| |
Records |
Links  |
|
Type |
Marquis, Emmanuelle A.; Seidman, David N. |
| |
Publication |
Nanostructural Evolution of Al[sub:3]Sc Precipitates in an Al-Sc-Mg Alloy by Three-Dimensional Atom Probe Microscopy |
Volume |
Journal Article |
Pages |
2004 |
| |
Abstract |
Surface and Interface Analysis |
|
| |
Corporate Author |
Surf. Interface Anal. |
|
Publisher |
36 |
|
Editor |
5-6 |
| |
Summary Language |
559 - 563 |
Series Editor |
atom probe microscopy Mg segregation coherent heterophase interface Gibbsian excess; Al-Sc |
|
Abbreviated Series Title |
The effects of Mg alloying on the precipitation of Al3Sc precipitates were investigated, focusing on nanostructural evolution during isothermal aging at 300C. Three-dimensional atom probe microscopy was performed on samples both in the as-quenched state and after aging for various times. Magnesium tends to segregate at the coherent Al/Al3Sc interface, with a measured value of 1.9 0.5 atom nm-2 for the relative Gibbsian excess of Mg with respect to Al and Sc. This value is constant for all heat treatments, thereby demonstrating that the system is in global thermodynamic equilibrium. This study provides direct experimental evidence for first-principles calculations, which explain morphological changes of Al3Sc precipitates in the presence of Mg observed by high-resolution electron microscopy. Evidence for the presence of Mg atoms in the center of the precipitates is also found, and is discussed in terms of heterogeneous nucleation of the precipitates on MgSc atomic clusters. |
| |
Series Issue |
Marquis, E. A. Sandia Natl Labs, Livermore, CA 94551 USA Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA |
ISSN |
|
|
Medium |
|
| |
Expedition |
|
Notes |
|
|
Call Number |
|
|
Contribution Id |
|
|
Serial |
|
URL |
|
ISBN |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ karnesky @ |
|
659 |
| Permanent link to this record |
| |
|
| |
|
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 |
| Permanent link to this record |
| |
|
| |
|
van Dalen, Marsha E. |
|
Microstructure and Creep Properties of Al-Sc Alloys Micro-alloyed with Lanthanides (Yb or Gd) and Transition Metals (Ti or Zr) |
|
Book Whole |
|
2007 |
|
|
|
|
|
|
|
|
|
289 |
|
Al-Sc |
|
This thesis examines the effects of micro-alloying additions to Al-Sc alloys on the
microstructure, coarsening resistance and creep properties. The overarching goal of this research
is to develop castable, creep-resistant aluminum alloys which can be used at temperatures in
excess of 300°C. Successful high-temperature application of aluminum based alloys offers a
lower cost and lower weight alternative to other materials commonly used at high temperatures,
including titanium- and nickel-based alloys.
To this end, this aims to improve the properties of the Al alloys by adding various
alloying elements in small quantities, on the order of several hundred atomic parts per million, to
aluminum. The thesis begins by focusing on additions of Ti to Al-Sc. Ti is a slow diffuser in Al
[1], and it will be shown that it improves the coarsening kinetics of the precipitate phase at
300°C. Since these alloys are coarsening resistant, it is found that they can be aged and crept at
temperatures of up to 425°C. The properties displayed are similar to those of Al-Sc-Zr alloys
studied previously [2, 3].
The examination of Ti additions is followed by a study of the additions of lanthanide
elements. These elements are of interest since they are known to increase the lattice parameter of
the precipitate phase [4-8], which could potentially lead to improved creep resistance [9].
Initially, binary Al-Yb alloys are studied to obtain some fundamental knowledge of the behavior
of Yb in Al. Subsequent additions of Yb to Al-Sc result in improved creep resistance. A similar
improved creep resistance is observed for additions of Gd to Al-Sc.
Finally, this dissertation concludes with the study of Al-Sc-Yb-Zr alloys. Since the goal
of this research is to obtain a creep-resistant as well as coarsening resistant alloy, both a slow
diffusing element (Zr) and an element which improves the creep resistance (Yb) are added. The
quaternary alloys are found to maintain the creep resistance and coarsening resistance of the Al-
Sc-Yb and Al-Sc-Zr alloys, respectively, which points to opportunities for future research in this
area. |
|
|
|
Northwestern University |
|
Ph.D. thesis |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ karnesky @ |
|
9848 |
| Permanent link to this record |
| |
|
| |
|
Karnesky, Richard A.; Seidman, David N |
|
Criteria for Consistent Steady-State Coarsening |
|
Journal Article |
|
2007 |
|
Scripta Materialia |
|
Scripta Mater. |
|
In Preparation |
|
|
|
|
|
Al-Sc |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ karnesky @ |
|
1912 |
| Permanent link to this record |
| |
|
| |
|
Monachon, C.; Krug, M. E.; Seidman, D. N.; Dunand, D. C. |
|
Chemically and Structurally Complex Nanoscale Core/Double-Shell Nanoscale Precipitates in an Al-Li-Sc-Yb Alloy |
|
Journal Article |
|
2010 |
|
Acta Materialia |
|
|
|
Submitted |
|
|
|
|
|
Al-Sc |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ karnesky @ |
|
10883 |
| Permanent link to this record |
| |
|
| |
|
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 |
| Permanent link to this record |
| |
|
| |
|
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 |
| Permanent link to this record |
| |
|
| |
|
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≤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 |
| Permanent link to this record |
| |
|
| |
|
Knipling, Keith E |
|
Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy Containing Trialuminide Precipitates |
|
Book Whole |
|
2006 |
|
|
|
|
|
|
|
|
|
230 |
|
Al-Zr |
|
This research is toward developing a castable and heat-treatable precipitation-strengthened aluminum alloy exhibiting coarsening- and creep resistance at temperatures exceeding 400°C. Criteria for selecting alloying elements capable of producing such an alloy are established. Those systems forming Al3M trialuminide compounds with a cubic L12 crystal structure are favored, and based on a review of the existing literature, these are assessed in terms of solid-solubility and diffusivity in α-Al (satisfying the need for slow coarsening kinetics), and castability (which is discussed based on the binary phase diagrams). The first Group 3 element, Sc, and the second Group 4 element, Zr, are shown to be most promising.
These expectations are confirmed by an initial study on the Al-Ti system, which demonstrates that conventionally-solidified alloys are not capable of precipitation strengthening. The Al-Zr system, by contrast, exhibits precipitation of nanometer-scale Al3Zr (L12) producing pronounced precipitation hardening when aged at 375, 400, or 425°C. The Al3Zr precipitates are coarsening resistant and have the metastable L12 structure up to 500°C, a result of very sluggish diffusion of Zr in α-Al. Ternary additions of Ti are also investigated, forming Al3(Zr,Ti) (L12) precipitates with a reduced lattice parameter mismatch with α-Al, potentially improving the coarsening resistance.
The composition of Al3(Zr,Ti) precipitates formed at 375 or 425°C are measured directly using 3-D atom-probe tomography. At these temperatures, the Zr:Ti atomic ratio in the precipitates is about 10 and 5, respectively, indicating that most of the available Ti fails to partition to the Al3(Zr,Ti) phase. This is consistent with prior studies on Al-Sc alloys, where the slower-diffusing ternary solute species make up a small fraction of the Al3Sc-based precipitates. Despite the confirmed presence of Ti, Al3(Zr,Ti) precipitates exhibit no improvement in terms of coarsening resistance compared to binary Al3Zr.
Mechanical properties of the Al-Zr and Al-Zr-Ti alloys are investigated utilizing Vickers microhardness and creep. The alloys deformed by creep at 300−400°C exhibit a dislocation climb-controlled threshold stress, ca. 6−12 MPa. The binary Al-Zr and ternary Al-Zr-Ti alloys behave similarly under ambient- and high temperature loading, consistent with the similar microstructures of the two alloys. |
|
|
|
|
|
Ph.D. thesis |
|
Northwestern University |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ keith.knipling @ |
|
1785 |
| Permanent link to this record |
| |
|
| |
|
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 |
| Permanent link to this record |
