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Formation of 14H-type long period stacking ordered structure in the as-cast and solid solution treated Mg–Gd–Zn–Zr alloys

Published online by Cambridge University Press:  31 January 2011

W.J. Ding ,
Y.J. Wu ,
L.M. Peng ,
X.Q. Zeng ,
G.Y. Yuan  and
D.L. Lin
Y.J. Wu*
Affiliation:
National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China; and The State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
G.Y. Yuan
Affiliation:
National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China; and The State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
D.L. Lin
Affiliation:
National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China; and School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
*
a) Address all correspondence to this author. e-mail: wuyjsjtu@126.com
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Abstract

The coherent fine lamellae consisting of the 2H-Mg and the 14H-type long period stacking ordered (LPSO) structure within α′-Mg matrix have been first observed in an as-cast Mg96.32Gd2.5Zn1Zr0.18 alloy. During subsequent solid solution heat treatment at 698–813 K, in addition to the lamellae within matrix, a novel lamellar X phase (Mg–8.37±1.0Zn–11.32±1.0Gd, at.%) with the 14H-type LPSO structure was transformed from the dendritical β phase, and a corresponding time–temperature–transformation (TTT) diagram was established. The 14H-type LPSO structure existing in Mg–Gd–Zn–Zr alloys derives from two variant means: the formation of LPSO structure within α′-Mg matrix and the transformation of the dendritical β phase to a lamellar X phase with the LPSO structure. The alloy solid solution treated at 773 K for 35 h exhibits higher tensile strength and better elongation than the nonheated alloy because of the lamellar X phase with the 14H-type LPSO structure and the 14H-type LPSO structure within matrix.

Keywords

MgPhase transformationSecond phases
Type
Articles
Information
Journal of Materials Research , Volume 24 , Issue 5 , May 2009 , pp. 1842 - 1854
Copyright
Copyright © Materials Research Society 2009

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