scholarly journals A Reassessment of the Metastable Miscibility Gap in Al-Ag Alloys by Atom Probe Tomography

2007 ◽  
Vol 13 (6) ◽  
pp. 484-492 ◽  
Author(s):  
Emmanuelle A. Marquis
Keyword(s):  
Atom Probe Tomography ◽  
Temporal Evolution ◽  
Atom Probe ◽  
Time Dependent ◽  
Miscibility Gap ◽  
Preliminary Results

The evolution of Guinier-Preston zones in an Al-2.7 at.% Ag alloy was studied using atom probe tomography. The composition and morphology of the GP zones are time dependent, explaining discrepancies in previous work. This result requires the metastable miscibility gap for GP zones to be reevaluated, highlighting the importance of the temporal evolution of the GP zones. Preliminary results on the composition of γ′ and γ plates are also presented.

Revisiting Temporal Evolution of Cu-Rich Precipitates in Fe–Cu Alloy: Correlative Small Angle Neutron Scattering and Atom-Probe Tomography Studies

2019 ◽  
Vol 25 (4) ◽  
pp. 840-848 ◽  
Author(s):  
Sarita Ahlawat ◽  
Sudip Kumar Sarkar ◽  
Debasis Sen ◽  
Aniruddha Biswas
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Atom Probe Tomography ◽  
Small Angle Neutron Scattering ◽  
Nuclear Reactor ◽  
Temporal Evolution ◽  
Morphological Evolution ◽  
Atom Probe ◽  
Pressure Vessels ◽  
Morphological Transformation

AbstractBinary Fe–Cu alloys are effective prototypes for investigating radiation-induced formation and growth of nanometric Cu-rich precipitates (CRPs) in nuclear reactor pressure vessels. In this report, the temporal evolution of CRPs during thermal aging of Fe–Cu binary alloys has been investigated by using complementary techniques such as atom probe tomography (APT) and small-angle neutron scattering (SANS). We report a detailed quantitative evolution of a rarely observed morphological transformation of Cu precipitates from spherical to ellipsoid with a significant change (approximately two times) in aspect ratio, an effect known to be associated with the 9R-3R structural transition of the precipitates. It is demonstrated through APT that the precipitates remain spherical up to 8 h, however, they subsequently convert to oblate ellipsoid upon further aging. SANS analysis also detected signs of this morphological transition in reciprocal space. Furthermore, SANS quantifies evolution of the precipitates and corroborates well with the APT results. Interestingly, the power-law exponent of the temporal evolution for mean size and number density agree reasonably well with the Lifshitz–Slyozov–Wagner model, in spite of the complex morphological evolution of the precipitates.

scholarly journals Precision Thermal Treatments, Atom Probe Characterization, and Modeling to Describe the Fe-Cr Metastable Miscibility Gap

2021 ◽  
Vol 52 (4) ◽  
pp. 1453-1464
Author(s):  
Alexander Dahlström ◽  
Frederic Danoix ◽  
Peter Hedström ◽  
Joakim Odqvist ◽  
Malin Selleby ◽  
...  
Keyword(s):  
High Precision ◽  
Thermodynamic Modeling ◽  
Experimental Work ◽  
Atom Probe Tomography ◽  
Atom Probe ◽  
Miscibility Gap ◽  
Thermal Treatments ◽  
Micro Hardness ◽  
Consolute Temperature ◽  
Vickers Micro Hardness

Abstract The Fe-Cr metastable miscibility gap has been studied by high-precision thermal treatments, Vickers micro-hardness (HV) measurements, and atom probe tomography (APT). Thermodynamic modeling further supplements the experimental work. The results obtained show that recent thermodynamic descriptions of the metastable miscibility gap found in literature generally overestimates the consolute temperature. We can show that the source of ambiguity in previous studies is most likely a lack of clear distinction between Cr-Cr clustering and $$ \alpha^{\prime} $$ α ′ formation. This distinction is here made by APT results, and it leads to a determined consolute temperature of 580 ± 1 °C for Fe0.50Cr0.50. The revised thermodynamic modeling of the metastable miscibility gap captures the experimental results and is consistent with the overall picture from the Fe-Cr data in the literature. Graphic Abstract

The β'-α' Interaction: a Study of early Stages of Phase Separation in a Fe-20%Cr-6%Al-0.5%Ti Alloy

2011 ◽  
Vol 172-174 ◽  
pp. 315-320
Author(s):  
Carlos Capdevila ◽  
Michael K. Miller ◽  
K.F. Russell ◽  
J. Chao ◽  
F.A. López
Keyword(s):  
Phase Separation ◽  
Atom Probe Tomography ◽  
Temporal Evolution ◽  
Theoretical Calculations ◽  
Three Dimensional ◽  
Atom Probe ◽  
Early Stages ◽  
Β Phase ◽  
Α Phase ◽  
Power Measurements

The temporal evolution of the microstructure resulting from phase separation into Fe-rich (α), Cr-rich (α¢), and Fe(Ti,Al) (β¢) phases of a Fe-20Cr-6Al-0.5Ti alloy has been analyzed by thermoelectric power measurements (TEP). The early stages of decomposition and the evolution of the three-dimensional microstructure have been analyzed by atom probe tomography (APT). The roles of Cr, Al, and Ti during the decomposition process have been investigated in terms of solute partitioning between the phases. Analysis of proximity histograms revealed that significant Al and Ti partitioning occurs, which is consistent with theoretical calculations. The results indicate that as the α-α¢ phase separation proceeds, Al and Ti are rejected into the α phase, which causes the β¢ phase to nucleate on the surface of the α¢ phase.

scholarly journals Probing the Miscibility Gap of the Pt–Pd Binary System by Atom Probe Tomography

2021 ◽  
pp. 1-11
Author(s):  
Yoonhee Lee ◽  
Patrick Stender ◽  
Sebastian Manuel Eich ◽  
Guido Schmitz
Keyword(s):  
Diffusion Coefficients ◽  
Atom Probe Tomography ◽  
Series Solution ◽  
Isothermal Annealing ◽  
Ion Beam ◽  
Atom Probe ◽  
Miscibility Gap ◽  
Ion Beam Sputtering ◽  
Diffusion Controlled ◽  
Beam Sputtering

To solve the uncertainty of the platinum (Pt)–palladium (Pd) phase diagram, especially the existence of a suggested miscibility gap, atom probe tomography (APT) was used to determine the time evolution of the composition after heat treatment. Due to the extraordinarily slow diffusion in the temperature range of the controversial phase separation, the investigated volume was limited to nano-sized multiple layers deposited by ion beam sputtering (IBS). The evaporated volume was reconstructed from the obtained datasets and the respective diffusion coefficients were determined using the Fourier series solution of the diffusion equation. Beginning with pure Pt and Pd layers annealed at 673, 773, 873, and 973 K, the mixing appears to be purely diffusion controlled in the chosen annealing times, but the state of complete mixing was still not observed. Therefore, extended isothermal annealing sequences at 673 and 773 K with pre-alloyed layers have been carried out. They clearly suggest complete mixing even at the lowest investigated temperatures.

A Comparison of Tem and Apfim to the Interpretation of Modulated Microstructures

1985 ◽  
Vol 43 ◽  
pp. 70-71
Author(s):  
M.G. Burke ◽  
M.K. Miller
Keyword(s):  
Low Temperature ◽  
Microstructural Characterization ◽  
Superlattice Reflection ◽  
High Volume ◽  
Atom Probe ◽  
Dark Field ◽  
Miscibility Gap ◽  
Second Phase ◽  
Two Phase ◽  
Probe Field

Interpretation of fine-scale microstructures containing high volume fractions of second phase is complex. In particular, microstructures developed through decomposition within low temperature miscibility gaps may be extremely fine. This paper compares the morphological interpretations of such complex microstructures by the high-resolution techniques of TEM and atom probe field-ion microscopy (APFIM).The Fe-25 at% Be alloy selected for this study was aged within the low temperature miscibility gap to form a <100> aligned two-phase microstructure. This triaxially modulated microstructure is composed of an Fe-rich ferrite phase and a B2-ordered Be-enriched phase. The microstructural characterization through conventional bright-field TEM is inadequate because of the many contributions to image contrast. The ordering reaction which accompanies spinodal decomposition in this alloy permits simplification of the image by the use of the centered dark field technique to image just one phase. A CDF image formed with a B2 superlattice reflection is shown in fig. 1. In this CDF micrograph, the the B2-ordered Be-enriched phase appears as bright regions in the darkly-imaging ferrite. By examining the specimen in a [001] orientation, the <100> nature of the modulations is evident.

scholarly journals Correlating nanoscale secondary ion mass spectrometry and atom probe tomography analysis of uranium enrichment in metallic nuclear fuel

The Analyst ◽  
2021 ◽  
Vol 146 (1) ◽  
pp. 69-74
Author(s):  
Elizabeth Kautz ◽  
John Cliff ◽  
Timothy Lach ◽  
Dallas Reilly ◽  
Arun Devaraj
Keyword(s):  
Mass Spectrometry ◽  
Nuclear Fuel ◽  
Atom Probe Tomography ◽  
Secondary Ion Mass Spectrometry ◽  
Atom Probe ◽  
Uranium Enrichment ◽  
Length Scales ◽  
Atom Probe Tomography Analysis ◽  
Secondary Ion ◽  
Tomography Analysis

235U enrichment in a metallic nuclear fuel was measured via NanoSIMS and APT, allowing for a direct comparison of enrichment across length scales and resolutions.

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