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Phase Relation and Microstructure of NbCr2 Laves Intermetallics in Ternary Nb-Cr-X Alloy Systems

Published online by Cambridge University Press:  15 February 2011

M. Yoshida
Affiliation:
Miyagi National College of Technology, Natori, Miyagi Prefecture, 981–12, Japan
T. Takasugi
Affiliation:
T. Takasugi, Institute for Materials Research, Tohoku University, Katahira 2–1–1, Aoba-ku, Sendai, 980–77, Japan
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Abstract

The isothermal phase diagrams of ternary alloy systems Nb-Cr-V and Nb-Cr-Mo are determined by metallography, X-ray diffraction (XRD) and transmission electron microscopy (TEM) equipped with energy dispersive X-ray (EDX). In two alloy systems, the C15 NbCr2 Laves phases are equilibrated directly with bcc solid solution without forming any intermediate phases. Relatively large amount of ternary elements V and Mo are soluble in the C15 NbCr2 Laves phases. It is shown that the C15 Laves phases extend along directions so that V occupies Cr site while Mo occupies Nb site. Also, characteristic structure containing micro twins and stacking faults is observed in the C15 Laves phase alloyed with Mo. Bcc phase has a wider solid solution range in the X(=V and Mo)-rich side than the Nb-rich and Cr-rich sides. A variety of duplex microstructures are observed depending on alloy system and alloy composition.

Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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