TY - JOUR
T1 - Creep properties and precipitate evolution in Al-Li alloys microalloyed with Sc and Yb
AU - Krug, Matthew E.
AU - Seidman, David N.
AU - Dunand, David C.
N1 - Funding Information:
This research is supported by the US Department of Energy, Office of Basic Energy Sciences (Dr. John Vetrano, monitor) through grant DE-FG02-98ER45721 . The LEAP tomograph was purchased with funding from the NSF-MRI (Grant DMR-0420532 ) and ONR-DURIP (Grant N00014-0400798 , Dr. Julie Christodoulou, grant officer) programs. Dr. Sung-Il Baik (Northwestern University) is thanked for assistance in acquiring TEM images, and Dr. Zugang Mao (Northwestern University) is thanked for communicating the results of first-principles calculations. Dr. C. Booth-Morrison (Rolls-Royce Canada, Montreal, Canada) is thanked for many useful discussions. Dr. J. A. Scott (Science and Technology Policy Institute, Washington, DC) is thanked for his assistance in performing creep experiments. The authors are grateful to Dr. R.A. Karnesky (Sandia National Lab, Livermore, CA) and Dr. M.E. van Dalen (Momentive Performance Materials, Richmond Heights, OH) for access to prior creep data for Al–Sc–X alloys. We also gratefully acknowledge the Initiative for Sustainability and Energy at Northwestern (ISEN) for grants to upgrade the capabilities of the Northwestern University Center for Atom-Probe Tomography (NUCAPT).
PY - 2012/7/30
Y1 - 2012/7/30
N2 - A dilute Al-Sc alloy (Al-0.12 Sc, at.%, Al-Sc), its counterpart with a Li addition (Al-2.9 Li-0.11 Sc, at.%, Al-Li-Sc), as well as a quaternary alloy (Al-5.53 Li-0.048 Sc-0.009 Yb, at.%, Al-Li-Sc-Yb) were isothermally aged at 325°C, and in some cases isochronally aged to 450°C. As the α'-Al3(Li,Sc) and Al3(Li,Sc,Yb) precipitates, with L12 structure, coarsen in the two Li-containing alloys, their Li and Yb concentrations decrease and their Sc concentration increases. A significant interfacial excess of Li also segregates at the α-Al matrix/α'-Al3Sc(Li,Sc,Yb) precipitate interface: 5.99±0.05atomsnm-2 in Al-Li-Sc and 13.2±0.4atomsnm-2 in Al-Li-Sc-Yb after aging isochronally to 450°C. During compression creep at 300°C, the aged alloys exhibit threshold stresses between 8 and 22MPa. A recent threshold stress model based on elastic interactions between dislocations and precipitates predicts correctly that Li additions in the Al-Li-Sc alloy reduce the threshold stress, while Yb in the Al-Li-Sc-Yb alloy increases it. The model is also in agreement with the threshold stresses of all Al-Sc-X alloys published to date.
AB - A dilute Al-Sc alloy (Al-0.12 Sc, at.%, Al-Sc), its counterpart with a Li addition (Al-2.9 Li-0.11 Sc, at.%, Al-Li-Sc), as well as a quaternary alloy (Al-5.53 Li-0.048 Sc-0.009 Yb, at.%, Al-Li-Sc-Yb) were isothermally aged at 325°C, and in some cases isochronally aged to 450°C. As the α'-Al3(Li,Sc) and Al3(Li,Sc,Yb) precipitates, with L12 structure, coarsen in the two Li-containing alloys, their Li and Yb concentrations decrease and their Sc concentration increases. A significant interfacial excess of Li also segregates at the α-Al matrix/α'-Al3Sc(Li,Sc,Yb) precipitate interface: 5.99±0.05atomsnm-2 in Al-Li-Sc and 13.2±0.4atomsnm-2 in Al-Li-Sc-Yb after aging isochronally to 450°C. During compression creep at 300°C, the aged alloys exhibit threshold stresses between 8 and 22MPa. A recent threshold stress model based on elastic interactions between dislocations and precipitates predicts correctly that Li additions in the Al-Li-Sc alloy reduce the threshold stress, while Yb in the Al-Li-Sc-Yb alloy increases it. The model is also in agreement with the threshold stresses of all Al-Sc-X alloys published to date.
KW - Atom probe tomography
KW - Lattice parameter mismatch
KW - Mechanical properties (high-temperature deformation)
KW - Rare-earth
KW - Threshold stress
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U2 - 10.1016/j.msea.2012.04.075
DO - 10.1016/j.msea.2012.04.075
M3 - Article
AN - SCOPUS:84861478401
SN - 0921-5093
VL - 550
SP - 300
EP - 311
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
ER -