Development of Al–Mg–Sc Thin Foils for Fiber – Reinforced Metal Laminates

Significance 

Fiber metal laminates (FML) are hybrid composite materials built up from interlacing layers of thin metal foils and fiber reinforced adhesives. The need to reduce weight, increase damage tolerance and corrosion resistance was the motivation that led to the development of these new class of materials. Basically, FML possess better mechanical characteristics when compared to both aluminum alloys and composites individually. Most metal foils in use are Al-Cu based and are prone to corrosion due to the high percentage of Cu; a drawback often overcome by subjecting the foils to sophisticated and partially hazardous surface pre-treatment prior to bonding in laminates. On the other hand, it is well known that Al-Mg foils possess excellent corrosion resistance and high ductility properties; however, strength properties are inferior. Contemporary research has revealed that incorporating small quantities of transition metals such as Scandium (Sc) and Zirconium (Zr) could improve the mechanical properties of Al-Mg. Equipped such knowledge, researchers have been able to fabricate alloys such as the 1570C alloy. Regardless, further research is still mandatory, particularly for consideration of the cost of Sc whose market is yet to stabilize.

Furthermore, despite the long-term research of the Al–Mg–Sc alloys, manufacturing of thin sheets (or foils) with a thickness of less than 1 mm is still an issue. The typical defects are buckling and a thickness tolerance. To address this, a team of researcher from the Austrian Institute of Technology: Dr. Evgeniya Kabliman, Dr. Salar Bozorgi and Dr. Johannes Kronsteiner, in collaboration with Engineer Alexey Nikolas at the SMW Engineering Ltd (now at 2AM, SIA) in Russia has studied a process for the production of Al–Mg–Sc thin sheets with different controlled thickness. Their work is currently published in the research journal, Advanced Engineering Materials.

For this purpose, the research team designed a special alloy based on the 1570C alloy. The special alloy has reduced Mg content and a different rare earth element. Consequently, a special rolling technology for production of thin metal foils with a maximal thickness of 0.5 mm at a semi-industrial scale was also developed. The microstructure of the samples was subsequently characterized by using the metallography, EBSD, as well as SEM/EDX techniques. Additionally, in order to eliminate the rolling defects, the researchers subjected the thin sheets to hot pressing. Lastly, numerical simulations of asymmetric hot rolling by using Finite Element Method were performed.

The authors reported that the mechanical properties of produced Al–Mg–Sc foils with a thickness of 0.5 mm achieved 377 and 419 MPa for yield and ultimate strength, respectively, with the elongation at break about 11% (in the longitudinal direction). Remarkably, the estimated average corrosion rate of the Al–Mg–Sc sheet material with a thickness of 2.7 mm was observed to be not more than 0.006 mm/year.

In summary, the study by Dr. Evgeniya Kabliman and her colleagues presented an in-depth investigation on the manufacturing process of the Al–Mg–Sc thin foils with the thickness of 0.5 mm, in a lab and semi-industrial scale. Generally, by applying the semi-continuous casting, the alloy was produced and thereafter rolled into thin foils with a thickness of max. 0.5 mm by using the duo rolling mill. Overall, the rate of fatigue crack growth was found to be lower than for a conventional AA2024-T3 sheet material as well as the material density (2.65g cm-3).

The manufacturing process was studied mainly in the lab scale, however, the produced Al–Mg–Sc alloy (AFML1) might be considered as a perspective material for aeronautical applications, in particular for fiber metal laminates. The produced laminates showed similar mechanical properties when compared to GLARE 3-3/2 by the reduced weight and better corrosion resistance of metallic layers made of the AFML1 alloy.

The work was conducted within the project “AeroFML – Development of innovative Al-Mg-Sc Fibre Metal Laminates for aeronautical applications” ID # 128 funded by the DLR Project Management, the Austrian Research Promotion Agency (FFG) and the Foundation for Assistance to Small Innovative Enterprises (FASIE).

About the author

Dr. tech. Evgeniya Kabliman is currently as a Senior Scientist at Light Metals Technologies Ranshofen, a subsidiary of the Austrian Institute of Technology. She has joined the team in 2012 and is focusing on metal forming processes. She has her expertise in the field of materials modelling and experimental validation along the production chain with a focus on microstructure evolution.

Dr. Kabliman has received her bachelor and master’s degree in Applied Physics and Mathematics at the South Urals State University in Chelyabinsk, Russia in 2006 and 2008. Then Dr. Kabliman postgraduate in Technical Sciences from TU Wien in Vienna, Austria in 2011. She has published more than 20 research articles in journals and conference proceedings.

About the author

DI Johannes Kronsteiner is currently as a Scientist at Light Metals Technologies Ranshofen, a subsidiary of the Austrian Institute of Technology. He has joined the team in 2013 and is working in the field of structural mechanics and process simulation. He specializes in numerical process simulations using finite elements and novel alternative techniques as well as a material model development for bulk forming processes.

DI Kronsteiner has graduated from a technical school for automation engineering (HTL) in Waidhofen/Ybbs, Austria and then worked for over 5 years as a design engineer in the automotive industry. In 2013 he received a master’s degree in Mechanical Engineering at the University of Applied Sciences Upper Austria and is currently finishing the Ph.D. studies at Johannes Kepler University in Linz, Austria.

About the author

Dr. mont. Salar Bozorgi is currently working as a Scientist at Light Metals Technologies Ranshofen, a subsidiary of the Austrian Institute of Technology. He has joined the team in 2012 and is working in the field of casting and material development. He emphasizes his research on the optimization of aluminum and magnesium casting alloys.

Dr. Bozorgi has received his master’s degree in metallurgy at the University of Leoben (german, Montanuniversität Leoben), Austria in 2008. In 2011 he has post-graduated in Metallurgy and Corrosion Science from the University of Leoben. Then Dr. Bozorgi worked for Nemak Linz GmbH. Since 2015 he is a lecturer at the University of Applied Sciences Upper Austria.

About the author

Ing. Alexey Nikolas has been working for SMW Engineering Ltd. in Saint Petersburg, Russia for several years. Since 2012 he is focusing on the development of high-strength Al-Mg-Sc alloys as well as on processing technology. In 2015 he has initiated and coordinated the project “AeroFML – Development of innovative Al-Mg-Sc Fibre Metal Laminates for aeronautical applications”. Ing. Nikolas is currently a CTO of a start-up 2AM, Ltd in Latvia, which specializes in R&D and production of Al-Mg-Sc wires for additive manufacturing. He is also an author of several patents.

Reference

Evgeniya Kabliman, Salar Bozorgi, Johannes Kronsteiner, Alexey Nikolas. Development of Al–Mg–Sc Thin Foils for Fiber-Reinforced Metal Laminates. Advanced Engineering Materials 2019, volume 21, 1800462.

Go To Advanced Engineering Materials

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