Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - AlForAMA (Innovative Al alloy For aircraft structural parts using Additive MAnufacturing technology)

Teaser

There is a need in aeronautic industry to develop innovative high performance aluminum alloys feasible by powder metallurgy and to develop additive manufacturing processes for such alloys while obtaining the requested characteristics in terms of mechanical strength and...

Summary

There is a need in aeronautic industry to develop innovative high performance aluminum alloys feasible by powder metallurgy and to develop additive manufacturing processes for such alloys while obtaining the requested characteristics in terms of mechanical strength and corrosion resistance. Such developments aim at developing lighter structures that will contribute in further reductions in fuel consumption, CO2 and NOx emissions.
The main goal of the AlForAMA project is to develop an innovative High Strength Al alloy, feasible by powder metallurgy and suitable for Selective Laser Melting (SLM), with improved weldability and increased mechanical and corrosion resistance in comparison to cast grades Al alloys currently employed in Additive Manufacturing (AM).
The specific technical objectives of the project are:
1. To design the chemical composition of innovative High strength Al alloys that potentially meet the specifications required in terms of mechanical strength and corrosion resistance.
2. To develop a gas atomization process to obtain an Al powder with the new developed chemical composition and suitable for AM manufacturing regarding particle morphology and Particle size distribution
3. To develop a mixing process to ensure the preparation of a homogeneous powder mixture with sufficiently high flowability.
4. To define the most critical variables (heat input, layer thickness, hatch distance, scanning pattern, laser spot, beam shape) for an optimized SLM process, and the corresponding process control strategy, both to ensure defect free material manufacturing.
5. To carry-out a thermal treatment optimization, taking into account the initial condition of the material, to improve the mechanical performances and corrosion resistance of the innovative alloy.
6. To implement thermodynamic analysis methodologies for tailoring new Al alloys in order to improve the phase structure during AM processing and subsequent heat treatment.
7. To investigate the SLM material behaviour before and after heat treatment, with and without surface machining by means of the following tests: quasi static tensile strength testing as well as fatigue testing, metallographic microstructure structure and chemical composition analysis, and galvanic compatibility.
8. To validate the developed SLM and heat treatment methodology for one user case. A demonstrator part, designed by the topic manager, will be manufactured by SLM, thermally treated, inspected and tested in order to compare with coupon level results.

Work performed

WP1 addresses the definition of innovative high strength aluminum alloys to be produced during ALFORAMA project. Thus, two main approaches to obtain high strength aluminum alloys for SLM processing were explored:
(1) Start from conventionally used high strength Al alloys (7xxx series) and improve their SLM processability by alloy modification in order to reduce the cracking susceptibility by decreasing the thermal solidification range and refining the microstructure.
(2) Start from currently SLM processable Al alloys and improve their mechanical properties by adding (a) elements to promote hardening by intermetallic precipitates after appropriate heat treatments or (b) ceramic particles such as carbides (SiC, B4C…) or borides (TiB2) which can act as nucleants to induce microstructure refinement and, consequently, increase in hardness.
The evaluation of advantages, drawbacks, risks and constraints of each proposed approach was performed before making a final selection. Four approaches have been selected to develop an innovative high strength Al alloy for aeronautic applications: two based on 7xxx series Al alloys, adding 4wt% of Si and 0.5-1.5wt%of Zr in order to improve the processability of the original alloy, and two other approaches, based on AlSi10Mg alloy, adding 4wt% of Cu and 4-8wt% of TiB2 particles, in order to improve the mechanical properties.
All approaches were produced by atomization process. Semi-industrial atomization (up to 1 Kg) was also used for powder manufacturing. The powders were processed by SLM and the optimal processing parameters were achieved.
A crack free 7075 Al alloy was obtained after SLM processing by adding 4wt% of Si to the original composition. The original Zn and Mg content were modified in order to compensate for their evaporation during the SLM process.
The mechanical performance of the AlSi10Mg alloy has been improved at room temperature by the addition of 4wt% of Cu. After optimizing the heat treatment, a hardness value comparable to the 7075 Al alloy, was achieved for this new alloy.

Final results

ALFORAMA aims at developing a new requested material to respond to the lightness requirements and thus be compliant with the environmental demands. This will contribute to reinforce the European aeronautic industry to keep at the forefront of the sector.
The main outcomes (foreground) considered as unconventional methodologies and innovations to supporting the industrial impacts and that were generated now are:
• Know-how on design of alloys for additive manufacturing
• Powder atomization technology of light Aluminum alloys developed with tailored and improved final properties
• Definition of the optimized powder characteristics, both in terms of powder composition and morphology to optimize the SLM processing of particle reinforced Al alloys
• Computational methodology, including thermodynamic and kinetic calculations, to optimize Al based metal alloys compositions that are more suitable for SLM processing
• Development of SLM processing for innovative High Strength Al alloys with improved mechanical and corrosion properties compared to conventional cast grades alloys
• Defining a protocol for optimization of heat treatments of new Al alloys, with tailored composition, in order to improve final mechanical properties.

Website & more info

More info: http://www.alforama.eu/.