Innovative Aluminium filler Wires for Aircraft Structures

Project Information

IAWAS

Grant agreement ID: 821371

DOI

10.3030/821371

Project closed

EC signature date 19 September 2018

Start date 1 October 2018

End date 31 October 2022

Funded under

• SOCIETAL CHALLENGES - Smart, Green And Integrated Transport

Total cost

€ 498 923,75

EU contribution

€ 498 923,75

Coordinated by

SOCIETE NATIONALE DE CONSTRUCTION AEROSPATIALE SONACA SA
Belgium

Periodic Reporting for period 3 - IAWAS (Innovative Aluminium filler Wires for Aircraft Structures)

Reporting period: 2021-10-01 to 2022-10-31

Summary of the context and overall objectives of the project

Innovative Al filler Wires for Aircraft Structure (IAWAS) addresses the lack of commercial Al filler wire available on the market for the WAAM and LBW of the new Al-Li alloy parts. The use of Al-Li alloys in the aerospace industry will lead to weight savings since these alloys are characterized by their low density, excellent corrosion resistance, superior fatigue performance, high fracture toughness, and excellent static properties. The development of WAAM of Al-Li alloys will also improve the buy to fly ratio. Indeed, this technology places raw material only where it is needed for part functionality, limiting the amount of chips and offcuts produced during machining. Concurrently, LBW is considered as one the most promising routes for substituting mechanical joining, contributing to weight and cost savings in the aircraft industry.
IAWAS objectives are:
- Developing new wire compositions able to be used in the LBW and WAAM of the 3rd generations of Al-Cu-Li alloys.
Two materials were developed: U817 for WAAM application and J300 for LBW.
- Implementing the new Al filler wires in the LBW and WAAM processes.
The J300 was successfully used for welding 2198 coupons with LBW. Some problems were encountered during the drawing of the U817 wires, which resulted in a wire of low quality. The implementation of the U817 wire was more complicated, giving deposited walls with a high level of porosities.
- Optimising the WAAM process and implementing post-treatments (surface and heat-treatments) in such a way as to obtain material properties in compliance with the requirements of the targeted product.
The properties of the deposited AA2395 wires were unexpectedly low. The development of a suitable process was developed and applied during the third period (through cold working). The heat treatment was optimized and applied on mock-up demonstrators and representative coupons.
- Characterising the microstructure, mechanical properties and corrosion resistance of the optimised post-treated WAAM material in relation to the requirements of the targeted product.
Tensile tests, exfoliation corrosion susceptibility test and microstructural analysis were performed on representative coupons.
- Manufacture by WAAM of two demonstrators representative of the targeted product with a previous combined structural and geometry analysis as well as a cost analysis.
Three demonstrators were manufactured:
o Two mock-up parts were deposited starting from plates of 6082, with a wire of AA2319 with two purposes: de-risk the manufacturing of the final demonstrator and assess its machinability after heat treatment.
o One final demonstrator built with a support plate of 2198 and wires of AA2395 with the optimized process (WAAM with inter-layer peening).
- Evaluating the internal and external quality of the demonstrators
Liquid penetrant inspection and visual inspections revealed the surface defects while the internal defects were analysed with radiography.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

a) Wire drawing and new wire materials
After preliminary extrusion and drawings of wires of AA2395 and 2196, new wire materials were developed based on new aluminium alloys: U817 for WAAM and J300 for LBW. The U817 was very difficult to draw and its poor quality will lead to a high level of porosities after WAAM deposition. The J300 was successfully considered for the LBW trials.
b) LBW development
Several LBW trials were performed with A5024, AA2198 and AA2060 as base materials and AA4047, AA2395, AA2319, J300 and AA2099 as wires. The parameters were optimized but the radiographies revealed large porosities. Tensile tests and fracture surface analyses showed that the high brittleness of the specimens was due to the presence of large defects.
c) WAAM development
Several investigations were carried out to assess the feasibility of producing an Al-Li deposit using WAAM. It consisted in the development of the WAAM process (with peening) and the optimisation of the post-deposition heat treatments. The main result of the WAAM development is the positive effect of the inter-layer peening on the inner quality of the deposition and its mechanical properties. The results of the WAAM investigations were discussed during several workshops and conferences and it is foreseen to published them in two scientific publications.
d) Demonstrator
Two mock-up parts, representative of the demonstrator, were built on a thick and thin supports (6082 plate with 2319 wire). The part with the thinnest plate showed some distortions after the heat treatment. The mock-up parts were routed to assess their machinability after thermal treatment.
The final demonstrator was deposited with the optimized process. Only a stress relief was carried out to avoid the large distortions and ensure the geometrical conformity. The over-thicknesses of the demonstrator were machined and the final demonstrator was inspected visually, with liquid penetrant and radiography. The manufacturing of this part was successful. However, some defects were observed: cracks in the base plate and porosities.
With these activities, it was shown that it is possible to deposit a large demonstrator with Al-Li. The positive effect of the inter-layer peening is also demonstrated.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The project aimed at developing two new filler wires, one for WAAM and one for LBW, implementing the new Al filler wires in the LBW and WAAM processes.
One of the exploitable outputs of IAWAS are the wires with the new compositions able to be used in the LBW and WAAM. The wire developed for LBW does not contain Lithium but showed good results when considered for LBW of Al-Li sheets. The wire for WAAM showed to be difficult to extrude and drawn.
At the beginning of the project, it was expected to reach TRL 9 and to have a product ready to be commercialized. However, due to the difficulty to extrude and mostly to draw the wires, it is not possible to reach an industrial production of these new wires now. Indeed, due to the large difficulties encountered for the production of these wires, UACE and SelectArc focused on the production of some spools in a non-industrial way (not scalable used processes). Additional drawing steps were needed and, in some cases, the spool was obtained by welding parts of wires together, which would not be conceivable for an industrial production.
At this step, it is not possible to estimate the production costs of these wires in comparison with standard ones. Further developments of the production of Al-Cu-Li wires would be needed to increase the TRL of this process to enable the industrial production. However, the results of the IAWAS project are a good first step in the definition and production of wires made of Al-Li alloys suitable for WAAM and/or LBW processes.
Concerning the WAAM development with Al-Li wires, a start-up company has been formed for exploitation of the developments of WAAM technology from the WAAMMat programme and other activities at Cranfield University. The results from IAWAS feed directly this commercial initiative as a route for exploitation – particularly to inform end-users about the capability for WAAM to produce Al/Li structures using the new developed wire compositions.
For the developments of the LBW with Al-Li alloys, all results (good results and failures) will be exploited in further projects on Sonaca’s and CRM’s side. For all future parts made of Al-Li, an LBW solution could be considered based on the knowledge acquired during the IAWAS project.

First WAAM walls

WAAM Demonstrator deposition

Final demonstrator