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Effect of growth rate on microstructure and microstructure evolution of directionally solidified Nb-Si alloys

Published online by Cambridge University Press:  21 September 2018

Yoshihito Sekito ,
Seiji Miura ,
Kenji Ohkubo ,
Tetsuo Mohri ,
Norihito Sakaguchi ,
Seiichi Watanabe ,
Yoshisato Kimura  and
Yoshinao Mishima
Yoshihito Sekito
Affiliation:
Division of Materials Science and Engineering, Graduate School of Engineering, Hokkaido University
Seiji Miura
Affiliation:
Division of Materials Science and Engineering, Graduate School of Engineering, Hokkaido University
Kenji Ohkubo
Affiliation:
Division of Materials Science and Engineering, Graduate School of Engineering, Hokkaido University
Tetsuo Mohri
Affiliation:
Division of Materials Science and Engineering, Graduate School of Engineering, Hokkaido University
Norihito Sakaguchi
Affiliation:
Center for Advanced Research of Energy Conversion Materials, Hokkaido University
Seiichi Watanabe
Affiliation:
Center for Advanced Research of Energy Conversion Materials, Hokkaido University
Yoshisato Kimura
Affiliation:
Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology
Yoshinao Mishima
Affiliation:
Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology
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Abstract

In the present work, Nb-18.1Si-1.5Zr alloy rods are produced with a growth rate ranging from 1.5 to about 1500 mm/h using the optical floating zone (OFZ) furnace. A part of each specimen is heat-treated at 1650 oC for 100 h. The microstructure was observed using SEM and TEM and analyzed using EPMA and EBSD.

Eutectic-cells are observed in as-grown specimens with a growth rate of 150 mm/h or higher. It is found by EBSD analysis that the solidification direction of Nb is along <113> and that of Nb3Si is along <001], and {112} of Nb and {110) of Nb3Si are parallel. The present crystallographic orientation relationship between Nb and Nb3Si is different from that found in previous reports by several researchers. It was also confirmed that the heat-treated microstructure in the specimen grown by OFZ with a growth rate of 150 mm/h is similar to that in the heattreated specimen prepared by arc-melting.

Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1128: Symposium U – Advanced Intermetallic-Based Alloys for Extreme Environment and Energy Applications , 2008 , 1128-U05-38
Copyright
Copyright © Materials Research Society 2009

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