Microstructural Degradation of the AlMo0.5NbTa0.5TiZr Refractory Metal High-Entropy Superalloy at Elevated Temperatures

Whitfield, Tamsin; Stone, H.J.; Jones, C.N.; Jones, Nicholas

doi:10.3390/e23010080

Cited by 26 publications

(2 citation statements)

References 29 publications

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“…According to Whitfield et al (2021b), both Ni-based and HESAs contain two crystallographically-related phases, however, the arrangement of their phases and their crystal systems differ and the HESAs have been reported to be 84% cheaper than commercial Ni-based superalloy (Chen et al , 2020). The HESA phase is also based on the ordered BCC system, whilst the Ni-based superalloy has a disordered ductile FCC crystal structure with an ordered L1 2 superlattice structure.…”

Section: Advances In Materials Technology: High Entropy Materialsmentioning

confidence: 99%

Recent advances of high entropy alloys for aerospace applications: a review

Dada

Popoola

Mathe

2021

WJE

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Purpose This study aims to review the recent advancements in high entropy alloys (HEAs) called high entropy materials, including high entropy superalloys which are current potential alternatives to nickel superalloys for gas turbine applications. Understandings of the laser surface modification techniques of the HEA are discussed whilst future recommendations and remedies to manufacturing challenges via laser are outlined. Design/methodology/approach Materials used for high-pressure gas turbine engine applications must be able to withstand severe environmentally induced degradation, mechanical, thermal loads and general extreme conditions caused by hot corrosive gases, high-temperature oxidation and stress. Over the years, Nickel-based superalloys with elevated temperature rupture and creep resistance, excellent lifetime expectancy and solution strengthening L12 and γ´ precipitate used for turbine engine applications. However, the superalloy’s density, low creep strength, poor thermal conductivity, difficulty in machining and low fatigue resistance demands the innovation of new advanced materials. Findings HEAs is one of the most frequently investigated advanced materials, attributed to their configurational complexity and properties reported to exceed conventional materials. Thus, owing to their characteristic feature of the high entropy effect, several other materials have emerged to become potential solutions for several functional and structural applications in the aerospace industry. In a previous study, research contributions show that defects are associated with conventional manufacturing processes of HEAs; therefore, this study investigates new advances in the laser-based manufacturing and surface modification techniques of HEA. Research limitations/implications The AlxCoCrCuFeNi HEA system, particularly the Al0.5CoCrCuFeNi HEA has been extensively studied, attributed to its mechanical and physical properties exceeding that of pure metals for aerospace turbine engine applications and the advances in the fabrication and surface modification processes of the alloy was outlined to show the latest developments focusing only on laser-based manufacturing processing due to its many advantages. Originality/value It is evident that high entropy materials are a potential innovative alternative to conventional superalloys for turbine engine applications via laser additive manufacturing.

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Section: Advances In Materials Technology: High Entropy Materialsmentioning

confidence: 99%

Recent advances of high entropy alloys for aerospace applications: a review

Dada

Popoola

Mathe

2021

WJE

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“…The nano-scale microstructures in RSAs are believed to form via a spinodal decomposition during cooling to produce two coherent bcc phases, one of which undergoes an ordering transition to form the B2 phase [5,8,10,13,14]. Spinodal decomposition occurs when the second derivative of the Gibbs energy curve with composition within a miscibility gap is negative.…”

Section: Introductionmentioning

confidence: 99%

An Investigation of the Miscibility Gap Controlling Phase Formation in Refractory Metal High Entropy Superalloys via the Ti-Nb-Zr Constituent System

Whitfield

Wise

Pickering

et al. 2021

Metals

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Refractory metal high entropy superalloys (RSAs) have been heralded as potential new high temperature structural materials. They have nanoscale cuboidal bcc+B2 microstructures that are thought to form on quenching through a spinodal decomposition process driven by the Ta-Zr or Nb-Zr miscibility gaps, followed by ordering of one of the bcc phases. However, it is difficult to isolate the role of different elemental interactions within compositionally complex RSAs. Therefore, in this work the microstructures produced by the Nb-Zr miscibility gap within the compositionally simpler Ti-Nb-Zr constituent system were investigated. A systematic series of alloys with compositions of Ti5NbxZr95−x (x = 25–85 at.%) was studied following quenching from solution heat treatment and long duration thermal exposures at 1000, 900 and 700 °C for 1000 h. During exposures at 900 °C and above the alloys resided in a single bcc phase field. At 700 °C, alloys with 40–75 at.% Nb resided within a three phase bcc + bcc + hcp phase field and a large misfit, 4.7–5%, was present between the two bcc phases. Evidence of nanoscale cuboidal microstructures was not observed, even in slow cooled samples. Whilst it was not possible to conclusively determine whether a spinodal decomposition occurs within this ternary system, these insights suggest that Nb-Zr interactions may not play a significant role in the formation of the nanoscale cuboidal RSA microstructures during cooling.

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On the Thermodynamics and Phase Transformation Pathways in BCC-B2 Refractory Compositionally Complex Superalloys

Lass

2022

Metall Mater Trans A

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Microstructural Degradation of the AlMo0.5NbTa0.5TiZr Refractory Metal High-Entropy Superalloy at Elevated Temperatures

Cited by 26 publications

References 29 publications

Recent advances of high entropy alloys for aerospace applications: a review

Recent advances of high entropy alloys for aerospace applications: a review

An Investigation of the Miscibility Gap Controlling Phase Formation in Refractory Metal High Entropy Superalloys via the Ti-Nb-Zr Constituent System

On the Thermodynamics and Phase Transformation Pathways in BCC-B2 Refractory Compositionally Complex Superalloys

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