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Type Chao, Paul; Karnesky, Richard A.
  Publication Hydrogen Isotope trapping in Al-Cu binary alloys Volume (down) Journal Article
Pages 2016
  Abstract Materials Science & Engineering A  
  Corporate Author Mater Sci Eng A  
Publisher 658  
Editor
  Summary Language 422-428 Series Editor Age-hardening, Aluminium alloys, Al-Cu, Hydrogen diffusion and trapping, Hydrogen desorption  
Abbreviated Series Title 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.
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no NU @ karnesky @ 11513
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Harada, Yoshihisha; Dunand, David C. Microstructure and Hardness of Scandium Trialuminide with Ternary Rare-Earth Additions Journal Article 2007 Materials Science Forum Mater. Sci. Forum 539-543 1565-1570 Microstructure, Micro-hardness, Lattice parameter, Al3Sc, Scandium, Rare-earth, SEM/EDS, X-ray diffraction; Al-Sc The microstructure of ternary Al3(Sc1-yREy) intermetallic compounds (where RE is one of the rare-earth elements La, Ce, Nd, Sm, Eu, Yb or Lu), was investigated as a function of RE concentration for 0<y&#8804;0.75. Alloys with La, Ce, Nd, Sm or Eu additions consist of a L12 phase containing a dendritic second phase with D019 (La, Ce, Nd, Sm) or C11b (Eu) structure. Alloys with Yb or Lu additions show a single L12 phase. The RE solubility limits at 1373 K in the L12-Al3(Sc1-yREy) phase are very low for La, Nd, Ce and Eu (0.08-0.41 at.% or y=0.0032-0.0164), low for Sm (3.22 at.% or y=0.1288) and complete for Yb and Lu. The lattice parameter of the L12 solid-solution increases linearly with RE concentration and the magnitude of this effect is correlated with the atomic size mismatch between Sc and the RE elements. The Vickers micro-hardness of the L12 solid-solution increases linearly with increasing RE concentration. no NU @ karnesky @ 1833
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Beeri, Ofer; Dunand, David C.; Seidman, David N. Role of Impurities on Precipitation Kinetics of Dilute Al-Sc alloys Journal Article 2010 Materials Science and Engineering A 527 15 3501-3509 Dilute aluminum alloys, Scandium, Precipitation, Impurities, Atom Probe; Al-Sc High purity (HP) aluminum and commercial purity (CP) aluminum (major impurities: ~250 at. ppm Si and ~130 at. ppm Fe) are alloyed with ~250 to ~1100 at. ppm Sc and ~50 at. ppm RE (RE = La, Ce, Pr, or Nd). The alloys are homogenized at 640 &#61616;C and aged at 300 &#61616;C. The precipitation kinetics, basic mechanical properties, and microstructure are studied using AC electrical conductivity, microhardness measurements, scanning electron microscopy in conjunction with energy dispersive x-ray spectroscopy, and atom-probe tomography, respectively. The Fe and RE elements form micrometer-scale diameter Al~3(Fe,RE) primary precipitates, which have no effect on the mechanical properties. Silicon accelerates the precipitation kinetics of nanometer-scale diameter Al3Sc precipitates, increasing their number density, thereby resulting in a higher microhardness values for CP aluminum than the HP aluminum having the same Sc concentration. Additionally, the Sc equilibrium solubility in the &#61537;-Al matrix is estimated and Orowan's strengthening mechanism is confirmed for the Al3Sc precipitates. no NU @ karnesky @ 10742
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Karnesky, Richard A.; Seidman, David N.; Dunand, David C. Creep of Al-Sc Microalloys with Rare-Earth Element Additions Journal Article 2006 Materials Science Forum Mater. Sci. Forum 519-521 1035-1040 Scandium, Rare-Earth Elements, Creep, Precipitation Strengthening; Al-Sc Cast and aged Al-Sc microalloys are creep-resistant to 300C, due to the blocking of dislocations by nanosize, coherent Al[sub:3]Sc (L1[sub:2]) precipitates. Rare-earth elements substitute for Sc in these precipitates, leading to a higher number density of smaller precipitates, which have a greater lattice-parameter mismatch with Al than in the Al-Sc binary microalloy. This leads to an improvement in both ambient temperature microhardness and high temperature creep. Creep threshold stresses of Al-Sc-RE (RE = Y, Dy, or Er) at 300C; are higher than for Al-Sc and Al-Sc-M (M = Mg, Ti, or Zr) microalloys. This is in agreement with a dislocation climb model that includes the elastic stress fields of the precipitates. ICAA10 no NU @ karnesky @ 660
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Fuller, Christian B.; Krause, Albert R.; Dunand, David C.; Seidman, David N. Microstructure and Mechanical Properties of a 5754 Aluminum Alloy Modified by Sc and Zr Additions Journal Article 2002 Materials Science and Engineering A Mater. Sci. Eng. A 338 1-2 8-16 Al-Sc-Zr alloys; Fatigue (materials); Mechanical properties; Aluminum alloys; Microstructural properties The effects of various heat treatments upon the microstructure and mechanical properties of a rolled 5754 aluminum alloy modified with 0.23 wt.% Sc and 0.22 wt.% Zr were investigated. Grain size, as well as precipitate size, type, and morphology were observed by optical and transmission electron microscopies. Two populations of the Al3Sc1-xZrx phase were present: (i) large incoherent precipitates formed during solidification and hot-rolling; and (ii) fine coherent precipitates formed from secondary precipitation, which improved alloy strength, as shown by hardness, tensile, and fatigue measurements. Aging, however, also produced two types of grain-boundary precipitates, Al6Mn and -Al3Mg2, which contributed to poorer fatigue behavior and reduced ductility. no NU @ karnesky @ 526
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Harada, Y.; Dunand, D.C. Microstructure of Al[sub:3]Sc with Ternary Transition-Metal Additions Journal Article 2002 Materials Science and Engineering A Mater. Sci. Eng. A 329-331 686-695 L12-trialuminides; Microstructure; Lattice parameter; Microhardness; Al-Sc The microstructure of binary Al3Sc and ternary Al3(Sc1-yXy), where X is one of the transition metals from Group IIIA (Y), IVA (Ti, Zr or Hf) or VA (V, Nb or Ta), was investigated as a function of alloying element concentration for 0.1y0.75. Alloys with Group IIIA and IVA additions exhibited a single L12 solid-solution phase with some Kirkendall porosity. At the highest concentration studied, a second phase precipitated with the D019 (Y), D022 (Ti) or D023 (Zr and Hf) structure. Conversely, alloys with Group VA additions exhibited both the L12 trialuminide phase and a dendritic trialuminide second phase with D022 structure for all concentrations studied. The solubility limit in the ternary L12-type Al3(Sc1-yXy) phase was high for Group IIIA and IVA metals (almost 12.5 at.% or y=0.5), and much lower for Group VA metals (from about 1.8 at.% or y=0.07 for Ta to about 2.7 at.% or y=0.11 for V). Similarly, the solubility limit of Sc in the non-L12 phases decreases from the Group IIIA trialuminide to the Group VA trialuminides. The lattice parameter of the L12 solid-solution decreased linearly with increasing concentration of Group IVA and VA metals, but increased linearly with concentration of Y (Group IIIA). This linear concentration dependence of the lattice parameter is found to correlate with the atomic size mismatch between Sc and the transition metal. The microhardness of the L12 solid-solution increased linearly with increasing concentration of ternary elements. The concentration dependence of hardness is strongest for Group VA metals and weakest for Group IVA metals, for which a correlation is found with the concentration dependence of lattice parameter. no NU @ karnesky @ 543
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Biswas, Aniruddha; Siegel, Donald J.; Seidman, David N. Simultaneous Segregation at Coherent and Semi-coherent Heterophase Interfaces Journal Article 2010 Physical Review Letters 105 7 076102-76103 Al-Cu Employing a combination of three-dimensional atom-probe tomography and first-principles calculations, significant qualitative and quantitative differences in solute segregation at coherent and semi-coherent interfaces bounding a single &#952;'-precipitate in an Al-Cu-based alloy are found. Qualitatively, localized segregation is observed at the semi-coherent interface, whereas delocalized behavior is present at the coherent facets. Quantitatively, segregation at the semi-coherent interface is a factor of two greater than at the coherent interface, resulting in a decrease in interfacial energy that is more than five times greater than that observed at the coherent facet. These observations illustrate unambiguously the strong couplings among interface structure, chemical composition, and energetics. no NU @ karnesky @ 10810
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Knipling, Keith E.; Dunand, David C.; Seidman, David N. Criteria for Developing Castable, Creep-Resistant Aluminum-Based Alloys–A Review Journal Article 2006 Zeitschrift für Metallkunde Z. Metallkd 97 3 246-265 Aluminum alloys; Trialuminides; Precipitation strengthening; Creep; Al-Sc We describe four criteria for the selection of alloying elements capable of producing castable, precipitation-strengthened Al alloys with high-temperature stability and strength: these alloying elements must (i) be capable of forming a suitable strengthening phase, (ii) show low solid solubility in Al, (iii) showlow diffusivity in Al, and (iv) retain the ability for the alloy to be conventionally solidified. With regard to criterion (i), we consider those systems forming Al3Mtrialuminide compounds with a cubic L12 crystal structure, which are structurally analogous to Ni3Al ( 0) in the Ni-based superalloys. Eight elements, clustered in the same region of the periodic table, fulfill criterion (i): the first Group 3 transition metal (Sc), the three Group 4 transition metals (Ti, Zr, Hf) and the four latest rare-earth elements (Er, Tm, Yb, Lu). Based on a review of the existing literature, these elements are discussed in terms of criteria (ii) and (iii), which satisfy the need for a dispersion in Al with slow coarsening kinetics, and criteria (iv), which is discussed based on the binary phase diagrams. no NU @ karnesky @ 236
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Krug, ME; Dunand, DC; Seidman, DN Composition Profiles within Al3Li and Al3Sc/Al3Li Nanoscale Precipitates in Aluminum Journal Article 2008 Applied Physics Letters App. Phys. Let. 92 124107-1 - 124107-3 Al; Sc; Li; Aluminum; Scandium; Lithium; Core-shell Precipitates; Al-Sc An Al–11.3Li–0.11Sc (at. %) alloy was double-aged to induce first Alpha'-Al3Sc and then delta'-Al3Li precipitates. Atom-probe tomography revealed both single-phase delta'-precipitates and core-shell alpha'/delta'-precipitates (with respective average radii of 16 and 27 nm, and respective volume fractions of 12 and 9%) conferring a high strength to the alloy. Although the delta'-shells contain little Sc (~0.027 at. %), the alpha'-cores have a high Li content, with an average composition of Al0.72(Sc0.17Li0.11). The Li concentrations within the delta'-phase and the Li interfacial excess at the delta'/alpha'-interface both exhibit wide precipitate-to-precipitate variations. no NU @ m-krug @ 10263
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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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