 °C and internal forming pressures up to 7 MPa were tested. A process window to manufacture good parts without necking or wrinkling has been successfully identified. The experiment data showed good agreement with the numerical simulations. The detailed study of the process contributes to an in-depth understanding of the superplastic forming of Ti-3Al-2.5V during hot tube gas forming. Furthermore, the study shows the high potential of superplastic hot tube gas forming of titanium alloys for the manufacturing of helical flex tubes and bellows.

Superplasticity and Superplastic Forming

“…They show how excessive thinning and the consequent fracture can be predicted only if a correct choice of the constitutive equation is made. The contribution by Trân, et al [8] is focused on the hot gas forming process of Ti tubes for producing hollow profiles. By means of numerical simulations, the authors were able to identify a process window with an appropriate pressure profile for the manufacturing of sound parts, avoiding necking or wrinkling.…”

Experimental Investigation of Current Intensity and Feed Speed in Electrically Assisted Necking and Thickening of 5A02 Aluminum Alloy Tubes

“…Due to the poor formability of hard-to-form metals such as aluminum alloy at room temperature, it is difficult to achieve thickening for the straight end of the tube necking zone. In the current research, thermally assisted forming [1][2][3] and electrically assisted forming [4][5][6] have been proven to be effective means in terms of reducing forming flow stress and improving formability for different hard-to-deform alloys.…”

Influence of surface pressure and tool materials on contact heating of aluminum

“…These concepts involve design changes e. g. in order to realize integration of functions [5] and the use of typical lightweight materials such as high strength steel [6] or light-metal alloys [7]. These materials usually feature limited formability at room temperature so that forming of the complex geometries typically necessary for lightweight components frequently requires thermo-mechanical processes such as press hardening [8], quenching and partitioning [9], or superplastic forming [10]. In this context, fast and energy-efficient heating strategies are an essential prerequisite.…”