Chiara Monti


Last Name

Monti

First Name

Chiara

ORCID

0000-0003-1332-0719

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2023 - 20255
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Publications 1 - 5 of 5
  • The beneficial effect of Fe addition on the hot cracking susceptibility and mechanical properties of eutectic AlMgSc alloy processed by powder bed fusion
    Item type: Journal Article
    Turani, Matteo; Monti, Chiara; Spierings, Adriaan B.; et al. (2025)
    Journal of Alloys and Compounds
    This paper presents findings on the positive impact of adding 1.8 wt% of iron to an eutectic AlMgSc alloy processed by laser powder bed fusion. Examination of process parameters reveals that the addition of Fe enhances material processability, reducing susceptibility to hot cracking and enabling the fabrication of crack-free samples with an optical density exceeding 99.8 % on a centimeter scale. From an early stage of solidification (fs ≈ 0.01), intergranular nano-sized Al6(Fe,Mn) particles precipitate alongside the α-Al matrix, their capability in pinning the grain boundaries produces zones characterized by fine grains that hinder the epitaxial growth of large and columnar grains. The refined microstructure can better accommodate thermally induced strains and facilitate liquid backfilling at the terminal stage of solidification, thus limiting hot cracking susceptibility. Moreover, the formation of interdendritic network of Al6(Fe,Mn) particles during the solidification of the central part of the melt pool provides early coalescence of Al dendrites, reducing the time the material spends in a cracking-sensitive state and limiting its tendency to form hot cracks. The formation of the metastable Al6(Fe,Mn) phase, as opposed to the stable Al13Fe4 phase, enhances material strength while preserving ductility. Notably, samples tested perpendicular to the build direction in their as-built conditions achieved a yield strength of 248 ± 2 MPa, an ultimate tensile strength of 406 ± 2 MPa, and an elongation at fracture of 19.6 ± 0.4 %.
  • Microstructure and mechanical properties of AlTiCrFe and AlTiCrCu alloys processed by Laser Powder Bed Fusion
    Item type: Journal Article
    Monti, Chiara; Turani, Matteo; Wierschke, Sebastian; et al. (2024)
    Materials Science and Engineering: A
    Additive manufacturing (AM) of aluminium alloys urges new alloy compositions to meet the requirements for high-strength and processability of the engineering products. This research focuses on the development of two Al alloys, AlTiCrFe and AlTiCrCu, with the goal to exploit the potential of transition element additions for grain refinement and increasing strength. Robust processability and build rates are reached for the two alloys, with no cracks and high density up to 99.8%. AlTiCrFe shows a bimodal microstructure, with the presence of ultrafine and fine grained zones, that can be attributed to a dual precipitation stage. Al3Ti precipitates are present in the ultrafine grained zone, confirming the effectivity of Ti as grain refiner. In addition, Al6Fe precipitates are present in the fine grained region, as a consequence of the later precipitation stage. AlTiCrCu, on the contrary, shows an homogeneous ultrafine grain microstructure, with Cu segregating at the grain boundaries. SAED analyses confirm the phase identification with the presence of high volume density cubic precipitates of Al3Ti_L12. AlTiCrFe and AlTiCrCu exhibit a yield strength value of 363 ± 1 MPa and 340 ± 1 MPa, respectively. These findings indicate that the two alloys open up new possibilities for a novel class of aluminium alloys for AM, leveraging the incorporation of transition elements, which aids in achieving strength during the as-built state, eliminating the requirement for supplementary heat treatment.
  • A new Al-Cu alloy for LPBF developed via ultrasonic atomization
    Item type: Journal Article
    Monti, Chiara; Turani, Matteo; Papis, Konrad J.M.; et al. (2023)
    Materials & Design
    Wrought 2xxx aluminum alloys are difficult to process by laser powder bed fusion (LPBF) because of the hot cracking susceptibility caused by their large solidification range. Although several studies on Ti and Zr additions to 2xxx Al-Cu alloys show improved processability in LPBF, only few explore the addition of alternative alloying elements such as Cr and Fe. There is thus little knowledge on the ability of these elements to avoid hot cracking. In the present work, a new Al-Cu alloy with Ti, Cr and Fe additions is put forward and the mechanisms impeding hot cracking formation are analyzed. (Al, Cr)3Ti_L12 precipitates are formed during the solidification process, promoting heterogenous nucleation and grain refinement. Cr not only contributes to solid solution strengthening but also supports the stabilization of the Al3Ti metastable cubic phase. The addition of near-eutectic Fe decreases the solidification range, further reducing the susceptibility for hot cracking. Nano-hardness mapping reveals the solidification path of the alloy, with higher values associated with the highly dense areas of precipitates forming at the melt pool boundaries. A novel printable alloy with hardness values exceeding those of existing Al alloys for LPBF was designed.
  • Evaluating the use of scrap metal to produce Al-5Cu-3Ti-1Cr-1Fe alloy powder for laser powder bed fusion
    Item type: Journal Article
    Monti, Chiara; Gobber , Federico Simone; Turani , Matteo; et al. (2025)
    Sustainable Materials and Technologies
    This study compares the production of Al-5Cu-3Ti-1Cr-1Fe alloy powders for laser powder bed fusion (PBF-LB/M) using either virgin or recycled and scrap materials as feedstock. As for the latter, three different material sources, namely aluminum 2024, Ti-6Al-4V and AISI 316L, were selected to reproduce the target alloy composition by gas atomization. The feasibility of achieving high-quality alloyed powder from mixed scrap sources was demonstrated, with particular focus on processability, mechanical performance, and environmental impact. Both powders produced from scrap/recycled (Re-Alloy) and virgin (V-Alloy) feedstock materials were processed via PBF-LB/M to compare their printability, and the manufactured samples were tested to evaluate their mechanical properties. The Re-Alloy exhibited a stable PBF-LB/M processability over a wide set of parameters, attributed to the presence of elements like Si and Mg, which improved laser absorptivity. Mechanical testing revealed comparable properties, with the Re-Alloy achieving slightly lower strength but higher elongation at break due to the reduced Fe content. Finally, a life cycle assessment (LCA) analysis quantified the environmental impacts, showing a significant reduction of approximately 50% in the carbon footprint for the Re-Alloy powders (15.5 ± 1.0 kgCO2/kg) compared to the V-Alloy (31.5 ± 1.8 kgCO2/kg). The carbon footprint of the PBF-LB/M process itself was measured at 15.2 ± 1.2 kgCO2/kg of deposited material. This research highlights the potential of using recycled and waste materials to reduce the environmental impact of metal powder production while maintaining technical feasibility. The findings offer a promising approach for enhancing the sustainability of additive manufacturing processes.
Publications 1 - 5 of 5