Additive manufacturing of high-strength aluminium alloys for thermal management applications

Careri, Francesco ORCID: 0000-0003-0894-3794 (2025). Additive manufacturing of high-strength aluminium alloys for thermal management applications. University of Birmingham. Ph.D.

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Abstract

The application of Additive Manufacturing (AM) has demonstrated significant potential in developing complex geometries. With its ability to process a wide range of materials, AM technologies have unlocked unprecedented opportunities for designing high-performance components across several sectors. In aerospace applications, the use of AM, and in particular Laser Powder Bed Fusion (L-PBF), for high-strength Aluminium (Al) alloys offers promising solutions to meet structural and thermal management requirements, including improved efficiency, reduced weight and tailored properties. This doctoral research focuses on advancing L-PBF technologies and optimising high-strength Al alloy materials for innovative thermal management solutions for the aerospace sector.
The study focused initially on optimising L-PBF process parameters for novel thin-walled structures for Heat Exchangers (HXs). Machine Learning (ML) algorithms, such as Neural Networks (NN), were applied to optimise important process parameters, identifying the complex relationships between parameters and properties, and minimising time-intensive experimental campaigns. The optimised parameters enabled the successful manufacture of a novel HX design, demonstrating the feasibility of ML-driven optimisation approaches for aerospace thermal systems. Microstructural and surface quality analyses revealed enhanced accuracy and a defect-free microstructure, mitigating leakage risks and failure during operation.
Furthermore, since post-processing is crucial for additively manufactured high-strength Al alloys in aerospace applications, the development of tailored heat treatments (HTs) of high-strength Al alloys was carried out. A novel HT was developed for the high-strength A205 Al alloy, and the obtained microstructure and mechanical properties were compared to the Standard T7 HT and a Commercial HT. A significant reduction in grain size of Rapid HT and Commercial HT compared to the Standard T7 HT was found. The results showed a higher presence of finer Ω-Al2Cu and ϑ'-Al2Cu precipitates for the Rapid HT than the other HTs, achieving a tensile strength of 465 MPa, compared to the Standard T7 HT (422 MPa) and Commercial HT (449 MPa). Fatigue tests at room temperature and creep tests at 180 °C further confirmed a significant improvement in performance of the newly developed Rapid HT. Finally, mechanical properties were analysed using a strengthening mechanism model to link precipitate formation to observed behaviour.
In addition, a post-processing surface treatment was studied to address the requirements in tribological and corrosion performance of high-strength Al alloys, A205 and AlSi10Mg, in severe environments. In particular, Plasma Electrolytic Oxidation (PEO), was applied to the two investigated alloys produced using L-PBF. The PEO coatings were produced on as-received and polished surfaces. The results demonstrated significant improvements in tribological and corrosion resistance of the coated surface, particularly for pre-treatment surfaces, highlighting the importance of surface preparation for optimising performance.
Finally, an interdisciplinary study was conducted, implementing a novel ML model to optimise the L-PBF process strategy for minimising porosity. A Reinforcement Learning (RL) framework, incorporating thermal modelling principles, accurately identified optimal parameter combinations to reduce defects in the A205 Al alloy. This ML approach reduced reliance on extensive experimental data and simulations. Experimental validation confirmed the effectiveness of the RL approach in improving the reliability of L-PBF processes for high-strength aluminium alloys.
This research demonstrated the potential of combining advanced manufacturing, ML-driven optimisation, and tailored post-processing to enhance the performance of high-strength Al components for aerospace applications, addressing challenges in structural integrity, thermal efficiency, and durability.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):