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Title: Composite precipitates in a commercial Al-Li-Cu-Mg-Zr alloy

Abstract

Composite precipitates with duplex and triplex association of single precipitates commonly found in commercial Al-Li alloys were observed by transmission electron microscopy (TEM) in a re-solution and quenched AA2090 alloy after aging. These novel precipitates were the duplex association of {delta}'(Al{sub 3}Li) and T{sub 1} (Al{sub 2}CuLi) as well as the triplex {delta}'/{beta}'(Al{sub 3}Zr)/T{sub 1} and {delta}'/{beta}'/{theta}'(Al{sub 2}Cu). The reduction of elastic energy associated with composite precipitate formation is suggested as a basic mechanism with plate-like T{sub 1} and {theta}' particles serving as preferential sites for nucleation of either {delta}' or {delta}'/{beta}' spherical particles, which although in much smaller numbers, represent a volume fraction of 10 to 20% of all precipitates.

Authors:
 [1];  [2]
  1. Laboratory for Advanced Materials, State University of the Northern Rio de Janeiro, Av.Alberto Lamego 2000 Horto - Campos CEP 28015-620, Rio de Janeiro (Brazil). E-mail: lucho@uenf.br
  2. Laboratory for Advanced Materials, State University of the Northern Rio de Janeiro, Av.Alberto Lamego 2000 Horto - Campos CEP 28015-620, Rio de Janeiro (Brazil)
Publication Date:
OSTI Identifier:
21003530
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 58; Journal Issue: 2; Other Information: DOI: 10.1016/j.matchar.2006.04.008; PII: S1044-5803(06)00106-9; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AGING; ALUMINIUM ALLOYS; COPPER ALLOYS; ELECTRON DIFFRACTION; LITHIUM ALLOYS; MAGNESIUM ALLOYS; NUCLEATION; PLATES; PRECIPITATION; TRANSMISSION ELECTRON MICROSCOPY; ZIRCONIUM ALLOYS

Citation Formats

Terrones, Luis Augusto H., and Monteiro, Sergio Neves. Composite precipitates in a commercial Al-Li-Cu-Mg-Zr alloy. United States: N. p., 2007. Web. doi:10.1016/j.matchar.2006.04.008.
Terrones, Luis Augusto H., & Monteiro, Sergio Neves. Composite precipitates in a commercial Al-Li-Cu-Mg-Zr alloy. United States. doi:10.1016/j.matchar.2006.04.008.
Terrones, Luis Augusto H., and Monteiro, Sergio Neves. Thu . "Composite precipitates in a commercial Al-Li-Cu-Mg-Zr alloy". United States. doi:10.1016/j.matchar.2006.04.008.
@article{osti_21003530,
title = {Composite precipitates in a commercial Al-Li-Cu-Mg-Zr alloy},
author = {Terrones, Luis Augusto H. and Monteiro, Sergio Neves},
abstractNote = {Composite precipitates with duplex and triplex association of single precipitates commonly found in commercial Al-Li alloys were observed by transmission electron microscopy (TEM) in a re-solution and quenched AA2090 alloy after aging. These novel precipitates were the duplex association of {delta}'(Al{sub 3}Li) and T{sub 1} (Al{sub 2}CuLi) as well as the triplex {delta}'/{beta}'(Al{sub 3}Zr)/T{sub 1} and {delta}'/{beta}'/{theta}'(Al{sub 2}Cu). The reduction of elastic energy associated with composite precipitate formation is suggested as a basic mechanism with plate-like T{sub 1} and {theta}' particles serving as preferential sites for nucleation of either {delta}' or {delta}'/{beta}' spherical particles, which although in much smaller numbers, represent a volume fraction of 10 to 20% of all precipitates.},
doi = {10.1016/j.matchar.2006.04.008},
journal = {Materials Characterization},
number = 2,
volume = 58,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • Trace additions of Zr to Al alloys inhibit recrystallization through the formation of spherical and coherent Al[sub 3]Zr ([beta][prime]) precipitates. Recently, observations have been made of faceted [beta][prime] precipitates in several hot deformed Al alloys, although no systematic experimental study of either the causes of the formation of such precipitates or their orientation relationships with the Al matrix has so far been reported. A detailed examination of the orientation relationships shows that the cube-on-cube orientation relationship existing between spherical, coherent [beta][prime] precipitates and the Al matrix does not hold good for the faceted [beta][prime] particles and that the faceted [beta][prime]more » particles are twin-related with the matrix. It is shown that the twin-related [beta][prime] particles are not incoherent, but bound by large facets fully coherent with the matrix, and that such particles are associated with fairly significant coherency strains. A probable shape of the faceted [beta][prime] is also described.« less
  • The deformation of AA8090 Al-Li-Mg-Cu-Zr alloy at elevated temperature and slow strain rates has been investigated in uniaxial tension. Under suitable conditions, this material exhibited a high strain-rate sensitivity of the flow stress and was superplastic. This superplastic behavior was obtained in material with an initially elongated grain structure combined with a distribution of similarly oriented grains and low-angle grain boundaries that was not conducive to boundary sliding. Observations of the development of microstructure and of the crystallographic preferred orientation indicated that no significant rigid body translation and little rotation of grain interiors occurred up to strains of about 0.4more » and that the probability of relative translation of grain interiors up to strains of at least 1 was low. The changes of structure observed could be accounted for by a combination of grain growth and grain rotation. The consequence of these observations on the grain switching and grain boundary sliding mechanisms generally assumed to operate during superplastic deformation is discussed, with the conclusion that those mechanisms may not be wholly appropriate for explaining high rate sensitivity in this material over the range of strain rates investigated.« less
  • Preliminary indications concerning the applicability of X2095-type alloys for warm temperature applications (125--200 C) are encouraging. The strength capability is clearly demonstrated. Before commitments are made to this alloy system for elevated temperature applications, data need to be gathered on microstructures after long term exposure to the service temperature. Fracture toughness, impact resistance, and creep data are also required to make a complete assessment. The fatigue crack propagation data at 10Hz is also encouraging. More detailed experiments are required to determine the cause for a change in fracture surface morphology compared to room temperature. The fact that these fracture surfacesmore » are so dissimilar, yet the crack propagation rates are nearly identical (in the near threshold region) is perplexing. Additional data are required at lower frequencies and tensile hold times to assess the influence of creep-environment-fatigue interactions, and their impact on component life at these service temperatures.« less
  • Using transmission electron microscopy (TEM) techniques, the phases present in an Al-5.4Cu-1.64Li-0.4Ag-0.4Mg-0.16Zr alloy were identified in the naturally-aged condition and after artificial aging to various times along the aging curve. The effect of prior stretching on the identity of strengthening phases in various aging conditions was also examined. In the naturally aged condition, {delta}{prime} (Al{sub 3}Li) and GP zones were present. Prior stretching discouraged the formation of these GP zones. Upon artificial aging, a reversion occurred in both the stretched and unstretched material that was associated with the dissolution of the GP zones and some of the {delta}{prime}. Longer exposuresmore » to temperature caused the precipitation of more {delta}{prime}, {theta}{prime} (Al{sub 2}Cu), T{sub 1} (Al{sub 2}CuLi) and S{prime} (Al{sub 2}CuMg), and the latter two of these phases remained in the overaged condition. The {delta}{prime} phase precipitated homogeneously in the matrix and heterogeneously on {theta}{prime} and Al{sub 3}Zr. In the unstretched material, the T{sub 1} phase first precipitated on the subgrain boundaries, then in the interior of the subgrains, leaving a precipitate-free zone that decreased in size with longer aging times. The {theta}{prime} in the stretched material produced streaks and spots of lower intensity (in selected area diffraction patterns) than in the unstretched material, for comparable aging times. Overaging of the stretched material, however, resulted in the dissolution of {theta}{prime} and some {delta}{prime} leaving a matrix consisting of T{sub 1}, S{prime} and minor amounts of {delta}{prime}.« less
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