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Synthesis and characterization of (Al,Si)₃(Zr,Ti)-D0₂₂/D0₂₃ intermetallics: Understanding the stability of silicon substitution

Juan-Ricardo Castillo-Sánchez, Georges Salloum-Abou-Jaoude, Aïmen E. Gheribi, Paul Lafaye, Kentaro Oishi, Jean-Philippe Masse, Étienne Bousser, Gilles L'Espérance and Jean-Philippe Harvey

Article (2024)

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Abstract

(Al,Si)₃(Zr,Ti)-D0₂₂/D0₂₃ are phases that may form in aerospace and automotive aluminium alloys. The substitution of Zr/Ti in these solid solutions is widely reported in the literature; however, it remains relatively unexplored for Si. In this work, in situ precipitation of (Al,Si)₃(Zr,Ti)-D0₂₂/D0₂₃ intermetallics was performed using Al-Si-Zr-Ti alloys. The precipitation, sedimentation and concentration of numerous intermetallic particles were accomplished by filtrating the residual molten aluminium using a temperature/pressure-controlled vessel adapted with a PoDFA filter. A combination of SEM, TEM, XRD and EMP analysis allowed the identification of (Al,Si)₃(Zr,Ti)-D0₂₂/D0₂₃ intermetallics concentrated within α-FCC matrices of non-Si-doped (sample S2) and Si-doped (samples S4 and S6) alloys. EDS analysis confirmed that Zr and Ti substitute each other in the D0₂₂ and D0₂₃ phases, whereas Si substitutes in Al sites. Acceptance of Si inside the D0₂₃ phase was not expected according to FTlite (FactSage) and TCAL7 (Thermo-Calc) databases. Additionally, Si was found to enhance the formation of (Al,Si)₃(Zr,Ti)-D0₂₂ intermetallics with high Zr-content, contrary to FactSage 7.3 predictions. TEM results showed intermetallic/FCC crystal coherency for samples S2 and S6, implying that these intermetallics acted as nucleation sites for the Al-phase due to their small lattice mismatch. Furthermore, Si site occupancy was calculated for both (Al,Si)Ti-D0₂₂ and (Al,Si)₃Zr-D0₂₃ phases via DFT, showing that sites 2b and 4e are the most favorable for Si occupation, respectively. Finally, a thermodynamic model is derived to describe Si substitution upon solidification. Experimental and numerical examinations indicate that Si substitution preferentially occurs in the D0₂₂ intermetallics compared to the D0₂₃ phase.

Uncontrolled Keywords

Intermetallics; PoDFA; Silicon substitution; Aluminium alloys; Grain refiner; DFT simulations; Phase coherency

Additional Information: The following is the Supplementary material related to this article: https://ars.els-cdn.com/content/image/1-s2.0-S1359645423007851-mmc1.pdf
Department: Department of Chemical Engineering
Department of Mathematics and Industrial Engineering
Research Center: (CM)² - Centre for Characterization and Microscopy of Materials
CRCT - Centre for Research in Computational Thermochemistry
Funders: CRSNG/NSERC, Consortium de recherche et d'innovation en transformation métallique (CRITM)
Grant number: ALLRP 560998-2020, 13-2019-056
PolyPublie URL: https://publications.polymtl.ca/56702/
Journal Title: Acta Materialia (vol. 262)
Publisher: Elsevier BV
DOI: 10.1016/j.actamat.2023.119455
Official URL: https://doi.org/10.1016/j.actamat.2023.119455
Date Deposited: 23 Jan 2024 16:05
Last Modified: 23 May 2024 12:39
Cite in APA 7: Castillo-Sánchez, J.-R., Salloum-Abou-Jaoude, G., Gheribi, A. E., Lafaye, P., Oishi, K., Masse, J.-P., Bousser, É., L'Espérance, G., & Harvey, J.-P. (2024). Synthesis and characterization of (Al,Si)₃(Zr,Ti)-D0₂₂/D0₂₃ intermetallics: Understanding the stability of silicon substitution. Acta Materialia, 262, 119455 (18 pages). https://doi.org/10.1016/j.actamat.2023.119455

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