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Study of The Microstructure and Oxidation of NbSi2 Base Alloys

Published online by Cambridge University Press:  22 February 2011

S.H. Pitman
Affiliation:
Department of Material Science and Engineering, University of Surrey, Guildford, GU2 5XH, United Kingdom
P. Tsakiropoulos
Affiliation:
Department of Material Science and Engineering, University of Surrey, Guildford, GU2 5XH, United Kingdom
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Abstract

The microstructures of arc melted ingots and melt spun ribbons of NbSi2 and NbSi2-(8,20 at%)Cr alloys are discussed. Rapid quenching from the melt refined the grain size of the alloys by two orders of magnitude and suppressed the formation of Nb5Si3 in Zone A of the binary alloy ribbons. In the ternary alloy ingots and ribbons formation of the Nb5Si3 was suppressed, and the C40 NbSi2 and CrSi2 and orthorhombic Nb2Si6Cr3 phases were formed. Zone A was not formed in the ribbons of the ternary alloys. The microhardness of these phases and the oxidation behaviour of the alloys up to 1350°C in air and an Ar atmosphere are discussed. NbSi2 did not form a protective silica layer on oxidation. Instead a mixed oxide scale of silica and α-Nb2O5 formed which cracked during growth of the oxide and hindered protection of the alloy. It is shown that the addition of Cr modifies the oxide to a duplex oxide of SiO2 and Cr2O3 and that the underlying matrix becomes depleted in Cr. Pest oxidation at 750°C was suppressed in Nb-60Si-20Cr.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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References

[1] Nekkanti, R and Dimiduk, D M in Intermetallic Matrix Composites, eds Anton, D.L. et al (Mater. Res. Soc. Proc. 194, 1990) pp. 175182.Google Scholar
[2] Goldschmidt, H J, J. Institute of Metals, 87, 235 (1959).Google Scholar
[3] Priceman, S and Sama, L, in Refractory Metals and Alloys, ed Jaffee, R.I. (Gordon and Breach, New York, 1965), p. 959.Google Scholar
[4] Goldschmidt, H J and Brand, J A, J. Less-Common Metals 3(1), 34 (1961).Google Scholar
[5] Prokoshkin, D A and Vasil’eva, E V, in Alloys of Niobium, ed Samarin, A M, (Israel Program for Scientific Translations, Jerusalem, 1965), p. 100.Google Scholar
[6] Nakamura, M in JIMIS-6 Intermetallic Compounds, ed. Izumi, O, (Japan Institute of Metals, Sendai, 1991), pp.655659.Google Scholar
[7] Shah, D M and Anton, D L, in Structural Intermetallics, eds Darolia, R et al., (TMS, Warrendale, 1993) pp.755764.Google Scholar
[8] Fleischer, R L, in JIMIS-6 Intermetallic Compounds, ed. Izumi, O, (Japan Institute of Metals, Sendai, 1991) pp.157164.Google Scholar
[9] Grabke, H J and Brumm, M in Oxidation of High Temperature Intermetallics, eds Grobstein, T and Doychak, J, (TMS, Warrendale, 1989) pp.245255.Google Scholar
[10] Kieffer, R, Benesovsky, F. and Schroth, H., Metallkunde, Z., 44, 437 (1953).Google Scholar
[11] Rausch, J J, ARF 2981-4, Armour Research Foundation, NSA 15-31171, (1961).Google Scholar