Superplasticity in aluminum alloys

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Description

We have characterized in the Al-Mg system the microstructure and mechanical properties of a cold-rolled Al-6Mg-0.3Sc alloy. The alloy exhibited superplasticity at relatively high strain rates (about 10-2 s-1). At a strain rate of 10-2 s-1 there exists a wide temperature range (475-520`C) within which the tensile elongation is over 1000%. There also exists a wide strain rate range (10-3 - 10-1 s-1) within which the tensile elongation is over 500%. The presence of Sc in the alloy results in a uniform distribution of fine coherent Al3SC precipitates which effectively pin grain and subgrain boundaries during static and continuous recrystallization. ... continued below

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13 p.

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Nieh, T. G. December 1, 1997.

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Description

We have characterized in the Al-Mg system the microstructure and mechanical properties of a cold-rolled Al-6Mg-0.3Sc alloy. The alloy exhibited superplasticity at relatively high strain rates (about 10-2 s-1). At a strain rate of 10-2 s-1 there exists a wide temperature range (475-520`C) within which the tensile elongation is over 1000%. There also exists a wide strain rate range (10-3 - 10-1 s-1) within which the tensile elongation is over 500%. The presence of Sc in the alloy results in a uniform distribution of fine coherent Al3SC precipitates which effectively pin grain and subgrain boundaries during static and continuous recrystallization. As a result, the alloy retains its fine grain size (about 7 micron), even after extensive superplastic deformation (>1000%). During deformation, dislocations Mg with a high Schmidt factor slip across subgrains but are trapped by subgrain boundaries, as a result of the strong pining of Al3Sc. This process leads to the conversion of low-angled subgrain boundaries to high-angled grain boundaries and the subsequent grain boundary sliding, which produces superelasticity. A model is proposed to describe grain boundary sliding accommodated by dislocation glide across grains with a uniform distribution of coherent precipitates. The model predictions is consistent with experimental observations.

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13 p.

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OSTI as DE98052197

Other: FDE: PDF; PL:

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  • Other Information: PBD: 1 Dec 1997

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  • Other: DE98052197
  • Report No.: UCRL-ID--129665
  • Grant Number: W-7405-ENG-48
  • DOI: 10.2172/574532 | External Link
  • Office of Scientific & Technical Information Report Number: 574532
  • Archival Resource Key: ark:/67531/metadc698772

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  • December 1, 1997

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  • Aug. 14, 2015, 8:43 a.m.

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  • April 10, 2017, 1:24 p.m.

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Nieh, T. G. Superplasticity in aluminum alloys, report, December 1, 1997; California. (digital.library.unt.edu/ark:/67531/metadc698772/: accessed August 21, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.