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Type (up) Harada, Y.; Dunand, D.C.
  Publication Microstructure and Creep Properties of Al[sub:3]Sc with Ternary Transition Metal Additions Volume Book Chapter
Pages 2001
  Abstract The 7th International Conference on Creep and Fatigue at Elevated Temperature (Creep VII)  
  Corporate Author  
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  Summary Language 219-226 Series Editor Al-Sc  
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  Series Issue ISSN  
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  Expedition Japan Society of Mechanical Engineers Notes  
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no NU @ karnesky @ 1904
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Fuller, Christian B.; Seidman, David N.; Dunand, David C. Structure-Property Relationships for Al(Sc,Zr) Alloys Book Chapter 2003 Hot Deformation of Aluminum Alloys III 531-540 Al-Sc TMS Warrendale, PA Zin, J.; Beaudoin, A.; Bieler, T. A.; Radhakrishnan, B. no NU @ karnesky @ 1907
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Marquis, E. A.; Seidman, D. N; Dunand, D. C. Microstructural, and Creep Properties of an Al-2 Mg-0.2 Sc (wt.%) Alloy Book Chapter 2003 Hot Deformation of Aluminum Alloys III 177-184 Al-Sc TMS Warrendale, PA Zin, J.; Beaudoin, A.; Bieler, T. A.; Radhakrishnan, B. no NU @ karnesky @ 1906
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Marquis, E. A.; Seidman, D. N.; Dunand, D. C. Creep of Precipitation-Strengthened Al(Sc) Alloys Book Chapter 2002 Creep Deformation: Fundamentals and Applications 299-308 Al-Sc TMS Warrendale, PA Mishra, Rajiv S.; Earthman, James C.; ;Raj, Sai V. 0873395158 no refbase @ user 1384
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van Dalen, Marsha E.; Dunand, David C.; Seidman, David N. Precipitation Strengthening in Al (Sc,Ti) Alloys Book Chapter 2003 Affordable Metal-Matrix Composites for High Performance Applications II 195-201 Al-Sc-Ti alloys; Precipitation hardening; Microstructure; Three-dimensional atom-probe microscopy Three-dimensional atom probe (3DAP) and field-ion microscopies, together with microhardness measurements, are employed to analyze Al3(Sc1-xTix) precipitates in an Al-0.06at%Sc-0.06at.%Ti alloy aged at 300°C for different times. The field-ion microscope images show a relatively high number density of precipitates (estimated at (3±2)×1021ppt m-3) at the aging times analyzed. Concentration profiles obtained with 3DAP microscopy show that both Sc and Ti partition to these precipitates. While most of the Sc is contained in the precipitates, the Ti resides mainly in the matrix in solid solution. Consequently, the addition of Ti increases the hardness of this alloy only modestly over that of binary Al-Sc alloys. Additionally, the coherent Al3(Sc1-xTix) precipitates remain stable and coarsening-resistant up to aging times of at least 240 hr. at 300°C. Northwestern University; Northwestern University TMS Chicago English 0-87339-557-3 Materials Science & Technology 2003 no NU @ karnesky @ 570
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Karnesky, Richard A.; Meng, Liang; Seidman, David N.; Dunand, David C. Mechanical Properties of a Heat-Treatable Al-Sc Alloy Reinforced with Al[sub:2]O[sub:3] Book Chapter 2003 Affordable Metal-Matrix Composites for High Performance Applications II 215-224 Aluminum alloys, Scandium, Alumina, Mechanical properties, Precipitation strengthening, Dispersoid strengthening, Threshold stress; Al-Sc 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. Northwestern University TMS Chicago Awadh B. Pandey, Kevin L. Kendig, John Lewandowski, and Sandeep R. Shah English 0-87339-557-3 Materials Science & Technology 2003 no NU @ karnesky @ 528
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Fuller, Christian B. Temporal Evolution of the Microstructures of Al(Sc,Zr) Alloys and Their Influences on Mechanical Properties Book Whole 2003 179 Al-Sc Al(Sc) alloys represent a new class of potential alloys for aerospace and automotive applications. These alloys have superior mechanical properties due to the presence of fine, coherent, unshearable Al3Sc precipitates, which form upon the decomposition of an supersaturated Al(Sc) solid-solution. Additions of Zr to Al(Sc) are found to improve alloy strength and coarsening resistance, but the operating mechanisms are not well understood. In this thesis, the relationships between the mechanical and microstructural properties of Al(Sc,Zr) alloy are presented. Three-dimensional atom probe microscopy (3DAP) and conventional and high-resolution transmission electron microscopies (CTEM and HREM) are utilized to study the temporal evolution of Al3Sc1-xZrx (L12 structure) precipitates in dilute Al(Sc,Zr) alloys (precipitate volume fractions < 1%) aged between 300 and 375°C. Concentration profiles, obtained with 3DAP, show Sc and Zr to partition to Al3Sc1-xZrx precipitates, and Zr to segregate near the Al/Al3Sc1-xZrx interface. CTEM and 3DAP are utilized to determine the temporal evolution of Al(Sc,Zr) alloys, which is discussed employing diffusion-limited coarsening theories. Zirconium additions are found to retard the precipitate coarsening kinetics and stabilize precipitate morphologies. Mechanical properties of Al(Sc,Zr) alloys are investigated utilizing Vicker’s microhardness and creep. Deformation at ambient-temperature is explained by classic precipitation-strengthening mechanisms, where a transition between precipitate shearing and Orowan looping is calculated to occur at an average precipitate radius, <r>, of 2-3 nm. Al(Sc,Zr) alloys deformed by creep at 300°C are found to exhibit a climb controlled threshold stress, which is shown to increase with <r>, in agreement with previous results in Al(Sc) alloys and a previous general climb model considering the interaction between dislocations and coherent misfitting precipitates. Finally, the effect 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 are investigated. The presence of the Al3Sc1-xZrx precipitates is found to improve the alloy strength, by pinning subgrain and grain boundaries, as shown by hardness, tensile, and fatigue measurements. Northwestern University Ph.D. thesis no NU @ karnesky @ 147
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Marquis, Emmanuelle A. Microstructural Evolution and Strengthening Mechanisms in Al-Sc and Al-Mg-Sc Alloys Book Whole 2002 223 Al-Sc Al-Sc alloys are potential candidates for structural industrial applications because of their excellent mechanical properties due to the presence of small, coherent Al3Sc (L12 structure) precipitates that are formed during aging. Additional Mg alloying not only enhances the mechanical properties by solid-solution hardening but also provides corrosion resistance and better weldability. Understanding and controlling the microstructure, i.e. the temporal evolution of the Al3Sc precipitate morphologies and the effects of other alloying elements such as Mg, are critical for optimizing mechanical properties. First, this research aims at describing the microstructural evolution of the Al3Sc precipitates during aging using transmission electron microscopies. The effects of Mg additions on precipitation are described using high-resolution transmission electron microscopy observations and three-dimensional atom-probe microscopy analyses.Results on Mg segregation, on the nanoscale level, at the coherent Al / Al3Sc interface are presented. A second goal of this research is to understand the precipitation-strengthening parameters controlling optimal yield strength at room temperature and creep resistance at elevated temperature (0.6 Tm), the effects of precipitate size and volume fraction upon yield and creep strengths of dilute Al-Sc and Al-Mg-Sc alloys are studied. Room temperature strength is described in terms of precipitate shearing and Orowan dislocation looping. Creep threshold stresses are found to be about ten times lower than the yield stresses at 300°C, indicative of a climb-controlled bypass mechanism, which is modeled by extending existing dislocation-particle interaction models. Northwestern University Ph.D. thesis no NU @ karnesky @ 151
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Krug, Matthew E. Microstructural Evolution and Mechanical Properties in Al-Sc Alloys With Li and Rare Earth Additions Book Whole 2011 372 Al-Sc, Al-Li, Al-Li-Sc, rare earth, LEAP, atom probe Aluminum-scandium alloys have excellent mechanical properties at ambient and elevated temperatures due to the presence of coherent, nano-scale, L12-ordered Al3Sc precipitates. In this thesis, a variety of Al-Sc alloys with additions of Li and RE elements, primarily Yb, are studied. An addition of ytterbium reduces the cost of Al-Sc alloys by replacing some of the more-expensive Sc. Lithium is a unique alloying addition to Al-Sc alloys, because it has significant solubility in both the matrix and precipitate phases. Lithium also provides solid solution strengthening, and a large strengthening increment on aging through the formation of Al3Li precipitates. The effects of these alloying additions on Al-Sc alloys are investigated in detail, and discussed in the context of physical models linking the microstructure to measured mechanical properties. The alloys undergo a variety of aging treatments between 170 – 450 °C, producing a range of precipitate distributions. Their aging response is assessed using Vickers microhardness to monitor ambient-temperature strength, and electrical conductivity to monitor the progress of the precipitation reaction. The alloys are creep-tested in compression at 300 °C, and exhibit threshold stresses, below which no measurable creep occurs. Detailed microstructural investigations rely primarily on local electrode atom probe tomography, as well as transmission electron microscopy. The volume fractions, number densities, and chemical compositions of precipitates are measured at the nano-scale, and their size and spatial distributions are quantitatively determined. Compared to binary Al-Sc alloys, Al-Li-Sc and Al-Li-Sc-Yb alloys contain a finer distribution of Al3(Sc1-x-yLixYby) precipitates at a greater number density and volume fraction, as well as solid-solution strengthening in the Al(Li) matrix, all of which lead to a greater peak strength at ambient-temperature. Because partitioning of Li to the precipitates results in a smaller lattice parameter mismatch with the matrix, a Li addition is detrimental to the elevated temperature strength of Al-Sc alloys, but this effect is mitigated if additions of both Li and Yb are made. A model for threshold stresses at elevated temperature semi-quantitatively captures experimentally-observed trends in threshold stress data in Al-Sc-X alloys. Dislocation dynamics simulations on directly-measured precipitate arrangements lead to a rule for superposition of strength contributions from dissolved solutes, &#945;&#8242;–Al3(Li,Sc,Yb) precipitates, and &#948;&#8242;–Al3Li precipitates. Northwestern University Ph.D. thesis English no NU @ m-krug @ 11430
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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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