Titania: Technological leap forward in titanium sheet forming

Challenges facing the aviation industry and the importance of titanium

The aviation industry is facing major challenges as part of the Green Deal. In addition to reducing CO₂ emissions, the industry must develop more environmentally friendly production technologies. Titanium is indispensable in the aviation industry, as its unique properties (e.g. high specific strength, corrosion resistance, low density) mean that it cannot be replaced by other materials that can be produced in a more energy-efficient manner.

However, the processing of titanium, especially the widely used α-β titanium alloy Ti-6Al-4V, is extremely demanding. Conventional forming processes are energy-intensive and complex. Superplastic forming (SPF) in particular requires high temperatures (e.g. 840-930 °C for Ti-6Al-4V) and low forming speeds. In addition, a brittle, oxygen-rich phase ("α-case") forms on the surface during prolonged exposure to air and high temperatures, which must be removed by complex chemical etching or blasting.

LKR innovation: efficient deep-drawing process below 500°C

A key focus of the LKR Light Metals Competence Centre Ranshofen is on reducing process costs, time and energy consumption in order to support CO₂ reduction targets in light metal technology. These goals are being pursued in the COMET project ProMetHeus / sub-project Titania, which aims to achieve improvements in titanium sheet forming.

LKR has developed an innovative hot deep-drawing process that shows that α-β titanium sheets can be excellently deep-drawn at temperatures below 500 °C. This method enables the use of hot-work tool steels as forming tools - instead of expensive nickel-based alloys required for temperatures above 600 or 700 °C. This further reduces overall costs and paves the way for industrial application.

As isothermal forming at 500 °C or below is not successful, the process involves preheating the sheet to a temperature below the SPF temperature before transferring it to the press.

Initial successes and patenting

Initial trials with a specially developed hot-work tool led to the successful forming of a test component with a depth of 44 mm in 2022. Based on these promising results, LKR applied for an Austrian patent around a year before the start of ProMetHeus-Titania and filed a PCT patent within the priority period. Further optimisations in the project confirmed the robustness of the method, resulting in a drawing depth of 68.5 mm - the maximum depth of the test tool.

This outstanding result shows that the formability of Ti-6Al-4V with our process has great potential for a wide range of applications.

Further development and industrial benefits

As part of the project, the preheating time, preheating temperature and deep-drawing temperature were further reduced. Several tests with Ti-6Al-4V sheets with different surface finishes, provided by our industrial partner voestalpine BÖHLER Bleche GmbH & Co KG, showed excellent reproducibility. It is particularly important that our process also works successfully with rougher sheet surfaces. This reduces the amount of grinding required and therefore offers a considerable advantage for industrial applications.

The mechanical properties are also promising: an elongation at break of over 10 % was achieved without additional heat treatment after the deep-drawing process. This suggests that multi-stage forming processes in more complex tools will be possible in future without intermediate heat treatment. Initial trials with a two-stage forming process have already been successful.

Another decisive advantage of our process compared to conventional Ti-6Al-4V forming methods is the absence of the brittle α-case layer on the component surface. This is due to the comparatively short high-temperature exposure, which thermodynamically limits diffusion processes and oxygen absorption into the α-titanium.

Georg Kunschert, the project manager of ProMetHeus-Titania, summarises: "Our novel technology offers numerous improvements over existing Ti-6Al-4V forming processes and represents a real success story within the COMET project ProMetHeus. The results to date form a promising basis for the industrial commercialisation of this innovative titanium forming process - with great potential for industries such as aerospace, chemical apparatus engineering and medical technology."