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Knipling, Keith E.; Dunand, David C.; Seidman, David N. |
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Criteria for Developing Castable, Creep-Resistant Aluminum-Based Alloys–A Review |
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Journal Article |
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2006 |
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Abstract |
Zeitschrift für Metallkunde |
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Z. Metallkd |
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97 |
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3 |
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Summary Language |
246-265 |
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Aluminum alloys; Trialuminides; Precipitation strengthening; Creep; Al-Sc |
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Abbreviated Series Title |
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. |
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NU @ karnesky @ |
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236 |
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Marquis, Emmanuelle A.; Seidman, David N.; Asta, Mark; Woodward, Christopher |
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Composition Evolution of Nanoscale Al[sub:3]Sc Precipitates in an Al-Mg-Sc Alloy: Experiments and Computations |
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Journal Article |
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2006 |
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Acta Materialia |
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Acta Mater. |
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54 |
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1 |
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119-130 |
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Atom-probe tomography; Ab initio calculations; Al3Sc precipitates; Mg segregation; Coherent heterophase interface; Al-Sc |
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Controlling the distribution of chemical constituents within complex, structurally heterogeneous systems represents one of the fundamental challenges of alloy design. We demonstrate how the combination of recent developments in sophisticated experimental high resolution characterization techniques and ab initio theoretical methods provide the basis for a detailed level of understanding of the microscopic factors governing compositional distributions in metallic alloys. In a study of the partitioning of Mg in two-phase ternary AlScMg alloys by atom-probe tomography, we identify a large Mg concentration enhancement at the coherent α-Al/Al3Sc heterophase interface with a relative Gibbsian interfacial excess of Mg with respect to Al and Sc, Click to view the MathML source, equal to 1.9 0.5 atom nm−2. The corresponding calculated value of Click to view the MathML source is not, vert, similar1.2 atom nm−2. Theoretical ab initio investigations establish an equilibrium driving force for Mg interfacial segregation that is primarily chemical in nature and reflects the strength of the MgSc interactions in an Al-rich alloy. |
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NU @ karnesky @ |
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260 |
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Fuller, Christian B.; Krause, Albert R.; Dunand, David C.; Seidman, David N. |
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Microstructure and Mechanical Properties of a 5754 Aluminum Alloy Modified by Sc and Zr Additions |
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Journal Article |
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2002 |
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Materials Science and Engineering A |
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Mater. Sci. Eng. A |
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338 |
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1-2 |
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8-16 |
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Al-Sc-Zr alloys; Fatigue (materials); Mechanical properties; Aluminum alloys; Microstructural properties |
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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. |
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NU @ karnesky @ |
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526 |
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Fuller, Christian B.; Seidman, David N.; Dunand, David C. |
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Creep Properties of Coarse-Grained Al(Sc) Alloys at 300°C |
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Journal Article |
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1999 |
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Scripta Materialia |
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Scripta Mater. |
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40 |
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6 |
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691-696 |
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Al-Sc |
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NU @ karnesky @ |
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527 |
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Karnesky, Richard A.; Meng, Liang; Seidman, David N.; Dunand, David C. |
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Mechanical Properties of a Heat-Treatable Al-Sc Alloy Reinforced with Al[sub:2]O[sub:3] |
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Book Chapter |
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2003 |
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Affordable Metal-Matrix Composites for High Performance Applications II |
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215-224 |
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Aluminum alloys, Scandium, Alumina, Mechanical properties, Precipitation strengthening, Dispersoid strengthening, Threshold stress; Al-Sc |
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The mechanical behavior of precipitation-strengthened Al-0.18 wt.% Sc alloys containing 30 vol.% Al[sub:2]O[sub:3] dispersoids is studied at 25, 300 and 350°C. The effect of Al[sub:3]Sc precipitate size is studied by varying aging treatments. Microhardness measurements show that both populations of particles (nanometer-sized Al[sub:3]Sc precipitates and submicron-sized Al[sub:2]O[sub:3] dispersoids) contribute to strength at ambient temperature. At elevated temperature, a threshold stress is observed, indicative of interactions between matrix dislocations and the particles. The threshold stress is significantly higher than either Al-0.18 wt.% Sc alloys without Al[sub:2]O[sub:3] dispersoids or Al-30 vol.% Al[sub:2]O[sub:3] without Al[sub:3]Sc precipitates. This indicates that strengthening is occurring at both length scales and in a nonlinear manner, as the reinforced alloy exhibits strength higher than the sum of the strengths of Al-Sc and Al-Al[sub:2]O[sub:3] alloys. |
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Northwestern University |
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TMS |
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Chicago |
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Awadh B. Pandey, Kevin L. Kendig, John Lewandowski, and Sandeep R. Shah |
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English |
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0-87339-557-3 |
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Materials Science & Technology 2003 |
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NU @ karnesky @ |
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528 |
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Harada, Y.; Dunand, D.C. |
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Thermal Expansion of Al[sub:3]Sc and Al[sub:3](Sc[sub:0.75]X[sub:0.25]) |
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Journal Article |
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2003 |
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Scripta Materialia |
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Scripta Mater. |
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48 |
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3 |
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219-222 |
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intermetallic compound aluminum alloys thermal expansion scandium physical-properties al(sc) alloys |
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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 |
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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 |
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....there is an error: we should have written : alloying the matrix with magnesium, which INCREASES the lattice constant of Al ... |
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NU @ karnesky @ |
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542 |
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Harada, Y.; Dunand, D.C. |
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Microstructure of Al[sub:3]Sc with Ternary Transition-Metal Additions |
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Journal Article |
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2002 |
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Materials Science and Engineering A |
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Mater. Sci. Eng. A |
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329-331 |
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686-695 |
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L12-trialuminides; Microstructure; Lattice parameter; Microhardness; Al-Sc |
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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. |
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NU @ karnesky @ |
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543 |
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Harada, Y.; Dunand, D.C. |
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Creep Properties of Al[sub:3]Sc and Al[sub:3](Sc, X) Intermetallics |
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Journal Article |
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2000 |
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Acta Materialia |
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Acta Mater. |
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48 |
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13 |
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3477-3487 |
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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 |
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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. |
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Northwestern University (Evanston); Ministry of International Trade and Industry (Japan) |
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English |
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1359-6454 |
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37 ref., Photomicrographs, Graphs, Numerical Data |
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NU @ karnesky @ |
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544 |
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Marquis, E. A.; Seidman, D. N. |
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Nanoscale Structural Evolution of Al[sub:3]Sc Precipitates in Al(Sc) Alloys |
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Journal Article |
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2001 |
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Acta Materialia |
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Acta Mater. |
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49 |
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11 |
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1909-1919 |
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aluminum scandium transmission electron microscopy (tem) phase transformations microstructure al-sc alloys creep-properties nucleation scandium aluminum intermetallics kinetics growth energy; Al-Sc |
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Precipitation of the Al3Sc (L12) phase in aluminum alloys, containing 0.1, 0.2 or 0.3 wt% Sc, is studied with conventional transmission and high-resolution (HREM) electron microscopies. The exact morphologies of the Al3Sc precipitates were determined for the first time by HREM, in Al–0.1 wt% Sc and Al–0.3 wt% Sc alloys. The experimentally determined equilibrium shape of the Al3Sc precipitates, at 300°C and 0.3 wt% Sc, has 26 facets, which are the 6 {100} (cube), 12 {110} (rhombic dodecahedron), and 8 {111} (octahedron) planes, a Great Rhombicuboctahedron. This equilibrium morphology had been predicted by first principles calculations of the pertinent interfacial energies. The coarsening kinetics obey the (time)1/3 kinetic law of Lifshitz–Slyozov–Wagner theory and they yield an activation energy for diffusion, 164±9 kJ/mol, that is in agreement with the values obtained from tracer diffusion measurements of Sc in Al and first principles calculations, which implies diffusion-controlled coarsening. |
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Seidman, D. N. Northwestern Univ, Dept Mat Sci & Engn, 2225 N Campus Dr, Evanston, IL 60208 USA Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA |
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NU @ karnesky @ |
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568 |
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Marquis, Emmanuelle A.; Dunand, David C. |
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Model for Creep Threshold Stress in Precipitation-Strengthened Alloys with Coherent Particles |
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Journal Article |
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2002 |
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Scripta Materialia |
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Scripta Mater. |
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47 |
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8 |
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503-508 |
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creep threshold stress precipitation strengthening aluminum alloys dislocation mobility al(sc) alloys al3sc; Al-Sc |
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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. |
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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 |
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NU @ karnesky @ |
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569 |
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