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On Mo-9Si-18B Alloys with T2-Moss eutectic microstructure: Mechanical Properties and Protective Silicide Coating

Published online by Cambridge University Press:  11 February 2011

Michiaki Kumagai ,
Kazuhiro Ito  and
Masaharu Yamaguchi
Michiaki Kumagai
Affiliation:
Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606–8501, Japan
Kazuhiro Ito
Affiliation:
Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606–8501, Japan
Masaharu Yamaguchi
Affiliation:
Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606–8501, Japan
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Abstract

Direct access to a T2-Moss eutectic microstructure with a nominal composition of Mo-9Si-18B (at.%) was obtained using an optical floating zone method at a growth rate of less than 5mm/h. The Mo-9Si-18B two-phase alloy has relatively high 0.2% proof stress at 1500°C of about 700 MPa and fracture toughness at room temperature (RT) of ∼11 MPaVm. The (Mo,Nb)-19.5Si-B alloys with (Mo,Nb)ss-T1-T2 three-phase eutectic microstructure have lower yield stress at 1500°C and fracture toughness at RT lower than the Mo-9Si-18B two-phase alloy. The dense short rod-type morphology of Moss in the Mo-9Si-18B alloy may be pulled out of T2 matrix and crack bridging may play a crucial role in toughening. Due to the limited ductility of Mo at RT, its morphology is more important rather than its volume fraction in improving the fracture toughness of multi-phase alloys.

Silicide coating on the Mo-9Si-18B alloys with the T2-Moss two-phase microstructure using a halide-activated pack cementation was also examined. The B-doped Mo5Si3 layer with the D8m structure was formed on the substrate after oxidation at 1500°C for 24 hours. The substrate is the source of B atoms. A steady-state weight gain was observed at 1300–1500°C and their steady-state constants are almost equal to those of MoSi2. The weight loss was saturated in 16–26 cycles at 1500°C. It was about -0.4mg/cm2, suggesting thermal stress resistance of the coated Mo-9Si-18B two-phase alloys is sufficient in the present condition.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 753: Symposium BB – Defect Properties and Related Phenomena in Intermetallic Alloys , 2002 , BB5.26
Copyright
Copyright © Materials Research Society 2003

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References

REFERENCES

1. Schneibel, J.H., Kramer, M. J., Ünal, Ö. and Wright, R.N., Intermetallics 9, 25 (2001).Google Scholar
2. Choe, H., Chen, D., Schneibel, J.H. and Ritchie, R.O., Intermetallics 9, 319 (2001).Google Scholar
3. Nieh, T.G., Wang, J.G and Liu, C.T., Intermetallics 9, 73 (2001).Google Scholar
4. Sakidja, R., Myers, J., Kim, S. and Perepezko, J.H. International Journal of'Refractory Metals & Hard Materials 18, 193 (2000).Google Scholar
5. Mendiratta, M.G., Parthasarathy, T.A. and Dimiduk, D.M., Intermetallics 10, 225 (2002).Google Scholar
6. Parthasarathy, T.A., Mendiratta, M.G. and Dimiduk, D.M., Acta Materialia 50, 1857 (2002).Google Scholar
7. Ito, K., Kumagai, M. and Yamaguchi, M., Intermetallics to be submitted.Google Scholar
8. Yoshimi, K., Nakatani, S., Suda, T., Hanada, S., Habazaki, H., Intermetallics 10, 407 (2002).Google Scholar
9. Meyer, M., Kramer, M. and Akinc, M., Adv. Mater. 8, 85 (1996).Google Scholar
10. Meyer, M.K. and Akinc, M., J. Am. Ceram. Soc. 79, 938 (1996).Google Scholar
11. Ito, K., Murakami, T., Adachi, K. and Yamaguchi, M., Intermetallics to be submitted.Google Scholar
12. “Standard Test Method for Plane-Strain Fracture Toughness of Metallic Materials,” E399–90, Annual book of ASTM Standard, Vol. 03.01, (ASTM, Philadelphia, 1997) pp. 408–438.Google Scholar
13. Suzuki, T., Nomura, N., Yoshimi, K. and Hanada, S., J. Japan Inst. Metals 64, 1082 (2000).Google Scholar
14. Kim, W.Y., Tanaka, H., Kasama, A. and Hanada, S., Intermetallics 9, 827 (2001).Google Scholar
15. Kim, W.Y., Tanaka, H. and Hanada, S., Intermetallics 10, 625 (2002).Google Scholar
16. Vasudevan, A.K. and Petrovic, J.J., Mater. Sci. Eng. A155, 1 (1992).Google Scholar