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Phase Stability of the L12 Compound and Microstructural Changes in Co-(W or Mo)-Ta Ternary Alloys

Published online by Cambridge University Press:  28 August 2018

Hibiki Chinen ,
Toshihiro Omori ,
Katsunari Oikawa ,
Ikuo Ohnuma ,
Ryosuke Kainuma  and
Kiyohito Ishida
Hibiki Chinen
Affiliation:
Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02 Aoba-yama, Sendai 980-8579, Japan
Toshihiro Omori
Affiliation:
Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02 Aoba-yama, Sendai 980-8579, Japan
Katsunari Oikawa
Affiliation:
Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02 Aoba-yama, Sendai 980-8579, Japan
Ikuo Ohnuma
Affiliation:
Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02 Aoba-yama, Sendai 980-8579, Japan
Ryosuke Kainuma
Affiliation:
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan
Kiyohito Ishida
Affiliation:
Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02 Aoba-yama, Sendai 980-8579, Japan
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Abstract

Microstructural investigations of Co-5W-2.5Ta (at.%) and Co-4Mo-4.5Ta (at.%) ternary alloys were conducted. Fine coherent precipitates were observed in these alloys annealed at 800°C, and the crystal structures of precipitates (γ’) and matrix (γ) phase were identified as the L12 and A1 structure, respectively, by transmission electron microscopy. Cellular precipitation with a γ+χ(D019) lamellar structure also proceeded at grain boundaries, and the alloys aged for a longer time only showed the γ+χ two-phase microstructure instead of the γ’ phase. With aging at around 800°C, the peak hardness of these alloys with a γ+γ’ two phase structure was about 580 Hv.

Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1128: Symposium U – Advanced Intermetallic-Based Alloys for Extreme Environment and Energy Applications , 2008 , 1128-U06-08
Copyright
Copyright © Materials Research Society 2009

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