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Title: Effects of Li content on precipitation in Al-Cu-(Li)-Mg-Ag-Zr alloys

Abstract

Although much attention has been paid to Al-Cu-Li-Mg-Ag-Zr alloys, there are sparse reports about the influence of Li on precipitation in these alloys. The aim of the present study is to determine the effects of Li on modifying precipitation in a baseline aluminum alloy 2195 and the accompanying variants with 0--1.6 wt.% Li.

Authors:
;  [1]
  1. Central South Univ. of Technology, Changsha (China). Dept. of Materials Science and Engineering
Publication Date:
OSTI Identifier:
603857
Resource Type:
Journal Article
Resource Relation:
Journal Name: Scripta Materialia; Journal Volume: 38; Journal Issue: 3; Other Information: PBD: 6 Jan 1998
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM BASE ALLOYS; MICROSTRUCTURE; LITHIUM ADDITIONS; METALLURGICAL EFFECTS; COPPER ALLOYS; MAGNESIUM ADDITIONS; SILVER ADDITIONS; ZIRCONIUM ADDITIONS; PRECIPITATION

Citation Formats

Huang, B.P., and Zheng, Z.Q. Effects of Li content on precipitation in Al-Cu-(Li)-Mg-Ag-Zr alloys. United States: N. p., 1998. Web. doi:10.1016/S1359-6462(97)00503-4.
Huang, B.P., & Zheng, Z.Q. Effects of Li content on precipitation in Al-Cu-(Li)-Mg-Ag-Zr alloys. United States. doi:10.1016/S1359-6462(97)00503-4.
Huang, B.P., and Zheng, Z.Q. Tue . "Effects of Li content on precipitation in Al-Cu-(Li)-Mg-Ag-Zr alloys". United States. doi:10.1016/S1359-6462(97)00503-4.
@article{osti_603857,
title = {Effects of Li content on precipitation in Al-Cu-(Li)-Mg-Ag-Zr alloys},
author = {Huang, B.P. and Zheng, Z.Q.},
abstractNote = {Although much attention has been paid to Al-Cu-Li-Mg-Ag-Zr alloys, there are sparse reports about the influence of Li on precipitation in these alloys. The aim of the present study is to determine the effects of Li on modifying precipitation in a baseline aluminum alloy 2195 and the accompanying variants with 0--1.6 wt.% Li.},
doi = {10.1016/S1359-6462(97)00503-4},
journal = {Scripta Materialia},
number = 3,
volume = 38,
place = {United States},
year = {Tue Jan 06 00:00:00 EST 1998},
month = {Tue Jan 06 00:00:00 EST 1998}
}
  • The independent and combined roles of trace Mg and Ag additions in properties and precipitation of Al-Cu-Li-(Mg)-(Ag)-Zr-Ti alloys were studied. The independent roles of Mg additions are to promote the T{sub 1} precipitation, decrease activation energy for the growth of {theta}{prime} plates and reduce lengthening rates of T{sub 1} and {theta}{prime} plates. The independent roles of Ag additions are to retard GP-zone formation, stimulate the T{sub 1} precipitation and enhance the lengthening rates of T{sub 1} and {theta}{prime} plates. The combined additions of Mg and Ag augment and accelerate the nucleation of T{sub 1} phases. The potent role of independentmore » Mg additions in promoting the precipitation of {theta}{prime} is still effective in the presence of Ag, but it is weakened due to the strong interaction of Mg with Ag. The role of Ag as a stimulus in the lengthening of {theta}{prime} plates is diminished in the presence of Mg additions. The growth of T{sub 1} is controlled by Cu solute diffusion along dislocations regardless of alloy contents of Mg and Ag. The growth of {theta}{prime} plates in the Ag-free alloy is controlled by vacancy-assisted diffusion of Cu.« less
  • The natural aging response of Al-Cu-Li alloys containing trace additions of Mg and Ag was examined as a function of the Li level while the copper level was maintained between 5.0 and 6.5 wt%. A peak in strength was observed at a Li level of {approximately}1.3 wt% with the naturally aged strengths (yield strength = 435 MPa; ultimate tensile strength = 580 MPa) being competitive with those of several high-strength aluminum alloys in the artificially peak-aged condition. The microstructure in the naturally aged condition was characterized using transmission electron microscopy techniques; phases present were identified by selected area diffraction, andmore » dislocation morphology (helices vs loops) was examined by two-beam bright field imaging. Observations were correlated with the measured properties and the peak in strength at {approximately} 1.3 wt% Li is explained on the basis of these microstructural observations.« less
  • Aluminum-lithium alloys that have been hot worked generally suffer from an anisotropy of mechanical properties, both through thickness (surface to centerline) and in plane (from longitudinal to 45[degree] to transverse). Although such anisotropy is present in all tempers, it is more pronounced in the commercially-important, high strength, artificially aged conditions. Yield strength differences between the longitudinal and long transverse orientations ([Delta]YS) of up to 240 MPa for Al-Cu-Li alloy 2090 have been reported. Since minimum properties in all orientations must be considered in applications design, mechanical property anisotropy can limit the use of an alloy. To investigate the role compositionmore » plays in the development of mechanical property anisotropy, the authors have examined a range of compositions in the Weldalite[reg sign] 049 alloy family as well as certain model alloys. This novel approach is in contrast to most attempts to reduce anisotropy which have been based on established alloys of relatively narrow composition ranges. In the present study, a baseline aluminum alloy 2195 (4.0 Cu-0.95 Li-0.4 Ag-0.4 Mg-0.14 Zr, in wt.%) with accompanying experimental variants containing 0 to 1.4% Li and 0.4 and 1.2% Mg, were evaluated for tensile property anisotropy, fracture toughness, and microstructure.« less
  • It has been found that the tensile ductility of some Al-Li alloys increases significantly with decreasing temperature. Although this inverse temperature dependence has often been observed in some non-Li-containing Al alloys, such as Al 2219, the magnitude of improvement in tensile ductility is generally much higher in Li-containing Al alloys. Several hypothetical mechanisms have been proposed to explain the increase in tensile ductility at cryogenic temperatures for Al-Li alloys. At present, the studies on the cryogenic mechanical properties o Li-containing Al alloys are largely limited to ingot-melted alloys, and the data are not readily available for powder metallurgy (PM) processedmore » Al-Li alloys. The refined microstructure of PM processed Al-Li alloys would minimize the extrinsic delamination effects on the tensile properties and, as a result, these may serve as better materials for studying the mechanism(s) for the improved cryogenic tensile properties in Al-Li alloys. The objective of the present study, therefore, was to examine the tensile properties of rapidly solidified (RS)/PM processed Al-Li alloys and to identify the mechanism of the increase in tensile ductility at cryogenic temperatures.« less
  • 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