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Achieving room-temperature superplasticity in an ultrafine-grained Zn-22 % Al alloy

Title
Achieving room-temperature superplasticity in an ultrafine-grained Zn-22 % Al alloy
Author
Kawasaki, Megumi
Keywords
elongation; strain rate sensitivity; superplasticity; ultrafine grained microstructure; Zn-Al alloy
Issue Date
2015-08
Publisher
Institute for Metals Superplasticity Problems, RAS
Citation
Letters on materials, v. 5, NO 3, Page. 269-275
Abstract
The mechanisms of creep and superplasticity occurring in conventional coarse-grained materials are now understood well. However, recent study advances in the production of bulk metals with submicrometer grain sizes which provide the opportunity to demonstrate improved mechanical properties. Thermo-mechanical processing is used in conventional industrial practice to achieve substantial grain refinement in bulk metals whereas the smallest grain sizes achieved in this way are of the order of a few micrometers and generally it is not possible to achieve grain sizes within the submicrometer or nanometer range. In this report, synthesis of an ultrafine-grained Zn-22% Al eutectoid alloy was demonstrated through solutionizing followed by thermo-mechanical processing. Microstructural investigations revealed there are stable equiaxed ultrafine grain sizes of ~0.63 µm with homogeneous distributions of Zn and Al grains. Tensile testing demonstrated the occurrence of excellent room-temperature superplasticity with a maximum elongation of 400% at a strain rate of 1.0×10-3 s-1 where the elongation is one of the highest room-temperature superplastic elongation recorded to date in Zn-22% Al alloy. However, the strain rate sensitivity of superplastic flow was measured as ~0.24 which is lower than the theoretical value of ~0.5 for conventional superplasticity. The present study estimates a threshold stress as one of possible reasons for lowering the strain rate sensitivity of room-temperature superplastic flow in the ultrafine-grained Zn-22% Al alloy.
URI
http://lettersonmaterials.com/en/Readers/Article.aspx?aid=754http://hdl.handle.net/20.500.11754/27166
ISSN
2218-5046; 2410-3535
DOI
10.22226/2410-3535-2015-3-269-275
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > MATERIALS SCIENCE AND ENGINEERING(신소재공학부) > Articles
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