Design of Multistep Aging Treatments of 2099 (C458) Al-Li Alloy

Journal of Materials Engineering and Performance (Impact Factor: 1). 10/2005; 14(5):641-646. DOI: 10.1361/105994905X64594


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.

Download full-text


Available from: O. S. Es-Said, Mar 26, 2014
  • Source
    • "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]. "
    [Show abstract] [Hide abstract]
    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 · 1.01 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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
  • [Show abstract] [Hide abstract]
    ABSTRACT: The anodizing behavior of a lithium-containing aluminum alloy (AA 2099-T8) in an environmentally friendly electrolyte, namely tartaric–sulfuric acid (TSA), has been examined under potentiodynamic and potentiostatic conditions. Specifically, the dependence of the anodic film morphology and composition on the anodizing voltage was investigated. It is revealed that porous anodic films with well-defined cells were formed at relatively low voltages while porous anodic films with pores of increased dimensions and lateral porosity were formed at increased voltages. In addition, it is indicated that copper in the alloy matrix can be occluded in the anodic film material as copper-rich nanoparticles or it can be oxidized and incorporated into the film material as copper ions, depending on the anodizing voltage. In the latter case, the process is accompanied by oxygen gas generation within the film material, resulting in the lateral porosity in the anodic film. Further, the structures of the copper-rich nanoparticles have been determined and the mechanism of the formation of such nanoparticles has been discussed.
    01/2011; 158(2):C17-C22. DOI:10.1149/1.3523262
Show more