Effects of Marker Size and Distribution on the Development of Kirkendall Voids, and Coefficients of Interdiffusion and Intrinsic Diffusion

Schulz, Esin; Mehta, Abhishek; Park, Sun Hong; Sohn, Yong Ho

doi:10.1007/s11669-019-00710-6

Cited by 12 publications

(6 citation statements)

References 12 publications

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“…The line analysis clearly shows how, starting from the SiO2 fiber and moving horizontally from left to right, one can find only Cu, for about the first 30 microns, until the appearance of what has been identified as the KV area (about 5–10 microns wide); then there is a Cu–Ni alloy interdiffusion zone (about 35 microns wide) with a high concentration of Cu, excluding a few microns near the only-Ni zone, that is, at the right side of the image. Figure 6 also shows that KVs are located in the Cu layer, as already demonstrated in [22,23].…”

Section: Methodssupporting

confidence: 77%

“…In this temperature range, the spectrum changes because of a nonlinear stress state, probably due to the formation of the KVs. The presence of voids is undesirable in most load bearing and thermal stressed applications and would significantly undermine the integrity of coatings, as demonstrated in [22]. Figure 5, showing a micrograph of a cross-section view of the sample after the 400 ∘C recovery, confirms that the diffusion phenomena are not present or at least irrelevant before this temperature, becoming significant above 700 ∘C, as shown in the graphs in Figure 8, Figure 9 and Figure 10.…”

Section: Resultsmentioning

confidence: 55%

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Critical Issues of Double-Metal Layer Coating on FBG for Applications at High Temperatures

Lupi

Felli

Dell’Era

et al. 2019

Sensors

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Use of fiber Bragg gratings (FBGs) to monitor high temperature (HT) applications is of great interest to the research community. Standard commercial FBGs can operate up to 600 ∘ C. For applications beyond that value, specific processing of the FBGs must be adopted to allow the grating not to deteriorate. The most common technique used to process FBGs for HT applications is the regeneration procedure (RP), which typically extends their use up to 1000 ∘ C. RP involves a long-term annealing of the FBGs, to be done at a temperature ranging from 550 to 950 ∘ C. As at that temperature, the original coating of the FBGs would burn out, they shall stay uncoated, and their brittleness is a serious concern to deal with. Depositing a metal coating on the FBGs prior to process them for RP offers an effective solution to provide them with the necessary mechanical strengthening. In this paper, a procedure to provide the FBG with a bimetallic coating made by copper and nickel electrodeposition (ED) is proposed, discussing issues related to the coating morphology, adherence to the fiber, and effects on the grating spectral response. To define the processing parameters of the proposed procedure, production tests were performed on dummy samples which were used for destructive SEM–EDS analysis. As a critical step, the proposed procedure was shown to necessitate a heat treatment after the nickel ED, to remove the absorbed hydrogen. The spectral response of the FBG samples was monitored along the various steps of the proposed procedure and, as a final proof test for adherence stability of the bimetallic coating, along a heating/cooling cycle from room temperature to 1010 ∘ C. The results suggest that, given the emergence of Kirkendall voids at the copper–nickel interface, occurring at the highest temperatures (700–1010 ∘ C), the bimetallic layer could be employed as FBG coating up to 700 ∘ C.

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Section: Methodssupporting

confidence: 77%

Section: Resultsmentioning

confidence: 55%

Critical Issues of Double-Metal Layer Coating on FBG for Applications at High Temperatures

Lupi

Felli

Dell’Era

et al. 2019

Sensors

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“…The evacuation and flushing procedure was repeated several times before the quartz tube was sealed, creating a closed, high purity Ar atmosphere for the diffusion couples. More details on diffusion couple fabrication can be found elsewhere. − Each diffusion couple was isothermally annealed at 900, 1000, 1100, and 1200 °C for 240, 120, 48, and 24 h, respectively. After annealing, all diffusion couples were water quenched to preserve the high temperature microstructure.…”

Section: Methodsmentioning

confidence: 99%

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

Mehta

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.

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“…For measurement of interdiffusion coefficients, metallographically polished surfaces ( ∼ 1μm surface finish) of two alloys were placed in intimate contact in two stainless steel jigs and held tightly by clamping screws. Details on diffusion couple fabrication for the determination of interdiffusion coefficients have been described elsewhere [28][29][30][31][32][33]. For measurement of tracer diffusion coefficients, an alloy disc polished on both sides was sandwiched between two alloys of the same composition.…”

Section: Introductionmentioning

confidence: 99%

Investigation of sluggish diffusion in FCC Al_0.25CoCrFeNi high-entropy alloy

Mehta

Sohn

2021

Materials Research Letters

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To validate the 'sluggish diffusion' in high-entropy alloys, interdiffusion coefficients of individual elements and tracer diffusion coefficient of Ni were experimentally determined in FCC Al 0.25 CoCrFeNi alloy. The tracer diffusion coefficient was determined without the application of radio-tracers using a novel analytical method proposed by Belova et al. based on linear response theory coupled with Boltzmann-Matano approach and Gaussian distribution function. Sluggish diffusion kinetics was not observed in alloys with higher configuration entropy in comparison to alloys with lower configuration entropy. Correspondingly, potential energy fluctuations in alloys with higher configuration entropy may not always result in anomalously slow diffusion kinetics. IMPACT STATEMENTDiffusion is determined not to be necessarily sluggish in Al 0.25 CoCrFeNi high-entropy alloy by experimental measurement of chemical and tracer diffusion coefficients.

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Effects of Marker Size and Distribution on the Development of Kirkendall Voids, and Coefficients of Interdiffusion and Intrinsic Diffusion

Cited by 12 publications

References 12 publications

Critical Issues of Double-Metal Layer Coating on FBG for Applications at High Temperatures

Critical Issues of Double-Metal Layer Coating on FBG for Applications at High Temperatures

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

Investigation of sluggish diffusion in FCC Al_0.25CoCrFeNi high-entropy alloy

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Effects of Marker Size and Distribution on the Development of Kirkendall Voids, and Coefficients of Interdiffusion and Intrinsic Diffusion

Cited by 12 publications

References 12 publications

Critical Issues of Double-Metal Layer Coating on FBG for Applications at High Temperatures

Critical Issues of Double-Metal Layer Coating on FBG for Applications at High Temperatures

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

Investigation of sluggish diffusion in FCC Al0.25CoCrFeNi high-entropy alloy

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Investigation of sluggish diffusion in FCC Al_0.25CoCrFeNi high-entropy alloy