Enhanced mechanical properties of Nb-18.7Si alloy by addition of ceramic nano particles for microstructural control

verfasst von: Elisa Holzmann, Khemais Barienti, Mattia Guglielmi, Egbert Baake, Sebastian Herbst, Hans Jürgen Maier
Abstract: The phase composition, microstructure and mechanical properties of arc-melted eutectic Nb-18.7Si (at.-%) alloys with different nano-ceramic particle addition (Al₂O₃, TiC, SiC, 5 mol.-%) were investigated. The results showed that ceramic Al₂O₃ and TiC nanoparticle are thermally and chemically stable and can be used to tailor phase composition and refine the microstructure, while SiC dissolves completely in the melt. Al₂O₃ and TiC nanoparticle were found mainly in two different areas: (1) at grain boundaries of eutectic structures and (2) on the phase boundaries of silicides inside the eutectics. The presence of the particles refined the microstructure down to nano-scale lamellae by functioning as heterogeneous nuclei for the silicide phase. Without nano particle addition, the Nb-18.7Si alloy was mainly composed of Nb solid solution (Nb_ss) and Nb₃Si. The addition of 5 mol.-% Al₂O₃ promoted the decomposition of the Nb₃Si phase and an ultrafine nano-scale lamellar eutectic structure (Nb_ss + α-Nb₅Si₃) formed. With the addition of 5 mol.-% TiC, primary Nb₃Si and coarse Nb_ss were observed, as well as fine eutectic Nb_ss + γ-Nb₅Si₃ structures. The complete dissolution of SiC led to a hypereutectic alloy with primary Nb₃Si and γ-Nb₅Si₃ phase, coarse Nb_ss and eutectic Nb_ss + γ-Nb₅Si₃ structures. The compressive strength was increased from 3068 MPa to 3446 MPa by adding 5 mol.-% Al₂O₃ due to the formation of the high strength α-Nb₅Si₃ phase, the ultrafine nano-scale lamellar structures of Nb_ss + α-Nb₅Si₃ and the strong interface of Nb_ss/α-Nb₅Si₃. However, the small grain size of the Nb_ss phase was not effective in inhibiting crack propagation. Crack bridging and branching seem to be important mechanisms at the Nb_ss phase to inhibit crack propagation. Therefore, the size and distribution of Nb_ss play a key role. The results indicate that a continuous Nb_ss phase with embedded silicide phase and coarse Nb_ss phases can inhibit crack propagation.
Organisationseinheit(en): Institut für Werkstoffkunde
Institut für Elektroprozesstechnik
Typ: Artikel
Journal: INTERMETALLICS
Band: 176
ISSN: 0966-9795
Publikationsdatum: 22.11.2024
Publikationsstatus: Elektronisch veröffentlicht (E-Pub)
Peer-reviewed: Ja
ASJC Scopus Sachgebiete: Allgemeine Chemie, Werkstoffmechanik, Maschinenbau, Metalle und Legierungen, Werkstoffchemie
Elektronische Version(en): https://doi.org/10.1016/j.intermet.2024.108577 (Zugang: Offen)

BibTeX

@article{237d8b07cdf34e5ab8b8c0e0ea4c348e,
title = "Enhanced mechanical properties of Nb-18.7Si alloy by addition of ceramic nano particles for microstructural control",
abstract = "The phase composition, microstructure and mechanical properties of arc-melted eutectic Nb-18.7Si (at.-%) alloys with different nano-ceramic particle addition (Al2O3, TiC, SiC, 5 mol.-%) were investigated. The results showed that ceramic Al2O3 and TiC nanoparticle are thermally and chemically stable and can be used to tailor phase composition and refine the microstructure, while SiC dissolves completely in the melt. Al2O3 and TiC nanoparticle were found mainly in two different areas: (1) at grain boundaries of eutectic structures and (2) on the phase boundaries of silicides inside the eutectics. The presence of the particles refined the microstructure down to nano-scale lamellae by functioning as heterogeneous nuclei for the silicide phase. Without nano particle addition, the Nb-18.7Si alloy was mainly composed of Nb solid solution (Nbss) and Nb3Si. The addition of 5 mol.-% Al2O3 promoted the decomposition of the Nb3Si phase and an ultrafine nano-scale lamellar eutectic structure (Nbss + α-Nb5Si3) formed. With the addition of 5 mol.-% TiC, primary Nb3Si and coarse Nbss were observed, as well as fine eutectic Nbss + γ-Nb5Si3 structures. The complete dissolution of SiC led to a hypereutectic alloy with primary Nb3Si and γ-Nb5Si3 phase, coarse Nbss and eutectic Nbss + γ-Nb5Si3 structures. The compressive strength was increased from 3068 MPa to 3446 MPa by adding 5 mol.-% Al2O3 due to the formation of the high strength α-Nb5Si3 phase, the ultrafine nano-scale lamellar structures of Nbss + α-Nb5Si3 and the strong interface of Nbss/α-Nb5Si3. However, the small grain size of the Nbss phase was not effective in inhibiting crack propagation. Crack bridging and branching seem to be important mechanisms at the Nbss phase to inhibit crack propagation. Therefore, the size and distribution of Nbss play a key role. The results indicate that a continuous Nbss phase with embedded silicide phase and coarse Nbss phases can inhibit crack propagation.",
keywords = "AlO, Microstructure, Nano ceramic particle, Nb-Si based alloy, SiC, TiC",
author = "Elisa Holzmann and Khemais Barienti and Mattia Guglielmi and Egbert Baake and Sebastian Herbst and Maier, {Hans J{\"u}rgen}",
note = "Publisher Copyright: {\textcopyright} 2024 The Authors",
year = "2024",
month = nov,
day = "22",
doi = "10.1016/j.intermet.2024.108577",
language = "English",
volume = "176",
journal = "INTERMETALLICS",
issn = "0966-9795",
publisher = "Elsevier Ltd.",
}