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In-situ observation of Nb/Nb5Si3 two-phase alloys during bending at various temperatures

Published online by Cambridge University Press:  04 February 2011

Seiji Miura
Affiliation:
Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo 060-8628, Hokkaido, Japan.
Yukiyoshi Tsutsumi*
Affiliation:
Now with KOBELCO Construction Machinery Co., Ltd.
Tetsuo Mohri
Affiliation:
Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo 060-8628, Hokkaido, Japan.
*
*Graduate Student, Graduate School of Engineering, Hokkaido University
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Abstract

In order to understand the deformation and fracture behavior of Nb-Si alloys, in-situ observation was conducted during bending of small specimens at room and high temperatures. Nb-Si alloy ingots containing 18.1 at.%Si, 1.5 at.%Zr and 100 ppmMg were prepared by arc melting, followed by uni-axial solidification in an optical floating zone apparatus and a heat-treatment to obtain Nb/Nb5Si3 two-phase microstructure. Chevron-notched specimens with a dimension of 1x2x10mm were used for in-situ observation of bending tests under a confocal laser scanning microscope (CLSM) at room temperature and at 1140 °C. At room temperature the Nb-Si alloy shows a fracture toughness of 8 MPa m1/2 and the crack propagation velocity seems to be not uniform, presumably due to the ductile Nb. At 1140 °C the toughness of the alloy was about 20 MPa m1/2 and slower plastic deformation prior to the cracking was observed. The SEM observation of crack surfaces revealed that plastic deformation of Nb enhances the toughness of the alloy.

Type
Research Article
Copyright
Copyright © Materials Research Society 2011

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References

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