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On the Alloying and Properties of Tetragonal Nb(5)Si(3) in Nb-Silicide Based Alloys
The alloying of Nb(5)Si(3) modifies its properties. Actual compositions of (Nb,TM)(5)X(3) silicides in developmental alloys, where X = Al + B + Ge + Si + Sn and TM is a transition and/or refractory metal, were used to calculate the composition weighted differences in electronegativity (Δχ) and an av...
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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MDPI
2018
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5793567/ https://www.ncbi.nlm.nih.gov/pubmed/29300327 http://dx.doi.org/10.3390/ma11010069 |
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author | Tsakiropoulos, Panos |
author_facet | Tsakiropoulos, Panos |
author_sort | Tsakiropoulos, Panos |
collection | PubMed |
description | The alloying of Nb(5)Si(3) modifies its properties. Actual compositions of (Nb,TM)(5)X(3) silicides in developmental alloys, where X = Al + B + Ge + Si + Sn and TM is a transition and/or refractory metal, were used to calculate the composition weighted differences in electronegativity (Δχ) and an average valence electron concentration (VEC) and the solubility range of X to study the alloying and properties of the silicide. The calculations gave 4.11 < VEC < 4.45, 0.103 < Δχ < 0.415 and 33.6 < X < 41.6 at.%. In the silicide in Nb-24Ti-18Si-5Al-5Cr alloys with single addition of 5 at.% B, Ge, Hf, Mo, Sn and Ta, the solubility range of X decreased compared with the unalloyed Nb(5)Si(3) or exceeded 40.5 at.% when B was with Hf or Mo or Sn and the Δχ decreased with increasing X. The Ge concentration increased with increasing Ti and the Hf concentration increased and decreased with increasing Ti or Nb respectively. The B and Sn concentrations respectively decreased and increased with increasing Ti and also depended on other additions in the silicide. The concentration of Sn was related to VEC and the concentrations of B and Ge were related to Δχ. The alloying of Nb(5)Si(3) was demonstrated in Δχ versus VEC maps. Effects of alloying on the coefficient of thermal expansion (CTE) anisotropy, Young’s modulus, hardness and creep data were discussed. Compared with the hardness of binary Nb(5)Si(3) (1360 HV), the hardness increased in silicides with Ge and dropped below 1360 HV when Al, B and Sn were present without Ge. The Al effect on hardness depended on other elements substituting Si. Sn reduced the hardness. Ti or Hf reduced the hardness more than Cr in Nb(5)Si(3) without Ge. The (Nb,Hf)(5)(Si,Al)(3) had the lowest hardness. VEC differentiated the effects of additions on the hardness of Nb(5)Si(3) alloyed with Ge. Deterioration of the creep of alloyed Nb(5)Si(3) was accompanied by decrease of VEC and increase or decrease of Δχ depending on alloying addition(s). |
format | Online Article Text |
id | pubmed-5793567 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-57935672018-02-07 On the Alloying and Properties of Tetragonal Nb(5)Si(3) in Nb-Silicide Based Alloys Tsakiropoulos, Panos Materials (Basel) Article The alloying of Nb(5)Si(3) modifies its properties. Actual compositions of (Nb,TM)(5)X(3) silicides in developmental alloys, where X = Al + B + Ge + Si + Sn and TM is a transition and/or refractory metal, were used to calculate the composition weighted differences in electronegativity (Δχ) and an average valence electron concentration (VEC) and the solubility range of X to study the alloying and properties of the silicide. The calculations gave 4.11 < VEC < 4.45, 0.103 < Δχ < 0.415 and 33.6 < X < 41.6 at.%. In the silicide in Nb-24Ti-18Si-5Al-5Cr alloys with single addition of 5 at.% B, Ge, Hf, Mo, Sn and Ta, the solubility range of X decreased compared with the unalloyed Nb(5)Si(3) or exceeded 40.5 at.% when B was with Hf or Mo or Sn and the Δχ decreased with increasing X. The Ge concentration increased with increasing Ti and the Hf concentration increased and decreased with increasing Ti or Nb respectively. The B and Sn concentrations respectively decreased and increased with increasing Ti and also depended on other additions in the silicide. The concentration of Sn was related to VEC and the concentrations of B and Ge were related to Δχ. The alloying of Nb(5)Si(3) was demonstrated in Δχ versus VEC maps. Effects of alloying on the coefficient of thermal expansion (CTE) anisotropy, Young’s modulus, hardness and creep data were discussed. Compared with the hardness of binary Nb(5)Si(3) (1360 HV), the hardness increased in silicides with Ge and dropped below 1360 HV when Al, B and Sn were present without Ge. The Al effect on hardness depended on other elements substituting Si. Sn reduced the hardness. Ti or Hf reduced the hardness more than Cr in Nb(5)Si(3) without Ge. The (Nb,Hf)(5)(Si,Al)(3) had the lowest hardness. VEC differentiated the effects of additions on the hardness of Nb(5)Si(3) alloyed with Ge. Deterioration of the creep of alloyed Nb(5)Si(3) was accompanied by decrease of VEC and increase or decrease of Δχ depending on alloying addition(s). MDPI 2018-01-04 /pmc/articles/PMC5793567/ /pubmed/29300327 http://dx.doi.org/10.3390/ma11010069 Text en © 2018 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Tsakiropoulos, Panos On the Alloying and Properties of Tetragonal Nb(5)Si(3) in Nb-Silicide Based Alloys |
title | On the Alloying and Properties of Tetragonal Nb(5)Si(3) in Nb-Silicide Based Alloys |
title_full | On the Alloying and Properties of Tetragonal Nb(5)Si(3) in Nb-Silicide Based Alloys |
title_fullStr | On the Alloying and Properties of Tetragonal Nb(5)Si(3) in Nb-Silicide Based Alloys |
title_full_unstemmed | On the Alloying and Properties of Tetragonal Nb(5)Si(3) in Nb-Silicide Based Alloys |
title_short | On the Alloying and Properties of Tetragonal Nb(5)Si(3) in Nb-Silicide Based Alloys |
title_sort | on the alloying and properties of tetragonal nb(5)si(3) in nb-silicide based alloys |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5793567/ https://www.ncbi.nlm.nih.gov/pubmed/29300327 http://dx.doi.org/10.3390/ma11010069 |
work_keys_str_mv | AT tsakiropoulospanos onthealloyingandpropertiesoftetragonalnb5si3innbsilicidebasedalloys |