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Type Seidman, David N.
  Publication Three-Dimensional Atom-Probe Tomography: Advances and Applications Volume Journal Article
Pages 2007
  Abstract Annual Review of Materials Research  
  Corporate Author  
Publisher 37  
Editor
  Summary Language 127-158 Series Editor field-ion microscopy, time-of-flight mass spectrometry, laser-assisted LEAPTM tomography, α-Al/Al3Sc heterophase interfaces, Ni-Al-Cr alloys, Ni-Al-Cr-Re alloys, InAs nanowires  
Abbreviated Series Title This review presents the historical temporal evolution of an atomprobe tomograph (APT) from its genesis (1973) from field-ion microscope images of individual tungsten atoms (1955). The capabilities of modern APTs employing either electrical or laser pulsing are discussed. The results of the application of APTs to specific materials science problems are presented for research performed at Northwestern University on the following problems: (a) the segregation of Mg at α-Al/Al3Sc heterophase interfaces, (b) phase decomposition in ternary Ni-Al-Cr and quaternary Ni-Al-Cr-Re alloys, and (c) 3-D nanoscale composition mapping of an InAs semiconductor nanowire whose growth was catalyzed by gold. These results demonstrate that it is now possible to obtain highly quantitative information from APT that can be compared with modeling, theory, simulations, and/or first-principles calculations.
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no NU @ karnesky @ 1926
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Marquis, E. A.; Seidman, D. N.; Asta, M.; Woodward, C.; Ozolins, V. Mg Segregation at Al/Al[sub:3]Sc Heterophase Interfaces on an Atomic Scale: Experiments and Computations Journal Article 2003 Physical Review Letters 91 3 036101: 1-4 Al-Sc alloys total-energy calculations wave basis-set molecular-dynamics transition aluminum precipitation diffusion scandium metals Microscopic factors governing solute partitioning in ternary two-phase Al-Sc-Mg alloys are investigated combining three-dimensional-atom-probe (3DAP) miscroscopy measurements with first-principles computations. 3DAP is employed to measure composition profiles with subnanometer-scale resolution, leading to the identification of a large enhancement of Mg solute at the coherent alpha -Al/Al3Sc (fcc/L12) heterophase interface. First-principles calculations establish an equilibrium driving force for this interfacial segregation reflecting the nature of the interatomic interactions. Marquis, E. A. Sandia Natl Labs, Livermore, CA 94551 USA USAF, Res Lab, Mat & Mfg Directorate, Wright Patterson AFB, OH 45433 USA Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA Univ Calif Los Angeles, Dept Mat Sci & Engn, Los Angeles, CA 90095 USA no NU @ karnesky @ 40
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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.; Riesterer, J. L.; Seidman, D. N.; Larson, D. J. Mg Segregation at Coherent and Semi-Coherent Al/Al[sub:3]Sc Interfaces Journal Article 2006 Microscopy and Microanalysis Microsc. Microanal. 12 S2 914-915 LEAP; Al-Sc Aluminum alloys containing Sc are promising materials for high-temperature structural applications due to the high strengthening effect of the Al3Sc (L12 structure) precipitates [1]. Further improvements in strength and nanostructural stability of Al-Sc based alloys are achieved by adding alloying elements, such as Mg, as solid-solution strengtheners. It is important to understand the effects of Mg in order to control not only the specific contribution of Mg to the properties of Al-Sc alloys (strengthening effect and creep resistance) but also the changes in the nanostructure. From previous work, it is known that Mg tends to segregate to the coherent Al/Al3Sc interface due to positive interactions between Mg and Sc atoms [2]. This paper reports measurements of Mg segregation at the Al/Al3Sc interface and compares the segregation level between coherent and semicoherent Al/Al3Sc interfaces. A cast Al-2 wt.% Mg-0.2 wt.% Sc alloy was annealed at 618C in air for 24 hours, quenched into cold water, and then aged in air at 300C for 24 hours. One sample was subsequently aged at 400oC for 240 hours. Three-dimensional atom probe (3DAP) microscopy tips were obtained by a double electro-polishing technique. Field evaporation was performed at 30 K with a pulse fraction of 20 % at a frequency of 200 kHz using a LEAP microscope. Transmission electron microscopy (TEM) imaging was performed on a JEOL 1200 microscope. During aging at 300oC, Al3Sc precipitates are formed with a high number density (~2 1022 precipitates/m3), which is advantageous for random 3DAP microscope observations. The average radius of the precipitates is 2 nm and the interface is coherent (Fig. 1). After aging at 400oC, however, the average radius of the precipitates is ~19 nm and dislocations loops are observed at the matrix/precipitate interface. The number density of precipitates has also decreased dramatically (~1019 precipitates/m3) and is no longer sufficient for random atom probe observations. Atom probe tips were therefore observed by TEM to confirm the semi-coherent nature of the Al/Al3Sc interface and to determine the position of the precipitates with respect to the tip apex. Micro-polishing was used to position precipitates to within ~100 nm of the apex. A TEM image of a tip is shown in FIG.2. Al3Sc precipitates are visible with dislocations at the matrix/precipitate interfaces. Coherency loss may occur when the precipitate diameter is larger than the spacing between the misfit dislocations. This spacing is of the order of α/ε, where ε = 0.62% is the lattice parameter misfit between the α-Al matrix containing 2.2 at.% Mg and the Al3Sc phase [3,4], and α = 0.20 nm is the spacing between {200} planes. The calculated equilibrium dislocation spacing is therefore 32 nm, in good agreement with the presence of interfacial dislocations for precipitates with diameter of ~38 nm. Comparison is made between the segregation levels measured for coherent and semicoherent interfaces. The role of the interfacial dislocations will be discussed. References [1] Toporova L.S., Eskin D.G., Kharakterova M.L., Dobatkina T.B. Advanced aluminum alloys containing scandium. Amsterdam: Gordon & Breach; 1998. [2] Marquis E.A., Seidman D.N., Asta M., Woodward C., Ozolins V., Phys. Rev. Letters 91 (2003) 036101 1-3 [3] Hatch J.E. Aluminum: properties and physical metallurgy. Metals Park (OH): ASM; 1984. no NU @ karnesky @ 753
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Fuller, Christian B.; Seidman, David N.; Dunand, David C. Creep Properties of Coarse-Grained Al(Sc) Alloys at 300°C Journal Article 1999 Scripta Materialia Scripta Mater. 40 6 691-696 Al-Sc no NU @ karnesky @ 527
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Harada, Y.; Dunand, D.C. Thermal Expansion of Al[sub:3]Sc and Al[sub:3](Sc[sub:0.75]X[sub:0.25]) Journal Article 2003 Scripta Materialia Scripta Mater. 48 3 219-222 intermetallic compound aluminum alloys thermal expansion scandium physical-properties al(sc) alloys The thermal expansion coefficient of Al3Sc and Al3(Sc0.75X0.25), where X is Ti, Y, Zr or Hf, was measured by dilatometry between 25 and 1000 °C. The measured value, (16±1)×10-6 K-1, is constant between 25 and 900 °C and insensitive to alloying element. Good agreement is found with a literature value determined from first-principle calculations Dunand, D. C. Northwestern Univ, Dept Mat Sci & Engn, 2220 Campus Dr, Evanston, IL 60208 USA Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA Natl Inst Adv Ind Sci & Technol, Inst Mech Syst Engn, Tsukuba, Ibaraki 3058564, Japan ....there is an error: we should have written : alloying the matrix with magnesium, which INCREASES the lattice constant of Al ... no NU @ karnesky @ 542
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Marquis, Emmanuelle A.; Dunand, David C. Model for Creep Threshold Stress in Precipitation-Strengthened Alloys with Coherent Particles Journal Article 2002 Scripta Materialia Scripta Mater. 47 8 503-508 creep threshold stress precipitation strengthening aluminum alloys dislocation mobility al(sc) alloys al3sc; Al-Sc The general climb model for creep threshold stress for dislocations interacting with incoherent particles is modified for the case of coherent precipitates, by taking into account elastic interactions between matrix dislocations and particles due to particle/matrix stiffness and lattice mismatches. The model is in qualitative agreement with experimental data for the Al–Sc system. Dunand, D. C. Northwestern Univ, Dept Mat Sci & Engn, MLSB 1123,2225 N Campus Dr, Evanston, IL 60208 USA Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA no NU @ karnesky @ 569
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Fuller, Christian B.; Seidman, David N.; Dunand, David C. Mechanical Properties of Al(Sc,Zr) Alloys at Ambient and Elevated Temperatures Journal Article 2003 Acta Materialia Acta Mater. 51 16 4803-4814 al-sc-zr alloys mechanical properties creep deformation mechanisms strengthened alloys threshold stress creep-properties al3sc microstructure particles additions evolution model sc This study investigates the mechanical properties of ternary Al(Sc,Zr) alloys containing 0.27–0.77 vol.% of Al3(Sc,Zr) precipitates with an average radius left angle bracketrright-pointing angle bracket=2−24 nm. Microhardness values at ambient temperature follow predictions of the Orowan dislocation bypass mechanism, with a transition to the precipitate shearing mechanism predicted for left angle bracketrright-pointing angle bracket larger than 2 nm. Addition of Zr to binary Al(Sc) alloys delays the onset and kinetics of over-aging at 350 and 375 °C, but has little influence on the magnitude of the peak microhardness. Creep deformation at 300 °C is characterized by a threshold stress, which increases with left angle bracketrright-pointing angle bracket in the range 2–9 nm, in agreement with prior results for binary Al(Sc) alloys and a recently developed general climb model considering elastic interactions between dislocations and coherent, misfitting precipitates. At constant left angle bracketrright-pointing angle bracket and precipitate volume fraction, Zr additions do not significantly improve the creep resistance of Al(Sc) alloys. Dunand, D. C. Northwestern Univ, Dept Mat Sci & Engn, 2220 Campus Dr, Evanston, IL 60208 USA Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA no NU @ karnesky @ 224
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Marquis, Emmanuelle A.; Seidman, David N.; Dunand, David C. Effect of Mg Addition on the Creep and Yield Behavior of an Al–Sc Alloy Journal Article 2003 Acta Materialia Acta Mater. 51 16 4751-4760 Transmission electron microscopy; Aluminum alloys; Coarsening; Creep; Al3Sc precipitates; olid-solution alloys dislocation climb viscous glide deformation stress dependence particles fracture; Al-Sc The relationships between microstructure and strength were studied at room temperature and 300 °C in an Al–2 wt% Mg–0.2 wt% Sc alloy, containing Mg in solid-solution and Al3Sc (L12 structure) as nanosize precipitates. At room temperature, the yield strength is controlled by the superposition of solid-solution and precipitation strengthening. At 300 °C and at large applied stresses, the creep strength, which is characterized by a stress exponent of ~5, is significantly improved compared to binary Al–Sc alloys, and is independent of the size of the Al3Sc precipitates. At small applied stress, a threshold stress exists, increasing from 9% to 70% of the Orowan stress with increasing Al3Sc precipitate radius from 2 to 25 nm. An existing model based on a climb-controlled bypass mechanism is in semi-quantitative agreement with the precipitate radius dependence of the threshold stress. The model is, however, only valid for coherent precipitates, and the Al3Sc precipitates lose coherency for radii larger than 11 nm. For semi-coherent precipitates with radii greater than 15 nm, the threshold stress remains high, most likely because of the presence of interfacial misfit dislocations. Marquis, E. A. Sandia Natl Labs, Thin Film & Interface Dept, Livermore, CA 94550 USA Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA no NU @ karnesky @ 212
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Marquis, Emmanuelle A.; Seidman, David N.; Dunand, David C. Precipitation Strengthening at Ambient and Elevated temperatures of Heat-Treatable Al(Sc) Alloys [Acta Materialia 50(16), pp. 4021–4035] Journal Article 2003 Acta Materialia Acta Mater. 51 1 285-287 Al-Sc In the final printed issue, the Publisher regrets to inform that the sequence of authors’ names given under the title on page 4021 was incorrect. The correct sequence is now shown above. The Publisher also wishes to apologise for the poor quality reproduction of Fig. 1, Fig. 9 and Fig. 10, which are now reprinted correctly below: no NU @ karnesky @ 213
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