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Title Blavette, D.; Cadel, E.; Pareige, C.; Deconihout, B.; Caron, P.
Year Phase Transformation and Segregation to Lattice Defects in Ni-Base Superalloys
Abbreviated Journal Journal Article
Issue 2007 Keywords Microscopy and Microanalysis
Thesis 13
Place of Publication 06 Language 464-483
Original Title atom probe, nickel, superalloy, precipitation
Series Title Nanostructural features of nickel-base superalloys as revealed by atom probe field ion microscopy (APFIM) and atom probe tomography (APT) are reviewed. The more salient information provided by these techniques is discussed through an almost exhaustive analysis of literature over the last 30 years. Atom probe techniques are shown to be able to measure the composition of tiny [gamma]′ precipitates, a few nanometers in size, and to reveal chemical order within these precipitates. Phase separation kinetics in model NiCrAl alloys was investigated with both 3DAP and Monte-Carlo simulation. Results are shown to be in good agreement. Plane by plane analysis of {001} planes of Ni3Al-type [gamma]′ phase makes it possible to estimate the degree of order as well as the preferential sites of various addition elements (Ti, Cr, Co, W, Ta, Re, Ru, etc.) included in superalloys. Clustering effects of Re in the [gamma] solid solution were also exhibited. Due to its ultrahigh depth resolution, the microchemistry of interfaces and grain boundaries can be characterized on an atomic scale. Grain boundaries in Astroloy or N18 superalloys were found to be enriched in B, Mo, and Cr and Al depleted. Series Volume
Serial Orig Record
no NU @ karnesky @ 10098
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Bunton, J.H.; Olson, J.D.; Lenz, D.R.; Kelly, T.F. Advances in Pulsed-Laser Atom Probe: Instrument and Specimen Design for Optimum Performance Journal Article 2007 Microscopy and Microanalysis 13 06 418-427 pulsed-laser atom probe, PLAP, laser, instrument, specimen, sample preparation, LEAP microscopy The performance of the pulsed-laser atom probe can be limited by both instrument and specimen factors. The experiments described in this article were designed to identify these factors so as to provide direction for further instrument and specimen development. Good agreement between voltage-pulsed and laser-pulsed data is found when the effective pulse fraction is less than 0.2 for pulsed-laser mode. Under the conditions reported in this article, the thermal tails of the peaks in the mass spectra did not show any significant change when produced with either a 10-ps or a 120-fs pulsed-laser source. Mass resolving power generally improves as the laser spot size and laser wavelength are decreased and as the specimen tip radius, specimen taper angle, and thermal diffusivity of the specimen material are increased. However, it is shown that two of the materials used in this study, aluminum and stainless steel, depend on these factors differently. A one-dimensional heat flow model is explored to explain these differences. The model correctly predicts the behavior of the aluminum samples, but breaks down for the stainless steel samples when the tip radius is large. A more accurate three-dimensional model is needed to overcome these discrepancies. no NU @ karnesky @ 10100
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Cerezo, A.; Clifton, P.H.; Lozano-Perez, S.; Panayi, P.; Sha, G.; Smith, G.D.W. Overview: Recent Progress in Three-Dimensional Atom Probe Instruments and Applications Journal Article 2007 Microscopy and Microanalysis 13 06 408-417 atom probe, tomography, semiconductors, laser pulsing, specimen preparation, grain boundary, steels Over the last few years there have been significant developments in the field of three-dimensional atom probe (3DAP) analysis. This article reviews some of the technical compromises that have led to different instrument designs and the recent improvements in performance. An instrument has now been developed, based around a novel reflectron configuration combining both energy compensation and focusing elements, that yields a large field of view and very high mass resolution. The use of laser pulsing in the 3DAP, together with developments in specimen preparation methods using a focused ion-beam instrument, have led to a significant widening in the range of materials science problems that can be addressed with the 3DAP. Recent studies of semiconductor materials and devices are described. no NU @ karnesky @ 10107
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Geiser, B.P.; Kelly, T.F.; Larson, D.J.; Schneir, J.; Roberts, J.P. Spatial Distribution Maps for Atom Probe Tomography Journal Article 2007 Microscopy and Microanalysis 13 06 437-447 atom probe tomography (APT), spatial distribution maps (SDM), Fourier analysis, spatial resolution, trajectory aberration, crystal structure A real-space technique for finding structural information in atom probe tomographs, spatial distribution maps (SDM), is described. The mechanics of the technique are explained, and it is then applied to some test cases. Many applications of SDM in atom probe tomography are illustrated with examples including finding crystal lattices, correcting lattice strains in reconstructed images, quantifying trajectory aberrations, quantifying spatial resolution, quantifying chemical ordering, dark-field imaging, determining orientation relationships, extracting radial distribution functions, and measuring ion detection efficiency. no NU @ karnesky @ 10106
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Gorman, B.P.; Norman, A.G.; Yan, Y. Atom Probe Analysis of III–V and Si-Based Semiconductor Photovoltaic Structures Journal Article 2007 Microscopy and Microanalysis 13 06 493-502 semiconductor, solar cell, TEM, atom probe, doping interfaces The applicability of atom probe to the characterization of photovoltaic devices is presented with special emphasis on high efficiency III–V and low cost ITO/a-Si:H heterojunction cells. Laser pulsed atom probe is shown to enable subnanometer chemical and structural depth profiling of interfaces in III–V heterojunction cells. Hydrogen, oxygen, and phosphorus chemical profiling in 5-nm-thick a-Si heterojunction cells is also illustrated, along with compositional analysis of the ITO/a-Si interface. Detection limits of atom probe tomography useful to semiconductor devices are also discussed. Gaining information about interfacial abruptness, roughness, and dopant profiles will allow for the determination of semiconductor conductivity, junction depletion widths, and ultimately photocurrent collection efficiencies and fill factors. no NU @ karnesky @ 10103
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Knipling, K.E.; Dunand, D.C.; Seidman, D.N. Atom Probe Tomographic Studies of Precipitation in Al-0.1Zr-0.1Ti (at.%) Alloys Journal Article 2007 Microscopy and Microanalysis 13 06 503-516 atom probe tomography, Al[sub:3]Zr precipitates, local magnification, Al-Zr-Ti Atom probe tomography was utilized to measure directly the chemical compositions of Al3(Zr1−xTix) precipitates with a metastable L12 structure formed in Al-0.1Zr-0.1Ti (at.%) alloys upon aging at 375°C or 425°C. The alloys exhibit an inhomogeneous distribution of Al3(Zr1−xTix) precipitates, as a result of a nonuniform dendritic distribution of solute atoms after casting. At these aging temperatures, the Zr:Ti atomic ratio in the precipitates is about 10 and 5, respectively, indicating that Ti remains mainly in solid solution rather than partitioning to the Al3(Zr1−xTix) precipitates. This is interpreted as being due to the very small diffusivity of Ti in [alpha]-Al, consistent with prior studies on Al-Sc-Ti and Al-Sc-Zr alloys, where the slower diffusing Zr and Ti atoms make up a small fraction of the Al3(Sc1−xTix/Zrx) precipitates. Unlike those alloys, however, the present Al-Zr-Ti alloys exhibit no interfacial segregation of Ti at the matrix/precipitate heterophase interface, a result that may be affected by a significant disparity in the evaporation fields of the [alpha]-Al matrix and Al3(Zr1−xTix) precipitates and/or a lack of local thermodynamic equilibrium at the interface. no NU @ karnesky @ 10102
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Marquis, E.A. A Reassessment of the Metastable Miscibility Gap in Al-Ag Alloys by Atom Probe Tomography Journal Article 2007 Microscopy and Microanalysis 13 06 484-492 Guinier-Preston zones, atom probe tomography, Al, Ag, alloy 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 [gamma]′ and [gamma] plates are also presented. no NU @ karnesky @ 10101
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Miller, M.K.; Russell, K.F.; Thompson, K.; Alvis, R.; Larson, D.J. Review of Atom Probe FIB-Based Specimen Preparation Methods Journal Article 2007 Microscopy and Microanalysis 13 06 428-436 atom probe tomography, specimen preparation, focused ion beam Several FIB-based methods that have been developed to fabricate needle-shaped atom probe specimens from a variety of specimen geometries, and site-specific regions are reviewed. These methods have enabled electronic device structures to be characterized. The atom probe may be used to quantify the level and range of gallium implantation and has demonstrated that the use of low accelerating voltages during the final stages of milling can dramatically reduce the extent of gallium implantation. no NU @ karnesky @ 10099
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Ringer, S.P.; Larson, D.J.; Moody, M.P.; Miller, M.K.; Kelly, T.F. Introduction: Special Issue on Atom Probe Tomography Journal Article 2007 Microscopy and Microanalysis 13 06 407-407 In February 2006, in conjunction with the 19th Australian Conference on Microscopy and Microanalysis held in Sydney, the 2nd Australian Workshop on Atom Probe Tomography was convened by S.P. Ringer, M.K. Miller, D.A. Saxey, and R. Zheng at the Australian Key Centre for Microscopy and Microanalysis at The University of Sydney. The topics covered at that workshop included specimen preparation; data acquisition and data analysis methods for atom probe tomography; applications to spinodal alloys, phase transformations, light metals, atomic clustering, and detection methods, as well as future directions of the science and technology of atom probe tomography. The presentations and discussions that took place at this workshop, which was attended by more than 30 people, provided the inspiration for this special issue of Microscopy and Microanalysis. no NU @ karnesky @ 10105
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Stephenson, L.T.; Moody, M.P.; Liddicoat, P.V.; Ringer, S.P. New Techniques for the Analysis of Fine-Scaled Clustering Phenomena within Atom Probe Tomography (APT) Data Journal Article 2007 Microscopy and Microanalysis 13 06 448-463 atom probe tomography, solute clustering, cluster algorithms, nearest neighbors, data analysis, data mining Nanoscale atomic clusters in atom probe tomographic data are not universally defined but instead are characterized by the clustering algorithm used and the parameter values controlling the algorithmic process. A new core-linkage clustering algorithm is developed, combining fundamental elements of the conventional maximum separation method with density-based analyses. A key improvement to the algorithm is the independence of algorithmic parameters inherently unified in previous techniques, enabling a more accurate analysis to be applied across a wider range of material systems. Further, an objective procedure for the selection of parameters based on approximating the data with a model of complete spatial randomness is developed and applied. The use of higher nearest neighbor distributions is highlighted to give insight into the nature of the clustering phenomena present in a system and to generalize the clustering algorithms used to analyze it. Maximum separation, density-based scanning, and the core linkage algorithm, developed within this study, were separately applied to the investigation of fine solute clustering of solute atoms in an Al-1.9Zn-1.7Mg (at.%) at two distinct states of early phase decomposition and the results of these analyses were evaluated. no NU @ karnesky @ 10104
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