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Type Marquis, E. A.; Seidman, D. N.; Asta, M.; Woodward, C.; Ozolins, V.
  Publication Mg Segregation at Al/Al[sub:3]Sc Heterophase Interfaces on an Atomic Scale: Experiments and Computations Volume Journal Article
Pages 2003
  Abstract Physical Review Letters  
  Corporate Author (up)  
Publisher 91  
Editor 3
  Summary Language 036101: 1-4 Series Editor Al-Sc alloys total-energy calculations wave basis-set molecular-dynamics transition aluminum precipitation diffusion scandium metals  
Abbreviated Series Title 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.
  Series Issue 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 ISSN  
Medium
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no NU @ karnesky @ 40
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Chao, Paul; Karnesky, Richard A. Hydrogen Isotope trapping in Al-Cu binary alloys Journal Article 2016 Materials Science & Engineering A Mater Sci Eng A 658 422-428 Age-hardening, Aluminium alloys, Al-Cu, Hydrogen diffusion and trapping, Hydrogen desorption The trapping mechanisms for hydrogen isotopes in Al-X Cu (0.0 at. % < X < 3.5 at. %) alloys were investigated using thermal desorption spectroscopy (TDS), electrical conductivity, and differential scanning calorimetry. Constant heating rate TDS was used to determine microstructural trap energies and occupancies. In addition to the trapping states in pure Al reported in the literature (interstitial lattice sites, dislocations, and vacancies), a trap site due to Al-Cu intermetallic precipitates is observed. The binding energy of this precipitate trap is (18 ± 3) kJ&#8729;mol-1 (0.19 ± 0.03 eV). Typical occupancy of this trap is high; for Al-2.6 at. % Cu (a Cu composition comparable to that in AA2219) charged at 200 °C with 130 MPa D2 for 68 days, there is ca. there is 3.15x10-7 mol D bound to the precipitate trap per mol of Al, accounting for a third of the D in the charged sample. no NU @ karnesky @ 11513
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Vo, Nhon Q.; Dunand, David C.; Seidman, David N. Atom probe tomographic study of a friction-stir-processed Al-Mg-Sc alloy Journal Article 2012 Acta Materialia In Press Al-Mg-Sc alloy; Friction-stir process; Atom probe tomography; Strengthening The microstructure of a twin-roll-cast Al-4.5Mg-0.28Sc at.% alloy after friction-stir processing, performed at two tool rotational rates, was investigated by atom probe tomography. Outside the stir zone, the peak-aged alloy contains a high number density (~8.0 × 1023 m-3) of ~1.5 nm radius Al3Sc (L12) precipitates with a minor Mg content, providing an increase of ~600 MPa in the Vickers microhardness. In the stir zone of the sample processed at 400 rpm rotational rate, the microhardness increase is mainly due to grain refinement, rather than precipitate strengthening, because the Al3Sc precipitates, with spherical lobed cuboids and platelet-like morphology, grow and coarsen to a 10-20 nm radius. The Sc supersaturation across the stir-processed zone has a concentration gradient, which is higher on the retreating side and lower on the advancing side of the friction-stir tool. Hence, after aging at 290 °C for 22 h, the microhardness increase within the stir zone also displays a gradient due to precipitate strengthening with varying precipitate volume fractions. In the stir zone for the sample processed at 325 rpm rotational rate, the microhardness increase is also predominantly due to grain refinement, as coarse Al3Sc precipitates form heterogeneously at grain boundaries with a platelet-like morphology. The hardness remains unchanged after a 290 °C aging treatment. This is because the Al3Sc precipitates are highly heterogeneously distributed due to a combination of a small Sc supersaturation (0.05 at.%) in the matrix, the existence of dislocations, and a large area per unit volume of grain boundaries (~4-6 × 106 m-1). 1359-6454 no NU @ karnesky @ 11400
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Fuller, Christian B.; Murray, Joanne L.; Seidman, David N. Temporal Evolution of the Nanostructure of Al(Sc,Zr) Alloys: Part I—Chemical Compositions of Al[sub:3](Sc[sub:1-x]Zr[sub:x]) Precipitates Journal Article 2005 Acta Materialia Acta Mater. 53 20 5401-5413 Al-Sc-Zr alloys; Precipitation; Microstructure; High-resolution electron microscopy; Three-dimensional atom-probe microscopy Atom-probe tomography (APT) and high-resolution transmission electron microscopy are used to study the chemical composition and nanostructural temporal evolution of Al3(Sc1-xZrx) precipitates in an Al-0.09 Sc-0.047 Zr at.% alloy aged at 300C. Concentration profiles, via APT, reveal that Sc and Zr partition to Al3(Sc1-xZrx) precipitates and Zr segregates concomitantly to the &#945;-Al/Al3(Sc1-xZrx) interface. The Zr concentration in the precipitates increases with increasing aging time, reaching a maximum value of 1.5 at.% at 576 h. The relative Gibbsian interfacial excess () of Zr, with respect to Al and Sc, reaches a maximum value of 1.240.62 atoms nm-2 after at 2412 h. The temporal evolution of Al3(Sc1-xZrx) precipitates is determined by measuring the time dependence of the depletion of the matrix supersaturation of Sc and Zr. The time dependency of the supersaturation of Zr does not follow the asymptotic t-1/3 law while that of Sc does, indicating that a quasi-stationary-state is not achieved for both Sc and Zr. no NU @ karnesky @ 172
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van Dalen, M. E.; Dunand, D. C.; Seidman, D. N. Effects of Ti Additions on the Nanostructure and Creep Properties of Precipitation-Strengthened Al-Sc Alloys Journal Article 2005 Acta Materialia Acta Mater. 53 15 4225-4235 Aluminum alloys; Precipitation; Coarsening; Three-dimensional atom-probe tomography; Creep; Al-Sc Three-dimensional atom-probe tomography, transmission electron microscopy and microhardness were used to investigate the temporal evolution of nanosize, coherent Al3(Sc1&#8722;xTix) precipitates (L12 structure) in a coarse-grained Al0.06at.%Sc0.06at.%Ti alloy aged between 300 and 450 C. At 300 C, most scandium atoms partition within one day to the precipitates, whereas titanium atoms, even after 64 days of aging, remain predominantly in solid solution in the matrix, resulting in precipitates with average composition Al3(Sc0.94Ti0.06). While titanium is very effective at retarding the coarsening kinetics of the precipitates, the low levels of titanium substitution result in only modest hardness increases over the binary Al0.06at.%Sc alloy. When crept at 300 C, the peak-aged alloy exhibits a threshold stress, which when normalized by the Orowan stress, increases with increasing radius, as predicted by a recent model considering elastic interactions between dislocations and coherent precipitates, and as previously observed in AlScZr alloys. no NU @ vandalen @ 201
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Marquis, Emmanelle A.; Seidman, David N Coarsening Kinetics of Nanoscale Al[sub:3]Sc Precipitates in an Al-Mg-Sc Alloy Journal Article 2005 Acta Materialia Acta Mater. 53 15 4259-4268 Al3Sc precipitate; Morphology; Coarsening; Transmission electron microscopy; Atom-probe tomography; Al-Sc The effects of Mg alloying on the temporal evolution of Al3Sc (L12 structure) nanoscale precipitates are investigated, focusing on the morphology and coarsening kinetics of Al3Sc precipitates in an Al2.2 Mg0.12 Sc at.% alloy aged between 300 and 400 C. Approximately spheroidal precipitates are obtained after aging at 300 C and irregular morphologies are observed at 400 C. The coarsening behavior is studied using conventional and high-resolution transmission electron microscopies to obtain the temporal evolution of the precipitate radius, and atom-probe tomography is employed to measure the Sc concentration in the &#945;-matrix. The coarsening kinetics are analyzed using a coarsening model developed by Kuehmann and Voorhees for ternary systems [Kuehmann CJ, Voorhees PW. Metall Mater Trans A 1996;27:937]. Values of the interfacial free energy and diffusion coefficient for Sc diffusion in this AlMgSc alloy at 300 C are independently calculated, and are in good agreement with the calculated value of interfacial free energy [Asta M, Ozolins V, Woodward C. JOM 2001;53:16] and the experimental diffusivity obtained for the AlSc system [previous termMarquisnext term EA, previous termSeidmannext term DN. Acta Mater 2001;49:1909; previous termMarquisnext term EA. Ph.D. Thesis. Materials Science and Engineering Department, Northwestern University, 2002; Fujikawa SI. Defect Diffusion Forum 1997;143147:115]. no NU @ karnesky @ 202
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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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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&#8722;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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Fuller, Christian B.; Seidman, David N. Temporal Evolution of the Nanostructure of Al(Sc,Zr) Alloys: Part II—Coarsening of Al[sub:3]Sc[sub:1-x]Zr[sub:x] Precipitates Journal Article 2005 Acta Materialia Acta Mater. 53 20 5415-5428 Al-Sc-Zr; Phase Transformations; nanostructure; Transmission electron microscopy (TEM), The coarsening behavior of four Al(Sc,Zr) alloys containing small volume fractions (< 0.01) of Al3(Sc1-xZrx) (L12) precipitates was investigated employing conventional transmission electron microscopy (CTEM) and high-resolution electron microscopy (HREM). The activation energies for diffusion-limited coarsening were obtained employing the Umantsev-Olson-Kuehmann-Voorhees (UOKV) model for multi-component alloys. The addition of Zr is shown to retard significantly the coarsening rate and stabilize precipitate morphologies. HREM of Al(Sc,Zr) alloys aged at 300C reveals Al3(Sc1-xZrx) precipitates with sharp facets parallel to {100} and {110} planes. Coarsening of Al-0.07 Sc-0.019 Zr at.%, Al-0.06 Sc-0.005 Zr at.%. and Al-0.09 Sc-0.047 Zr at.% alloys is shown to be controlled by volume diffusion of Zr atoms, while coarsening of Al-0.14 Sc-0.012 Zr et al. is controlled by volume diffusion of Sc atoms. no NU @ karnesky @ 235
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