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Effect of precipitate volume fraction on fracture toughness of extruded Mg–Zn alloys

Published online by Cambridge University Press:  31 January 2011

Hidetoshi Somekawa ,
Yoshiaki Osawa ,
Alok Singh  and
Toshiji Mukai
Hidetoshi Somekawa*
Affiliation:
Structural Metals Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
Yoshiaki Osawa
Affiliation:
Structural Metals Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
Alok Singh
Affiliation:
Structural Metals Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
Toshiji Mukai
Affiliation:
Structural Metals Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
*
a)Address all correspondence to this author. e-mail: SOMEKAWA.Hidetoshi@nims.go.jp
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Abstract

Four kinds of extruded Mg–X at.% Zn binary alloys (X = 1.9, 2.4, 3.0, and 3.4) were used to examine the effect of precipitate volume fraction on fracture toughness. All the alloys had fine grain sizes of 1–3 μm and fine sphere-shaped precipitates of 50–60 nm. The volume fraction of precipitates increased with additional zinc content. The results of mechanical property tests showed that the extruded Mg–2.4 at.% Zn alloy exhibited the best balance of strength and fracture toughness. One of the reasons was the different volume fraction of precipitates at the grain boundaries, which was the source of void formation. According to the fracture surface observations and ductile fracture model analysis, the volume fraction of precipitates of 2%–4% was shown to be enough to improve the fracture toughness for the fine-grained magnesium alloys; i.e., higher contents of zinc atoms were not needed to enhance the mechanical properties.

Keywords

ToughnessMg
Type
Articles
Information
Journal of Materials Research , Volume 23 , Issue 4 , April 2008 , pp. 1128 - 1135
Copyright
Copyright © Materials Research Society 2008

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