Design of multistep aging treatments of 2099 (C458) Al-Li alloy

Journal of Materials Engineering and Performance (Impact Factor: 0.98). 10/2005; 14(5):641-646. DOI: 10.1361/105994905X64594

ABSTRACT Multistep artificial aging treatments coupled with various natural aging times for aluminum lithium 2099 alloy (previously
called C458) are discussed to obtain mechanical tensile properties in the T6 condition that match those in the T861 condition,
having a yield strength in the range of 414–490 MPa (60–71 ksi), an ultimate strength in the range of 496–538 MPa (72–78 ksi),
and 10–13% elongation. Yield and ultimate tensile strengths from 90–100% of the strength of the as-received material (in the
T861 condition) were obtained. The highest tensile strengths were consistently obtained with two-step, low-to-high temperature
artificial aging treatments consisting of a first step at 120 °C (248 °F) for 12–24 h followed by a second step between 165
and 180 °C (329–356 °F) for 48–100 h. These T6-type heat treatments produced average yield and ultimate strengths in the longitudinal
direction in the range of 428–472 MPa (62.1–68.5 ksi) and 487–523 MPa (70.6–75.9 ksi), respectively, as well as lower yield
strength anisotropy when compared with the as-received material in the T861 condition.

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Available from: O. S. Es-Said, Mar 26, 2014
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    • "A representative third-generation Al– Li alloy is the AF/C 458 alloy, which was developed in 1997 and designated as AA 2099 by the Aluminum Association in 2004 [4]. When compared to its predecessor of 2090, 2099 has fewer planar anisotropy, higher transverse ductility, superior stress corrosion cracking resistance , and excellent toughness, and like 2090, it has superb cryogenic properties [5] [6]. "
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    ABSTRACT: The microstructure evolution and composition distribution of as-cast and homogenized 2099 aluminum–lithium (Al–Li) alloy were studied by optical microscopy (OM), differential thermal analysis (DTA), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), area and line scanning, X-ray diffraction (XRD), and Vickers microhardness test methods. The results show that severe dendrite exists in the as-cast alloy. Cu, Zn, Mn, and Mg distribute unevenly from the grain boundary to inside. The low-melting point nonequilibrium eutectic phases dissolve into the matrix during the first-step homogenization, whereas the melting point of residual eutectic phases is elevated. After the second-step homogenization, most of the remaining eutectic phases dissolve into the matrix, except a small amount of Al–Cu–Fe phases. An optimized homogenization process of the 2099 Al–Li alloy is developed (515 °C × 18 h + 525 °C × 16 h), which shows a good agreement with the homogenization kinetic analysis results.
    Rare Metals 02/2013; 33(1). DOI:10.1007/s12598-013-0099-9 · 0.81 Impact Factor
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    ABSTRACT: Delamination fracture has limited the use of lightweight Al-Li alloys. In the present study, electron backscattered diffraction (EBSD) methods were used to characterize crack paths in Al-Li alloy C458 (2099). Secondary delamination cracks in fracture toughness samples showed a pronounced tendency for fracture between grains exhibiting variants of the same deformation texture component. These results were analyzed by EBSD mapping methods and simulated with finite element analyses. Simulation procedures include a description of material anisotropy, local grain orientations, and fracture utilizing crystal plasticity and cohesive zone elements. By comparing the Taylor factors for a combined normal and shear deformation of adjacent grains, it was observed that grain pairs with the largest differences were also those that failed. Examination of matching delamination fracture surface pairs revealed pronounced slip bands in only one of the grains bordering the delamination. These results, along with EBSD studies, plasticity simulations, and Auger electron spectroscopy observations support a hypothesis that delamination fracture occurs due to poor slip accommodation between crystallographically soft and hard grains.
    12th International Conference on Fracture; 07/2009
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    ABSTRACT: A retrogression and reaging (RRA) treatment was performed on 2195 Al-Li Alloy. The exposure times were from 5 to 60min, and the temperatures were from 200 to 250°C. Samples that were exposed to a salt spray test had overall similar mechanical properties as compared to those that were not exposed. The percent elongation, however, was significantly deteriorated due to the salt spray exposure. The mechanical properties of the 2195 samples were compared to those of 2099 samples exposed to similar treatments in an earlier study. Keywordsaluminum lithium alloys–retrogression and reaging–2195 and 2099 alloys
    Journal of Materials Engineering and Performance 01/2011; 20(6):1003-1014. DOI:10.1007/s11665-010-9739-5 · 0.98 Impact Factor
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