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Novel hexagonal structure and ultrahigh strength of magnesium solid solution in the Mg–Zn–Y system

Published online by Cambridge University Press:  31 January 2011

Akihisa Inoue ,
Yoshihito Kawamura ,
Mitsuhide Matsushita ,
Kentaro Hayashi  and
Junichi Koike
Akihisa Inoue*
Affiliation:
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
Yoshihito Kawamura
Affiliation:
Mechanical Engineering, Kumamoto University, Kumamoto 860–0862, Japan
Mitsuhide Matsushita
Affiliation:
Inoue Superliquid Glass Project, Exploratory Research for Advanced Technology, Japan Science and Technology Corporation, Sendai 982–0807, Japan
Kentaro Hayashi
Affiliation:
Graduate School, Tohoku University, Sendai, Japan
Junichi Koike
Affiliation:
Materials Science and Engineering, Tohoku University, Sendai, Japan
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

A magnesium (Mg) solid solution with a long periodic hexagonal structure was found in a Mg97Zn1Y2 (at.%) alloy in a bulk form prepared by warm extrusion of atomized powders at 573 K. The novel structure has an ABACAB-type six layered packing with lattice parameters of a = 0.322 nm and c = 3 × 0.521 nm. The Mg solid solution has fine grain sizes of 100 to 150 nm and contains 0.78 at.% Zn and 1.82 at.% Y. In addition, cubic Mg24Y5 particles with a size of about 7 nm are dispersed at small volume fractions of less than 10% in the Mg matrix. The specific density (ρ) of the extruded bulk Mg–Zn–Y alloy was 1.84 Mg/m3. The tensile yield strength (σy) and elongation (δ) are 610 MPa and 5%, respectively, at room temperature, and the specific yield strength defined by the ratio of σy to ρ is as high as 3.3 × 105 Nm/kg. High σy values exceeding 400 MPa are also maintained at temperatures up to 473 K. It is noticed that the σy levels are 2.5 to 5 times higher than those for conventional high-strength type Mg-based alloys. The Mg-based alloy also exhibits a high-strain-rate superplasticity with large δ of 700 to 800% at high strain rates of 0.1 to 0.2 s−1 and 623 K. The excellent mechanical properties are due to the combination of the fine grain size, new long periodic hexagonal solid solution containing Y and Zn, and dispersion of fine Mg24Y5 particles. The new Mg-based alloy is expected to be used in many fields.

Type
Articles
Information
Journal of Materials Research , Volume 16 , Issue 7 , July 2001 , pp. 1894 - 1900
Copyright
Copyright © Materials Research Society 2001

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