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

Journal of Materials Engineering and Performance (Impact Factor: 0.92). 01/2005; 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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    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. · 0.92 Impact Factor
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    ABSTRACT: The objective of this study was to investigate the feasibility of performing retrogression and reaging (RRA) heat treatments on 2099 aluminum-lithium alloy. The retrogression temperatures were 200-250 °C and retrogression times were 5-60 min. Half of the samples were exposed to a salt fog environment. Interestingly, the samples exposed to salt spray had consistently higher mechanical tensile properties than those which were not exposed.
    Journal of Materials Engineering and Performance 01/2011; 20(6):989-996. · 0.92 Impact Factor
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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; · 0.49 Impact Factor

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