NASA/TM-211548, Chen*, P.S. and Bhat, B.N., Time-Temperature-Precipitation Behavior in Al-Li Alloy 2195, George C. Marshall Space Flight Center Marshall Space Flight Center, AL 35812, National Aeronautics and Space Administration Washington, DC 20546-0001, Prepared for the Engineering Directorate, Materials, Processes, and Manufacturing Department * IIT Res, February 2002, pp. 20, Format(s): PDF 17783k |
Transmission electron microscopy was used to study time-temperature-precipitation (TTP) behavior in aluminum-lithium (Al-Li) 2195 alloy. Al-Li 2195 (nominally Al + 4 percent Cu + 1 percent Li + 0.3 percent Ag + 0.3 percent Mg + 0.1 percent Zr) was initially solutionized for 1 hr at 950 F and then stretched 3 percent. Heat treatments were conducted for up to 100 hr at temperatures ranging from 200 to 1,000 F. TTP diagrams were determined for both matrix and subgrain boundaries. Depending upon heat treatment conditions, precipitate phases (such as GP zone, theta double prime, theta prime, theta, delta prime, T1, TB, and T2) were found in the alloy. The TTP diagrams were applied as a guide to avoid T1 precipitation at subgrain boundaries, as part of an effort to improve the alloy's cryogenic fracture toughness (CFT). New understanding of TTP behavior was instrumental in the development of a two-step arctificial aging treatment that significantly enhanced CFT in Al-Li 2195.
| Keywords: | al-cu-li 2195, al-li 2195, time-temperature-precipitation (ttp) diagrams, microstructural characterization, cryogenic fracture toughness (cft), two-step aging treatment, welding parameters |
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| Subjects: | Chemistry and Materials: Metals and Metallic Materials: Aluminum |
| ID Code: | 590 |
| Deposited On: | 02 August 2002 |