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Title Fuller, Christian B.; Seidman, David N.; Dunand, David C.
Year Creep Properties of Coarse-Grained Al(Sc) Alloys at 300°C
Abbreviated Journal Journal Article
Issue 1999 Keywords Scripta Materialia
Address Scripta Mater.
Thesis 40
Place of Publication 6 Language 691-696
Original Title Al-Sc
Series Title Series Volume
Serial Orig Record
no NU @ karnesky @ 527
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Harada, Y.; Dunand, D.C. Microstructure of Al[sub:3]Sc with ternary rare-earth additions Journal Article 2009 Intermetallics 17 1-2 17-24 Al-Sc; Trialuminides; Rare-earth intermetallics; Solid-solution hardening; Microstructure; Diffraction The microstructure of ternary L1[sub:2]-Al[sub:3](Sc[sub:1-y]RE[sub:y]) intermetallics, where RE is one of the rare-earth elements selected from five light (La, Ce, Nd, Sm or Eu) or two heavy lanthanoids (Yb or Lu), was investigated as a function of RE concentration for 0.02 <= y <= 0.75. Alloys with light RE show two phases: L1[sub:2]-Al[sub:3](Sc,RE) and D0[sub:19]-Al[sub:3](RE,Sc) (or C11[sub:b]-Al[sub:4](Eu,Sc)). Alloys with heavy RE exhibit a single L1[sub:2]-Al[sub:3](Sc,RE) phase. The maximum RE solubility in the L1[sub:2] phase is very low (<0.4 at.%) for La, Ce, Nd and Eu, low (3.2 at.%) for Sm and complete solid-solution for Yb and Lu. Both lattice parameter and hardness of the L1[sub:2]-Al[sub:3](Sc,RE) phases increase linearly with Sm, Yb or Lu concentration, and the magnitude of both effects correlates with the atomic size mismatch between Sc and RE. no NU @ karnesky @ 10536
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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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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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Harada, Y.; Dunand, D.C. Microstructure and Creep Properties of Al[sub:3]Sc with Ternary Transition Metal Additions Book Chapter 2001 The 7th International Conference on Creep and Fatigue at Elevated Temperature (Creep VII) 219-226 Al-Sc Japan Society of Mechanical Engineers no NU @ karnesky @ 1904
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Harada, Y.; Dunand, D.C. Creep Properties of Al[sub:3]Sc and Al[sub:3](Sc, X) Intermetallics Journal Article 2000 Acta Materialia Acta Mater. 48 13 3477-3487 Journal Article; Aluminum compounds, Mechanical properties; Scandium compounds, Mechanical properties; Intermetallics, Mechanical properties; Titanium, Alloying additive; Yttrium, Alloying additive; Zirconium, Alloying additive; Hafnium, Alloying additive; Creep (materials), Alloying effects; Dislocation mobility, Deformation effects; Al-Sc; mechanical properties creep intermetallic compounds bulk diffusion scandium microstructure high-temperature creep l12 trialuminides self-diffusion behavior fracture films al3ti compression chromium aluminum A systematic creep study was undertaken for the binary intermetallic Al sub 3 Sc and the ternary single-phase intermetallic Al sub 3 (Sc sub 0.74 X sub 0.26 ), where X is one of the transition-metals Ti, Y, Zr or Hf. Creep tests were conducted in the temperature range from 673-1200K under a constant compressive stress ranging from 30-300 MPa. The binary Al sub 3 Sc exhibits a stress exponent of 4.4-4.9 indicative of creep controlled by climb of dislocations. The activation energy for creep of Al sub 3 Sc was 128plus/minus6 kJ/mol, close to that for self-diffusion for pure aluminum, in agreement with the Cu sub 3 Au rule, indicating that diffusion on the Al-sublattice is controlling. Ternary Al sub 3 (Sc sub 0.74 X sub 0.26 ) exhibits a decrease in creep rate by about one order of magnitude for Zr and Hf and by about two orders of magnitude for Ti and Y. For all ternary alloys, a stress exponent of 3.9-5.5 was observed, indicative of dislocation creep. Activation energies for creep of 202plus/minus8 kJ/mol were found, showing that ternary substitution for scandium with transition metals affects diffusion on the Al sublattice. Northwestern University (Evanston); Ministry of International Trade and Industry (Japan) English 1359-6454 37 ref., Photomicrographs, Graphs, Numerical Data no NU @ karnesky @ 544
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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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Karnesky, Richard A. Mechanical Properties and Microstructure of Al–Sc with Rare-Earth Element or Al[sub:2]O[sub:3] Additions Book Whole 2007 258 Al-Sc Aluminum alloys strengthened with coherent (L1[sub:2]), nanosize Al[sub:3]Sc precipitates are structural materials that have outstanding strength at ambient and elevated temperatures. They are creep resistant at 300 °C and exhibit a threshold stress, below which creep is not measurable. Introducing ternary alloying additions, such as rare-earth elements (RE=Y, Dy, Er), that segregate within Al[sub:3]Sc precipitates improves this creep resistance by increasing the lattice parameter misfit of precipitates with Al. In this thesis, Al–600 Sc–200 RE and Al–900 Sc–300 Er (at. ppm) are studied. These elements are an order of magnitude less expensive than Sc, so reduce alloy costs. As an alternative or supplement to ternary additions, submicron (incoherent) Al[sub:2]O[sub:3] dispersoids impart additional strengthening. The dispersion-strengthened cast alloys, DSC–Al–1100 Sc and DSC–Al–800 Sc–300 Zr, studied in this thesis contain 30 vol.% Al[sub:2]O[sub:3]. In this thesis, the temporal evolution of Al–Sc–RE and DSC–Al–Sc(–Zr) alloys are measured using Local-Electrode Atom-Probe (LEAP) tomography, conventional transmission electron microscopy, and electrical conductivity. These techniques measure the changes in precipitate number density, size, volume fraction, chemical composition, and interprecipitate distance and are compared to models. They are also employed to measure the diffusivity and solid solubility of Er in Al in Al–300 Er, Al–450 Er, and Al–600 Er. The mechanical behavior (microhardness, yield, and creep) of the alloys is studied at 25, 300, and 350 °C. The effect of Al[sub:3](Sc[sub:1-x]Er[sub:x]) precipitate size and interprecipitate distance is studied by varying isochronal and isothermal aging treatments. Various models and simulations are compared to experimental data. At ambient temperatures, very small Al[sub:3](Sc[sub:1-x]M[sub:x]) precipitates contribute to order strengthening and larger (unshearable) precipitates are bypassed by dislocations through Orowan bowing. Dislocation dynamics simulations allow both processes to operate in a glide plane, where precipitate distributions may be gathered directly or be informed by LEAP tomography data. At elevated temperatures, the lattice parameter and modulus mismatches of Al[sub:3](Sc[sub:1-x]M[sub:x]) oppose both dislocation climb over Al[sub:3](Sc[sub:1-x]M[sub:x]) and dislocation detachment from Al[sub:2]O[sub:3]. Northwestern University Ph.D. thesis Evanston, IL English no NU @ karnesky @ 10000
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Karnesky, Richard A.; Dunand, David C.; Seidman, David N. Evolution of Nanoscale Precipitates in Al Microalloyed with Sc and Er Journal Article 2009 Acta Materialia Acta Mater. 57 14 4022-4031 Aluminum alloys; Rare-earth elements; Scandium; Precipitation; Coarsening; Al-Sc-Er The coarsening kinetics of nanoscale, coherent Al[sub:3](Sc[sub:1-x]Er[sub:x]) precipitates in [alpha]–Al during aging of a supersaturated Al–0.06 Sc–0.02 Er (at.%) alloy at 300 °C are studied using transmission electron microscopy and local-electrode atom-probe tomography. Erbium and Sc segregate at the precipitate core and shell, respectively. The matrix supersaturations of Er and Sc, as well as the mean precipitate radius and number density evolve in approximate agreement with coarsening models, allowing the determination of the matrix/precipitate interfacial free energy and solute diffusivities. At 300 °C, the [alpha]–Al/Al[sub:3](Sc[sub:1-x]Er[sub:x]) interfacial free energy due to Sc is about twice as large as for [alpha]–Al/Al[sub:3]Sc. The diffusivity of Er in the ternary alloy is about three orders of magnitude smaller than that of Er in binary Al–0.045 at.% Er and about two orders of magnitude smaller than the diffusivity of Sc in binary Al–Sc. The measured Sc diffusivity is consistent with literature values. no NU @ karnesky @ 10599
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Karnesky, Richard A.; Meng, Liang; Dunand, David C. Strengthening Mechanisms in Aluminum Containing Coherent Al[sub:3]Sc Precipitates and Incoherent Al[sub:2]O[sub:3] Dispersoids Journal Article 2007 Acta Materialia Acta Mater. 55 4 1299-1308 Metal Matrix Composites; Precipitation; Aluminium Alloys; Creep; Zirconium; Al-Sc Dispersion-strengthened-cast aluminum (DSC-Al), consisting of a coarse-grained aluminum matrix containing two populations of particles (30 vol.% of 300 nm Al[sub:2]O[sub:3] incoherent dispersoids and 0.2-0.3 vol.% of 6-60 nm coherent Al[sub:3]Sc precipitates), was studied. At ambient and elevated temperatures, both populations of particles contribute to strengthening. At 300 °C, creep threshold stresses are considerably higher than for control materials with a single population of either Al[sub:2]O[sub:3] dispersoids or Al[sub:3]Sc precipitates. This synergistic effect is modeled by considering dislocations pinned at the departure side of incoherent Al[sub:2]O[sub:3] dispersoids (detachment model) and simultaneously subjected to elastic interactions from neighboring coherent Al[sub:3Sc precipitates. no NU @ karnesky @ 1782
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