Using high-pressure torsion to achieve superplasticity in an AZ91 magnesium alloy

Figueiredo, Roberto B. and Langdon, Terence G. (2020) Using high-pressure torsion to achieve superplasticity in an AZ91 magnesium alloy. Metals, 10 (5), 1-10, [681]. (doi:10.3390/met10050681).

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Abstract

An AZ91 magnesium alloy (Mg-9%, Al-1% Zn) was processed by high-pressure torsion (HPT) after solution-heat treatment. Tensile tests were carried out at 423, 523, and 623 K in the strain rate range of 10 ⁻⁵ −10 ⁻¹ s ⁻¹ to evaluate the occurrence of superplasticity. Results showed that HPT processing refined the grain structure in the alloy, and grain sizes smaller than 10 µm were retained up to 623 K. Superplastic elongations were observed at low strain rates at 423 K and at all strain rates at 523 K. An examination of the experiment data showed good agreement with the theoretical prediction for grain-boundary sliding, the rate-controlling mechanism for superplasticity. Elongations in the range of 300–400% were observed at 623 K, attributed to a combination of grain-boundary-sliding and dislocation-climb mechanisms.

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Accepted/In Press date: 19 May 2020

Published date: 22 May 2020

Additional Information: Funding Information: Funding: The authors acknowledge support from FAPEMIG, CNPq, and the European Research Council under ERC grant agreement no. 267464-SPDMETALS. Publisher Copyright: © 2020 by the authors.

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