Cargando…

On the Microstructure and Properties of Nb-18Si-6Mo-5Al-5Cr-2.5W-1Hf Nb-Silicide Based Alloys with Ge, Sn and Ti Additions (at.%)

We studied the microstructures and isothermal oxidation of the Nb-silicide-based alloys Nb-11.5Ti-18Si-5Mo-2W-4.9Sn-4.6Ge-4.5Cr-4.7Al-1Hf (JZ4) and Nb-21Ti-18Si-6.7Mo-1.2W-4.4Sn-4.2Ge-4Cr-3.7Al-0.8Hf (JZ5), calculated their average creep rate for the creep goal conditions of T = 1200 °C and σ = 170...

Descripción completa

Detalles Bibliográficos
Autores principales: Zhao, Jiang, Utton, Claire, Tsakiropoulos, Panos
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7602085/
https://www.ncbi.nlm.nih.gov/pubmed/33066311
http://dx.doi.org/10.3390/ma13204548
_version_ 1783603588067491840
author Zhao, Jiang
Utton, Claire
Tsakiropoulos, Panos
author_facet Zhao, Jiang
Utton, Claire
Tsakiropoulos, Panos
author_sort Zhao, Jiang
collection PubMed
description We studied the microstructures and isothermal oxidation of the Nb-silicide-based alloys Nb-11.5Ti-18Si-5Mo-2W-4.9Sn-4.6Ge-4.5Cr-4.7Al-1Hf (JZ4) and Nb-21Ti-18Si-6.7Mo-1.2W-4.4Sn-4.2Ge-4Cr-3.7Al-0.8Hf (JZ5), calculated their average creep rate for the creep goal conditions of T = 1200 °C and σ = 170 MPa, and compared properties of the two alloys with those of other refractory metal (RM) complex concentrated alloys (RCCAs). Both alloys had a density less than 7.3 g/cm(3) and lower than the density of multiphase bcc solid solution + M(5)Si(3) silicide RCCAs. There was macrosegregation of Si in both alloys, which had the same phases in their as-cast microstructures, namely βNb(5)Si(3), αNb(5)Si(3), A15-Nb(3)X (X = Al, Ge, Si, Sn), TM(5)Sn(2)X (X = Al, Ge, Si), C14-Cr(2)Nb, but no solid solution. After heat treatment at 1500 °C for 100 h, a low volume fraction of a W-rich (Nb, W)(ss) solid solution was observed in both alloys together with βNb(5)Si(3), αNb(5)Si(3) and A15-Nb(3)X but not the TM(5)Sn(2)X, whereas the Laves phase was observed only in JZ4. At 800 °C, both alloys did not pest, and there was no spallation of their scales at 1200 °C. At both temperatures, both alloys followed parabolic oxidation kinetics and their weight changes were lower than those of Ti-rich Nb-silicide-based alloys. The oxidation of both alloys was superior to that of other RCCAs studied to date. For each alloy the Si macrosegregation, volume fraction of solid solution, chemical composition of solid solution and Nb(5)Si(3), and weight changes in isothermal oxidation at 800 and 1200 °C that were calculated using the alloy design methodology NICE agreed well with the experimental results.
format Online
Article
Text
id pubmed-7602085
institution National Center for Biotechnology Information
language English
publishDate 2020
publisher MDPI
record_format MEDLINE/PubMed
spelling pubmed-76020852020-11-01 On the Microstructure and Properties of Nb-18Si-6Mo-5Al-5Cr-2.5W-1Hf Nb-Silicide Based Alloys with Ge, Sn and Ti Additions (at.%) Zhao, Jiang Utton, Claire Tsakiropoulos, Panos Materials (Basel) Article We studied the microstructures and isothermal oxidation of the Nb-silicide-based alloys Nb-11.5Ti-18Si-5Mo-2W-4.9Sn-4.6Ge-4.5Cr-4.7Al-1Hf (JZ4) and Nb-21Ti-18Si-6.7Mo-1.2W-4.4Sn-4.2Ge-4Cr-3.7Al-0.8Hf (JZ5), calculated their average creep rate for the creep goal conditions of T = 1200 °C and σ = 170 MPa, and compared properties of the two alloys with those of other refractory metal (RM) complex concentrated alloys (RCCAs). Both alloys had a density less than 7.3 g/cm(3) and lower than the density of multiphase bcc solid solution + M(5)Si(3) silicide RCCAs. There was macrosegregation of Si in both alloys, which had the same phases in their as-cast microstructures, namely βNb(5)Si(3), αNb(5)Si(3), A15-Nb(3)X (X = Al, Ge, Si, Sn), TM(5)Sn(2)X (X = Al, Ge, Si), C14-Cr(2)Nb, but no solid solution. After heat treatment at 1500 °C for 100 h, a low volume fraction of a W-rich (Nb, W)(ss) solid solution was observed in both alloys together with βNb(5)Si(3), αNb(5)Si(3) and A15-Nb(3)X but not the TM(5)Sn(2)X, whereas the Laves phase was observed only in JZ4. At 800 °C, both alloys did not pest, and there was no spallation of their scales at 1200 °C. At both temperatures, both alloys followed parabolic oxidation kinetics and their weight changes were lower than those of Ti-rich Nb-silicide-based alloys. The oxidation of both alloys was superior to that of other RCCAs studied to date. For each alloy the Si macrosegregation, volume fraction of solid solution, chemical composition of solid solution and Nb(5)Si(3), and weight changes in isothermal oxidation at 800 and 1200 °C that were calculated using the alloy design methodology NICE agreed well with the experimental results. MDPI 2020-10-13 /pmc/articles/PMC7602085/ /pubmed/33066311 http://dx.doi.org/10.3390/ma13204548 Text en © 2020 by the authors. 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
Zhao, Jiang
Utton, Claire
Tsakiropoulos, Panos
On the Microstructure and Properties of Nb-18Si-6Mo-5Al-5Cr-2.5W-1Hf Nb-Silicide Based Alloys with Ge, Sn and Ti Additions (at.%)
title On the Microstructure and Properties of Nb-18Si-6Mo-5Al-5Cr-2.5W-1Hf Nb-Silicide Based Alloys with Ge, Sn and Ti Additions (at.%)
title_full On the Microstructure and Properties of Nb-18Si-6Mo-5Al-5Cr-2.5W-1Hf Nb-Silicide Based Alloys with Ge, Sn and Ti Additions (at.%)
title_fullStr On the Microstructure and Properties of Nb-18Si-6Mo-5Al-5Cr-2.5W-1Hf Nb-Silicide Based Alloys with Ge, Sn and Ti Additions (at.%)
title_full_unstemmed On the Microstructure and Properties of Nb-18Si-6Mo-5Al-5Cr-2.5W-1Hf Nb-Silicide Based Alloys with Ge, Sn and Ti Additions (at.%)
title_short On the Microstructure and Properties of Nb-18Si-6Mo-5Al-5Cr-2.5W-1Hf Nb-Silicide Based Alloys with Ge, Sn and Ti Additions (at.%)
title_sort on the microstructure and properties of nb-18si-6mo-5al-5cr-2.5w-1hf nb-silicide based alloys with ge, sn and ti additions (at.%)
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7602085/
https://www.ncbi.nlm.nih.gov/pubmed/33066311
http://dx.doi.org/10.3390/ma13204548
work_keys_str_mv AT zhaojiang onthemicrostructureandpropertiesofnb18si6mo5al5cr25w1hfnbsilicidebasedalloyswithgesnandtiadditionsat
AT uttonclaire onthemicrostructureandpropertiesofnb18si6mo5al5cr25w1hfnbsilicidebasedalloyswithgesnandtiadditionsat
AT tsakiropoulospanos onthemicrostructureandpropertiesofnb18si6mo5al5cr25w1hfnbsilicidebasedalloyswithgesnandtiadditionsat