Development of new methods to recycle light alloys from welded aircraft structures

The ReINTEGRA Clean Sky project is led by AZTERLAN Metallurgy Research Centre and participated by the company SONACA (Belgium) and CIDETEC technology centre as well as by two industrial advisors (the company AIR, from Spain, and the company CONSTELLIUM, from France).

Recovering metals at the end of life of aircrafts is a key strategy to improve resource efficiency and the economic and environmental sustainability of the air & space sector. With this aim the ReINTEGRA European Project, funded within the Clean Sky 2 program, focuses its research efforts in the development of advanced dismantling and recycling processes of aircraft panels assembled by means of LBW Laser Beam Welding and FSW Friction Stir Welding technologies.

As described by the AZTERLAN researcher Mrs. Clara Delgado (an expert in sustainability and environmental issues), “in order to have a more sustainable end of life of aircrafts, the new methods developed must maximise the recovery of metallic alloys in compliance with the quality standards that allow to use them back in high added value applications, without losing critical and valuable alloying elements and avoiding the formation of impurities that would require dilution with primary aluminium”. The aim for recovered metals is to become the “main mine” of Europe. This will allow to achieve as well, more cost competitive and energy efficient materials and processes.

With that purpose, the ReINTEGRA team led by AZTERLAN Metallurgy Research Centre (member of BRTA) and participated by SONACA aircraft manufacturer (Belgium), along with CIDETEC technology centre (also a member of BRTA) and 2 industrial advisors (AIR aircraft dismantling company and CONSTELLIUM aluminium alloys manufacturer), will investigate different aircraft-part separation and sorting strategies to evaluate their impact on the product obtained from recycled welded structures which mix 3rd generation Aluminium-Lithium (Al-Li) materials, welding methods and innovative protective layers.

As explained by Ph. D. Ana Isabel Fernández, researcher from AZTERLAN Aluminium and Light Alloys Department “Al-Li alloys are up to 4 times more expensive than other aluminium alloys used by the aircraft manufacturing industry, mainly due to their high content of lithium, silver and other precious metals. Even though aluminium can be practically endlessly recycled, recovering other metals part of these alloys is still a challenge”. Regarding the Lithium, it can be lost during the re-melting process if these operations are not performed under a protective atmosphere. On the other side, silver can become an impurity within the recycled metal if not treated correctly.

Therefore, the main challenge behind the project is to demonstrate that aircraft alloys can be re-melted into alloys of the same family without major adjustments, so that sorting and separation of components can be minimized (or even eliminated) during the end of life of aircrafts. In the same line, the research team will also develop uncoating processes to eliminate layers of paint and surface treatments applied on the fuselage for aesthetic and corrosion protection purposes. If they are not properly eliminated, these coatings can incorporate impurities in the re-melting process that might affect the application of the recovered alloys as high added value alloys.

The new disassembly and recycling processes will be tested in welded coupons and in demonstration panels. The metallic parts separated will be processed at the AZTERLAN Pilot Foundry Plant to produce ingots that will undergo several advanced characterisation tests. “We will be able to evaluate the efficiency of the process in terms of cost, environmental impact and effectivity at recovering metals and, therefore, to select the most suitable alternatives for welded panels”.

Experimental data obtained from recyclability tests and characterisation analyses will be the basis to develop a new modelling software to estimate the recyclability of any FSW and LBW assembled structure that combines Al-Li alloys to be used back in aeronautic alloys. Also, energy and materials flows, emissions and waste will be inventoried during the tests to estimate the environmental impact of the proposed recycling processes. All these data will be uploaded to the aeronautics Life Cycle Assessment database being built.

This project is funded under the Clean Sky 2 Joint Undertaking (JU) with the grant agreement Nº 886609. The JU receives support from the EU Horizon 2020 research and innovation programme and the Clean Sky 2 JU members.

Aircraft disassembly process for recycling purposes