Temperature and grain size dependence of superplasticity in a Zn?0.3wt.%Al alloy |
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Authors: | Ha Tae Kwon Koo Hyun Woo Chang Young Won |
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Affiliation: | (1) Materials and Processes Research Center, Research Institute of Industrial Science and Technology (RIST), San 32 Hyoja-dong, Nam-gu, 790-600 Pohang, Korea;(2) Department of Materials Science and Engineering, Pohang University of Science and Technology, San 31 Hyoja-dong, Nam-gu, 790-784 Pollang, Korea |
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Abstract: | The superplastic deformation behavior of quasi-single phase Zn-0.3 wt. %Al was investigated. A series of load relaxation and
tensile tests was conducted at various temperatures ranging from RT (20 °C) to 200 °C. The recently proposed internal variable
theory of structural superplasticity was applied. The flow curves obtained from load relaxation tests were shown to consist
of contributions from interface sliding (IS) and accommodating plastic deformation. In the case of quasi-single phase Zn-0.3
wt.% Al alloy with an average agrain size of 1 μm, the IS behavior could be described as a viscous flow process characterized
by a power index of Mg=0.5. A large elongation of about 1400% was obtained at room temperature and the strain rate sensitivity parameter was about
0.4. Although relatively large-grained (10 μm) single phase alloy showed a high value of strain rate sensitivity comparable
to that of fine-grained alloy at very low strain rate range, IS was not expected from the analysis based on the internal variable
theory of structural superplasticity at room temperature. As the temperature increased above 100 °C, however, the contribution
from IS was observed at a very low strain rate range. A high elongation of ∼400% was obtained in a specimen of 10-μm-grain-size
at 200 °C under a strain rate of 2×10−4/sec.
Jointly appointed at Center for Advanced Aerospace Materials (CAAM) |
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Keywords: | superplasticity dilute Zn− Al alloy load relaxation interface sliding accommodation mechanism |
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