Basic Strengthening Mechanisms in Refractory Metals

Wilcox, B. A.

doi:10.1007/978-1-4684-9120-3_1

Cited by 19 publications

(2 citation statements)

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“…Contamination of RMs and RM alloys by interstitials is well known [ 1 , 2 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ] as is the pest oxidation phenomenon for RM alloys and compounds [ 27 , 28 , 29 , 30 , 31 , 34 , 35 ]. Nb-silicide-based alloys and RCCAs can suffer from pest oxidation and interstitial contamination [ 1 , 20 ].…”

Section: Introductionmentioning

confidence: 99%

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.%)

2020

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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/cm3 and lower than the density of multiphase bcc solid solution + M5Si3 silicide RCCAs. There was macrosegregation of Si in both alloys, which had the same phases in their as-cast microstructures, namely βNb5Si3, αNb5Si3, A15-Nb3X (X = Al, Ge, Si, Sn), TM5Sn2X (X = Al, Ge, Si), C14-Cr2Nb, 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 βNb5Si3, αNb5Si3 and A15-Nb3X but not the TM5Sn2X, 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 Nb5Si3, 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.

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Section: Introductionmentioning

confidence: 99%

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.%)

2020

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“…Among these, niobium is a promising candidate as a turbine material due to its high melting point, low density, high room temperature ductility, and low ductile to brittle temperature [2]. High-temperature, high-strength Nb-based alloys can be realized by adding suitable alloying elements which can provide a solid solution, dispersion, and multiphase strengthening, as well known in the physical metallurgy of refractory alloys [3,4]. However, these alloying elements yield a huge compositional design space.…”

Section: Introductionmentioning

confidence: 99%

Machine learning guided optimal composition selection of niobium alloys for high temperature applications

Mohanty

Chandran

Sparks

2022

Preprint

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Nickel and Cobalt based superalloys are commonly used as turbine materials for high-temperature applications. However, their maximum operating temperature is limited to about 1100oC. Therefore, to improve turbine efficiency, current research is focused on designing materials that can withstand higher temperatures. Niobium-based alloys can be considered as promising candidates because of their exceptional properties at elevated temperatures. The conventional approach to alloy design relies on phase diagrams and structure-property data of limited alloys and extrapolates this information into the unexplored compositional space. In the present work, we harness machine learning and provide a design strategy for finding an Nb-based alloy composition with optimized yield strength and ultimate tensile strength at high temperatures. We use a Bayesian optimization algorithm combined with domain knowledge-based material descriptors to find an optimal Nb-based quaternary and quinary alloy composition for the targeted value of mechanical strengths. Furthermore, we extend our study to multi-objective optimization to suggest an optimal alloy candidate by integrating yield strength and ultimate tensile strength into a single composite property. We developed a detailed design flow and python programming code, which could be helpful for accelerating alloy design in a limited alloy data regime.

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Refractory Metals and Their Alloys

Pink

Eck

2006

Materials Science and Technology

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Basic Strengthening Mechanisms in Refractory Metals

Cited by 19 publications

References 20 publications

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.%)

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.%)

Machine learning guided optimal composition selection of niobium alloys for high temperature applications

Refractory Metals and Their Alloys

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