Experimental evaluation of particle coarsening theories

Jayanth, C. S.; Nash, Philip

doi:10.1179/026708390790190874

Cited by 9 publications

(11 citation statements)

References 12 publications

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“…Although rare, the coalescence among coherent c 0 -precipitates during precipitation in the absence of an external stress field has been reported in Ni-Al-Cr [41,42], Ni-AlMo [43], and Ni-Al-Co [44] alloys during the intermediate to late stages of coarsening for aging temperatures ranging from 750 to 850°C and / eq > 35%. In the Ni-Al-Cr alloy studied, coagulation and coalescence between nanometersized precipitates occurs in the early stages of decomposition at small /(t), for instance /(t = 4 h) = 5.2%, whereas after 4 h (the peak value of N v ) coagulation no longer occurs and the fraction, f, of coalesced c 0 -precipitates decays with increasing aging time (Fig.…”

Section: Discussionmentioning

confidence: 99%

Temporal evolution of the nanostructure and phase compositions in a model Ni–Al–Cr alloy

et al. 2006

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In a Ni-5.2 Al-14.2 Cr at.% alloy with moderate solute supersaturations and a very small c/c 0 lattice parameter misfit, the nanostructural and compositional pathways during c 0 (L1 2 ) precipitation at 873 K are investigated using atom-probe tomography, conventional transmission electron microscopy, and hardness measurements. Nucleation of high number densities (N v > 10 23 m À3 ) of solute-rich precipitates (mean radius = AERae = 0.75 nm), with a critical nucleus composition of Ni-18.3 ± 0.9 Al-9.3 ± 0.7 Cr at.%, initiates between 0.0833 and 0.167 h. With increasing aging time (a) the solute concentrations decay in spheroidal precipitates (AERae < 10 nm); (b) the observed early-stage coalescence peaks at maximum N v in coincidence with the smallest interprecipitate spacing; and (c) the reaction enters a quasi-stationary regime where growth and coarsening operate concomitantly. During this quasi-stationary regime, the c (face-centered cubic)-matrix solute supersaturations decay with a power-law dependence of about À1/3, while the dependencies of AERae and N v are 0.29 ± 0.05 and À0.64 ± 0.06 at a coarsening rate slower than model predications. Coarsening models allow both equilibrium phase compositions to be determined from the compositional measurements. The observed early-stage coalescence is discussed in further detail.

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Section: Discussionmentioning

confidence: 99%

Temporal evolution of the nanostructure and phase compositions in a model Ni–Al–Cr alloy

et al. 2006

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“…The data of Ardell and Nicholson [10] are shown in a. The data of Jayanth and Nash [50] (cross) and Irisarri et al [51] (circle) are shown in b. The solid curves show the PSD of the TIDC theory for n = 2.424 and the dashed curves show the PSD of the LSW theory the smaller number of particles counted at larger particle sizes, increases the uncertainties in the PSDs and results in more uncertain values of n. As was the case for the Ni-Ti alloys re-examined previously [49], there were Ni-Ga PSDs that could not be fitted (2 for the data of Kim and Ardell [15], 3 for the data of Wimmel and Ardell [16]) and one Ni-Ge PSD that could not be fitted [18].…”

Section: Examination Of the Data On Binary Ni Alloysmentioning

confidence: 99%

“…The main significant procedural difference between this and previous work is that populations of data (aging times at a specific temperature) were evaluated individually, yielding average values of n with their variances, which were then used to calculate the average values for all populations. For example, the PSDs of c 0 precipitates in Ni-Al alloys reported by Ardell and Nicholson [10] for their three aging conditions, and those reported by Jayanth and Nash [50] and Irisarri et al [51], were all evaluated as individual populations, each of which produced an average value of n with its own variance. Previously, the values of n obtained by fitting the individual PSDs were averaged irrespective of source and aging conditions.…”

Section: Examination Of the Data On Binary Ni Alloysmentioning

confidence: 99%

“…The collective PSDs of Ardell and Nicholson [10] are shown in Fig. 1a and the PSDs of Jayanth and Nash [50] and Irisarri et al [51] are shown in Fig. 1b.…”

Section: Examination Of the Data On Binary Ni Alloysmentioning

confidence: 99%

“…This is not so obvious for the other alloys for a variety of different reasons. One is that the counting statistics were much better for Ni-Al: Ardell and Nicholson [10] measured more than 400 particles, Jayanth and Nash [50] measured over 1000 particles and Irisarri et al [51] measured 350 particles on average. For many of the other sets of data fewer than 300 particles were counted, so the spread in the values of g(u) at any given value of u is far larger for the other alloys than for Ni-Al.…”

Section: Examination Of the Data On Binary Ni Alloysmentioning

confidence: 99%

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A1-L12 interfacial free energies from data on coarsening in five binary Ni alloys, informed by thermodynamic phase diagram assessments

Ardell

2011

J Mater Sci

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The data on coarsening of c 0 -type precipitates (Ni 3 X, with the L1 2 crystal structure) in Ni-Al, Ni-Ga, Ni-Ge, Ni-Si, and Ni-Ti alloys are re-evaluated in the context of recent (TIDC) and classical (LSW) theories of coarsening, with the objective of ascertaining the best values possible of interfacial free energies, r, of the c/c 0 interfaces in these five alloy systems. The re-evaluations include fitting of the particle size distributions, reanalyzing all the available data on the kinetics of particle growth and kinetics of solute depletion, and using thermodynamic assessments of the binary alloy phase diagrams to calculate curvatures of the Gibbs free energies of mixing. The product of the work is two sets of interfacial free energies, one set for the analysis using the recent TIDC theory and the other for the analysis using the classical LSW theory. The TIDC-based analysis yields lower values of r by about a factor of 2/3. All the interfacial energies are considerably larger, by factors ranging from *4 to 10, than those previously reported, which were for the most part calculated from data on coarsening assuming idealsolution thermodynamics. In the TIDC theory the width of the interface, d, is allowed to increase with particle size, r. A simple equation relating r to the ratio of the gradient energy and d is used to show that r can remain constant even though d increases with r. Published work supporting this contention is presented and discussed.

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Structural Stability of Platinum-Group-Metal-Modified γ + γ′ Ni-Base Alloys

Heidloff

Sluytman

Pollock

et al. 2009

Metall Mater Trans A

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The structural and surface stabilities of two experimental c-Ni+c¢-Ni 3 Al-base alloys containing Pt or Ir were investigated. These alloys are representative of alloys currently being developed to occupy a unique domain with a good combination of high-temperature strength and resistance to oxidation and hot corrosion. Structural characterization included differential thermal analysis (DTA), transmission synchrotron X-ray analysis, precipitate morphology evolution, phase-partitioning behavior, transmission electron microscopy (TEM), dislocation analysis, and isothermal precipitate-coarsening behavior. Electron microprobe investigations showed that Pt partitions largely to the c¢ phase, while Ir partitions more to the c phase. As a consequence, the influence of these two elements on the c-c¢ lattice-parameter mismatch was quite different. Specifically, synchrotron X-ray analysis confirmed a positive c-c¢ misfit in both the Pt-and Ir-modified alloys in the temperature range 700°C to 1200°C; however, the Pt partitioning to the c¢ phase resulted in a much larger misfit. The coarsening kinetics of both alloys followed a cubic time dependence and Pt addition was more effective than Ir in slowing the coarsening rate. Thermodynamic predictions about elemental partitioning and about the solidus, liquidus, and c¢ solvus temperatures were made using the software package PANDAT; the results of these predictions were compared with experimental measurements.

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Experimental evaluation of particle coarsening theories

Cited by 9 publications

References 12 publications

Temporal evolution of the nanostructure and phase compositions in a model Ni–Al–Cr alloy

Temporal evolution of the nanostructure and phase compositions in a model Ni–Al–Cr alloy

A1-L12 interfacial free energies from data on coarsening in five binary Ni alloys, informed by thermodynamic phase diagram assessments

Structural Stability of Platinum-Group-Metal-Modified γ + γ′ Ni-Base Alloys

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