Materials research for the future of aviation

How can particularly light yet extremely resilient aluminium components for aerospace be manufactured using industrial 3D printing? This question is the focus of the new ErUM Transfer research project, AlaAF, which the German government funds. The Technical University of Munich (TUM), with its research reactor FRM II, the company Colibrium Additive, and the Friedrich-Alexander University Erlangen-Nuremberg (FAU) want to jointly develop solutions.

FRM II scientists carry out sample measurements with neutrons at the research reactor in Rez near Prague. From left to right: Dr Seda Ulusoy, Dr Massimo Fritton, Simon Sebold, Dr Steffen Neumeier (FAU), Dr Ralph Gilles, Dr Stefan Engel; foreground: Dr Gergely Farkas. © Dr. Vasyl Ryukhtin, NPI Rez

FRM II scientists carry out sample measurements with neutrons at the research reactor in Rez near Prague. From left to right: Dr Seda Ulusoy, Dr Massimo Fritton, Simon Sebold, Dr Steffen Neumeier (FAU), Dr Ralph Gilles, Dr Stefan Engel; foreground: Dr Gergely Farkas. © Dr. Vasyl Ryukhtin, NPI Rez

The focus is on the laser powder bed fusion (LPBF) process, an additive manufacturing process in which metal powder is fused layer by layer using a laser to form high-precision components. This process allows for incredible design freedom. However, it could not be used, for example, with high-strength aluminium alloys, such as those required for load-bearing structural elements in aircraft and spacecraft, as they tend to crack when cooled.

Ceramic particles as ‘micro builders’

The project pursues a new approach in which special additives in the metal powder react chemically during the printing process and form finely distributed ceramic particles in the submicrometre range. These particles influence crystal growth in the material by promoting a fine-grained, uniform microstructure, thereby reducing the formation of cracks. This enables the industrial use of aluminium alloys previously considered virtually impossible to print, offering clear advantages such as lower weight, higher load-bearing capacity and more sustainable production through material savings.

During their visit to Colibrium Additive, all project members were given a tour of the factory and had the opportunity to view the large-format 3D printers. In the future, these printers will be used to manufacture more durable aluminium components. © Colibrium Additive, a GE Aerospace company

During their visit to Colibrium Additive, all project members were given a tour of the factory and had the opportunity to view the large-format 3D printers. In the future, these printers will be used to manufacture more durable aluminium components. © Colibrium Additive, a GE Aerospace company

Partners with clear competencies

The three partners are working closely together on the project, which is funded by the Federal Ministry of Education, Technology and Space (BMFTR) with a total of €1.17 million:

The 3D printing company Colibrium Additive is contributing state-of-the-art industrial technology and is working with TUM and FAU to develop the appropriate process parameters for the LPBF process. FAU analyses printed materials and their mechanical properties, in particular using microscopic methods. Researchers at FRM II are responsible for the comprehensive investigation and quality testing of the materials using neutron methods.

Several specialised methods are used at FRM II: Neutron diffraction allows phase distributions and internal stresses to be determined precisely, key parameters for assessing strength and stability. Neutron imaging (radiography and tomography) makes it possible to visualise even the finest cracks or pores deep inside the samples in a non-destructive manner. In general, the greater sensitivity of neutrons compared to X-rays is used to better understand the material’s microstructure.

Dr. habil. Ralph Gilles, project manager at TUM and spokesperson for the consortium, explains the particular advantage of these methods: “Neutrons have a high penetration depth and are therefore ideal for analysing large, additively manufactured components for industry – a task that would be impossible with other techniques.”

The project brings together the expertise of TUM, FAU and Colibrium Additive to develop crack-free aluminium alloys for the aerospace industry. © E. Malter; TUM (R. Müller, R. Gilles); Colibrium Additive, a GE Aerospace company

The project brings together the expertise of TUM, FAU and Colibrium Additive to develop crack-free aluminium alloys for the aerospace industry. © E. Malter; TUM (R. Müller, R. Gilles); Colibrium Additive, a GE Aerospace company

In addition, the combination of neutron experiments with mechanical loading and temperature variation on a testing machine specially developed at the FRM II (BMFTR-funded project HiMat and H2Mat) allows for a realistic simulation of industrial operating conditions. This makes it possible to record the material behaviour under typical operating conditions.