Precipitation Behavior and Phase Stability of Intermetallic Phases in Fe-Cr-W-Co Ferritic Alloys

Abstract:

Precipitation behavior of intermetallic phases in ferrite matrix is investigated by transmission electron microscopy (TEM) in Fe-10Cr-1.4W-4.5Co (at%) alloys with and without 0.3at%Si. It is intended to provide basic information for the alloy design of ferritic heat resistant alloys strengthened by intermetallic compounds. In the alloy containing Si, icosahedral quasicrytalline phase (I-phase) is found to precipitate during aging at 873K. It is confirmed that selected area diffraction (SAD) patterns of the precipitates exhibit two-, three- and five-fold symmetry and have diffraction spots in the positions related to the golden section. In the Si-free alloy, the R-phase precipitates instead of I-phase at 873K, and the Laves phase precipitates in both alloys during aging at higher temperature, 973K. The Laves phase formed at 973K transforms to the I-phase in the Si-added alloy but to the R-phase in the Si-free alloy during subsequent aging at 873K. The factors in controlling the phase stability of I-phase, R-phase and Laves phase precipitates in Fe-based alloys are discussed by the atomic size ratio and electron concentration factor (e/a).

• Periodical: Materials Science Forum (Volumes 475-479)
• Pages: 845-848
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.475-479.845
• Online since: January 2005
• Authors: Keisuke Yamamoto, Yoshisato Kimura, Yoshinao Mishima
• Keywords: Ferritic Heat Resistant Steel, Laves Phases, Quasicrystal, R-Phase, TEM

References

[1] H. Cerjak, P. Hofer and B. Schaffernak: ISIJ Int. Vol. 39 (1999), p.874.

[2] F. Abe: Mater. Sci. Eng. A319-321 (2001), p.770.

[3] K. Yamamoto, Y. Kimura and Y. Mishima: ISIJ Int. Vol. 43 (2003), p.1253.

[4] K. Yamamoto, Y. Kimura and Y. Mishima: Mater. Trans. Vol. 45 (2004), p.357.

[5] D. Shechtman, I. Blech, D. Gratias and J. W. Cahn, Phys. Rev. Lett., Vol. 53 (1984), P. (1951).

[6] Y. Komura, W. G. Sly and D. P. Shoemaker: Acta Cryst. Vol. 13 (1960) p.575.

[7] F. Laves, H. Witte: Metallwirschaft 14 (1935), p.645.

[8] F. Laves, H. Witte: Metallwirschaft 15 (1936), p.840.

[9] J. H. Zhu, P.K. Liaw and C. T. Liu: Mater. Sci. Eng. A239-240 (1997), p.260.

[10] T. B. Massalski et al: Binary Alloy Phase Diagrams, second edition (ASM international, 1990).

[11] E. A. Brandes: Smithells Metals Reference Book, sixth edition (Butterworth&Co, 1983, pp.4-26).

[12] Ping Liu, A.H. Stigenberg and J. -O. Nilsson: Acta Mater. Vol. 43 (1995) p.2881.

[13] H. Sidhom and R. Portier: Philos. Mag. Lett. Vol. 59 (1989) p.131.

[14] K. H. Kuo, D. S. Zhou and D. X. Li: Philos. Mag. Lett., Vol. 55 (1987) p.33 Table 2 Atomic size, electron concentration factor (e/a) of alloying element. Table 3 Atomic size ratio (RA/RFe), %A range, corresponding e/a range and structure.