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Final Report for Department of Energy Grant No. DE-FG02-02ER45997, "Alloy Design of Nanoscale Precipitation Strengthened Alloys [electronic resource] : Design of a Heat Treatable Aluminum Alloy Useful to 400C".

Published:
Washington, D.C. : United States. Dept. of Energy, 2006.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Additional Creators:
Northwestern University (Evanston, Ill.), United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary:
A creep resistant high temperature Al base alloy made by conventional processing procedures is the subject of this research. The Ni-based superalloys have volume fractions of cubic L1₂ phase precipitates near 50%. This is not attainable with Al base alloys and the approach pursued in this research was to add L1₂ structured precipitates to the Al-Ni eutectic alloy, 2.7 at. % Ni-97.3 at. % Al. The eutectic reaction gives platelets of Al₃Ni (DO₁₁ structure) in an almost pure Al matrix. The Al₃Ni platelets give reinforcement strengthening while the L1₂ precipitates strengthen the Al alloy matrix. Based on prior research and the extensive research reported here modified cubic L1₂ Al₃Zr is a candidate. While cubic Al₃Zr is metastable, the stable phase is tetragonal, only cubic precipitates were observed after 1600 hrs at 425 C and they hardly coarsened at all with time at this temperature. Also addition of Ti retards the cubic to tetragonal transformation; however, a thermodynamically stable precipitate is desired. A very thorough ab initio computational investigation was done on the stability of L1₂ phases of composition, (Al,X)₃(Zr,Ti) and the possible occurrence of tie lines between a stable L1₂ phase and the Al alloy terminal solid solution. Precipitation of cubic (Al{sub (1-x)}Znₓ)₃Zr in Al was predicted by these computations and subsequently observed by experiment (TEM). To test the combined reinforcement-precipitation concept to obtain a creep resistant Al alloy, Zr and Ti were added to the Al-Ni eutectic alloy. Cubic L1₂ precipitates did form. The first and only Al-Ni-Zr-Ti alloy tested for creep gave a steady state creep rate at 375 C of 8 x 10⁻⁹ under 20MPa stress. The goal is to optimize this alloy and add Zn to achieve a thermodynamically stable precipitate.
Report Numbers:
E 1.99:doe/er/45997-5
doe/er/45997-5
Subject(s):
Other Subject(s):
Note:
Published through SciTech Connect.
05/06/2006.
"doe/er/45997-5"
Gautam Ghosh; Morris E. Fine; Dieter Isheim; Semyon Vaynman; Keith Knipling; Jefferson Z. Liu.
Type of Report and Period Covered Note:
Final; 09/01/2002 - 02/28/2006
Funding Information:
FG02-02ER45997
View MARC record | catkey: 14446182