Low-temperature superplasticity in Al alloys processed by equal-channel angular pressing

Ota, Satoshi, Akamatsu, Hiroki, Neishi, Koji, Furukawa, Minoru, Horita, Zenji and Langdon, Terence G. (2002) Low-temperature superplasticity in Al alloys processed by equal-channel angular pressing. Materials Transactions, 43 (10), 2364-2369.

Abstract

Equal-channel angular pressing (ECAP) was applied to achieve grain refinement of Al–3?mass%Mg alloys containing 0.2?mass%Sc, 0.2?mass%Fe or 0.1?mass%Zr. The thermal stability of the fine-grained structures was examined by conducting static annealing experiments. The fine grain sizes produced by ECAP were essentially retained up to a temperature of 523?K for the Fe-containing and Zr-containing alloys and up to a temperature as high as 773?K for the Sc-containing alloy. The three alloys with Sc, Fe and Zr additions were pulled to failure in tension at 523?K corresponding to 0.59Tm, where Tm is the absolute melting point of the alloy, and maximum elongations of ??640%, ??370% and ??390% were obtained at an initial strain rate of 3.3×10?4?s?1, respectively. Such elongations resulted in more than three times or approximately twice the elongation achieved in a binary Al–3%Mg alloy. It is shown that either Fe or Zr may be used as an alternative element in place of Sc to attain low temperature superplasticity. Tensile testing was also conducted on the Sc-containing ternary alloy at a temperature as low as 473?K corresponding to 0.54Tm. A maximum elongation of ??420% was attained at an initial strain rate of 3.3×10?4?s?1. This appears to be the lowest homologous temperature reported to date for superplasticty of Al-based alloys.

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Contributors

Author: Terence G. Langdon

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