Superplastics properties of an Al-2. 4Mg-1. 8Li-0. 5Sc alloy

Journal Article · Tue Jan 01 00:00:00 EST 1991 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(91)90121-G· OSTI ID:6891810

Bradley, III, E L; Emigh, R A; Morris, Jr, J W ^[1]

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1. Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Engineering Lawrence Berkeley Lab., CA (United States). Center for Advanced Materials

There is a need in the aerospace industry for structural, superplastic aluminum alloys that are formable at strain-rates greater than 10[sup [minus]3] s[sup [minus]1] in order for the economic benefits of superplastic forming to be realized. The standard, structural, superplastic aluminum alloy in the aerospace industry is 7475, which has an optimum forming strain-rate near 10[sup [minus]4] s[sup [minus]1]. Thus, research has been focused on modifying the microstructures of wrought Al-Li alloys such as 2090 and 8090 into superplastically formable (SPF) microstructures with improved properties, but the results have not been completely successful. Superplastic alloys with high strengths have been produced from the Al-Mg-Sc system. These alloys are strengthened by thermomechanical processing which (1) precipitates small, coherent Al[sub 3]Sc particles and (2) increases the dislocation density of the material. The Mg is in solid solution and improves the work hardening capability of these alloys. Because superplastic forming is carried out at relatively high temperatures, recovery processes eliminate the dislocation strengthening resulting from the rolling and overage the precipitates. Thus, additional precipitation strengthening is required to make these alloys attractive for use in aerospace applications. Lithium provides the most promising choice since it forms the ordered coherent precipitate [delta][prime] (Al[sub 3]Li), lowers the density, and increases the stiffness of aluminum alloys. In addition, at low concentrations, Li should be in solution at the SPF temperatures and should have little effect on the superplastic formability of the alloys. This led to research on alloys from the Al-Mg-Li-Sc system. This paper describes the preliminary high-temperature tensile results of an Al-Mg-Li-Sc alloy and relates them to other superplastic Al alloys.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6891810
• Journal Information: Scripta Metallurgica et Materialia; (United States), Vol. 25:3; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
MATERIALS WORKING
MICROSTRUCTURE
PLASTICITY
LITHIUM ALLOYS
MAGNESIUM ALLOYS
DEFORMATION
EXPERIMENTAL DATA
FLOW STRESS
MECHANICAL TESTS
PRECIPITATION HARDENING
SCANDIUM ADDITIONS
ALLOYS
ALUMINIUM ALLOYS
DATA
FABRICATION
HARDENING
INFORMATION
MATERIALS TESTING
MECHANICAL PROPERTIES
NUMERICAL DATA
SCANDIUM ALLOYS
STRESSES
TESTING
360101* - Metals & Alloys- Preparation & Fabrication
360102 - Metals & Alloys- Structure & Phase Studies
360103 - Metals & Alloys- Mechanical Properties