Microstructural Characterization of AA6061 Versus AA6061 HIP Bonded Cladding–Cladding Interface

Sohn

2020

ACS Comb. Sci.

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alloy exhibited a lower free energy of mixing, i.e., higher thermodynamic stability, than equiatomic Al x CoCrFeNiMn compositions, at 1100 °C and above. Therefore, the role of enthalpy was estimated to be significant in achieving higher thermodynamic stability in off-equiatomic alloys, since they always have lower entropy of mixing than their equiatomic counterparts. The magnitude of interdiffusion coefficients of individual elements in Al−Co−Cr−Fe−Ni−Mn alloys were compared to the interdiffusion coefficients in relevant quinary, quaternary, and ternary solvent-based alloys. Interdiffusion coefficients were not necessarily lower in FCC Al−Co−Cr−Fe−Ni−Mn alloys; therefore no sluggish diffusion was observed in FCC HEA, but diffusion of individual elements in BCC Al−Co−Cr−Fe−Ni−Mn alloy followed the sluggish diffusion hypothesis except for Ni. All compositions in the FCC Al−Co−Cr−Fe−Ni−Mn alloy were observed to comply with existing empirical single phase formation rules in high entropy alloys.

Section: Methodsmentioning

confidence: 99%

High Entropy and Sluggish Diffusion “Core” Effects in Senary FCC Al–Co–Cr–Fe–Ni–Mn Alloys

Sohn

2020

ACS Comb. Sci.

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“…Diffusion couples were then isothermally annealed in an inert environment at a predetermined temperature for a fixed time, and then water-quenched to retained high temperature microstructure. Additional details on the fabrication of diffusion couples can be found elsewhere [14][15][16][17][18][19].…”

Section: Fabrication Of Diffusion Couplesmentioning

confidence: 99%

Fundamental Core Effects in Transition Metal High-Entropy Alloys: “High-Entropy” and “Sluggish Diffusion” Effects

Sohn

2021

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High entropy alloys (HEAs) are equimolar multi-principal-element alloys (MPEAs) that are different from traditional solvent-based multicomponent alloys based on the concept of alloy design. Based on initial work by Yeh and co-workers, HEAs were postulated to exhibit four “core” effects: high entropy, sluggish diffusion, lattice distortion, and cocktail effect. Out of these four proposed core effects, “high entropy” and “sluggish diffusion” effects were most debated in the literature as these core effects directly affect the thermodynamic and kinetic understanding of HEAs. The initial work on HEAs by several researchers utilized these effects to indirectly support the experimentally observed “unique” properties, without independent investigation of these core effects. The presumed implications of these core effects resulted in justification or generalization of properties to all HEAs, e.g., all HEAs should exhibit high temperature stability based on high entropy effect, high temperature strength owing to limited grain growth, good diffusion barrier application due to sluggish diffusion kinetics, etc. However, many recent studies have challenged these core effects, and suggested that not all HEAs were observed to exhibit these core effects.

“…Preliminary characterization of claddingcladding interface in monolithic fuel plates performed by Jue et al [14] demonstrated that the interface is typically rich in discontinuous precipitates containing Mg, O and Si, aligned along the interfacial bond line. Mehta et al [27] carried out comprehensive characterization of the claddingcladding interface. Figure 3…”

Section: Interdiffusion and Reactions With Aa6061mentioning

confidence: 99%

Interdiffusion, Reactions, and Phase Transformations Observed during Fabrication of Low Enriched Uranium Monolithic Fuel System for Research and Test Reactors

Newell

Park

et al. 2018

DDF

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Monolithic fuel plates have been developed utilizing low enriched U alloyed with 10 wt.% Mo to replace highly enriched fuels in research and test reactors, in accordance with the goals of the Materials Management and Minimization Reactor Conversion Program. The fuel plates consist of U10Mo fuel, Zr diffusion barrier, and AA6061 cladding. They are fabricated by co-rolling the U10Mo and Zr, which are then encapsulated via hot isostatic pressing of the entire U10Mo/Zr/AA6061 assembly. During fabrication, the metal constituents of the fuel plates undergo phase transformations as well as interdiffusion and reactions at interfaces. The areas of interest are the U10Mo fuel, U10Mo/Zr interface, U10Mo/AA6061 interface, Zr/AA6061 interface, and AA6061-AA6061 bond line. Knowledge of the transformations and growth in the plates is necessary to optimize fabrication parameters and predict behavior as they relate to irradiation performance. Numerous studies have been conducted to analyze these reactions in monolithic fuel plates, and a summary of their observations is provided in this paper.