Hostname: page-component-78c5997874-dh8gc Total loading time: 0 Render date: 2024-11-19T11:19:23.369Z Has data issue: false hasContentIssue false
  • English
  • Français

Metastable phase evolution in Al2O3 dispersed nanocrystalline NiCr alloys

Published online by Cambridge University Press:  03 March 2011

Dheepa Srinivasan  and
P.R. Subramanian
Dheepa Srinivasan*
Affiliation:
Materials Research Lab, GE India Technology Center, EPIP Phase-2, Bangalore—560066, India
P.R. Subramanian
Affiliation:
Ceramic and Metallurgy Technologies, GE Global Research, Schenectady, New York 12309
*
a) Address all correspondence to this author. e-mail: [email protected]
Get access

Abstract

The high temperature structural stability of nanograined NiCr alloys reinforced with nanoscale yttria and alumina dispersoids, fabricated by electron beam physical vapor deposition (EBPVD), was examined. The yttria particles coarsened very little and also inhibited grain growth in the matrix successfully, whereas the alumina dispersoids coarsened rapidly and were not as effective in restricting matrix grain growth. A hierarchy of phase transformations took place in the Al2O3 particles present as nano dispersoids in a nanograined NiCr matrix , on annealing. Coarsening of the alumina particles was accompanied by these phase transitions. The phase evolution is attributed to differences in free energies between the metastable and stable phases and a kinetic hierarchy in nucleation, brought about by structural and hence interfacial energy considerations.

Keywords

DispersionsNanoscalePhysical vapor deposition (PVD)
Type
Articles
Information
Journal of Materials Research , Volume 22 , Issue 1 , January 2007 , pp. 68 - 75
Copyright
Copyright © Materials Research Society 2007

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1Whittenberger, J.D.: Elevated temperature compressive steady state deformation and failure in the oxide dispersion strengthened alloy MA 6000E. Metall. Trans. A 15, 1753 (1984).CrossRefGoogle Scholar
2Stephens, J.J. and Nix, W.D.: Constrained cavity growth models of longitudinal creep deformation of oxide dispersion strengthened alloys. Metall. Trans. A 17, 281 (1986).CrossRefGoogle Scholar
3Joos, R. and Artz, E.: Cyclic deformation, hold time creep and thermo-mechanical fatigue of an ODS superalloy. Z. Metallkd. 89, 653 (1998).Google Scholar
4De Mestral, B., Eggeler, G., and Klam, H.J.: On the influence of grain morphology on creep deformation and damage mechanisms in directionally solidified and oxide dispersion strengthened superalloys. Metall. Mater. Trans. A 27, 879 (1996).CrossRefGoogle Scholar
5Oca, C.G., Morris, M.A. Munoz, and Morris, D.G.: High temperature structural coarsening of an ODS FeAl intermetallic. Intermetallics 11, 425 (2003).Google Scholar
6Webster, D.: Strengthening mechanisms in dispersion hardened nichrome. Trans. Am. Soc. Metals 62, 936 (1969).Google Scholar
7Wilcox, B.A. and Clauer, A.H.: The role of grain size and shape in strengthening of dispersion hardened nickel alloys. Acta Metall. 20, 743 (1972).CrossRefGoogle Scholar
8Wilson, F.G., Knott, B.R., and Desforges, C.D.: Preparation and properties of some ODS Fe-Cr-Al alloys. Metall. Trans. A 9, 275 (1978).CrossRefGoogle Scholar
9Schaffer, G.B., Loretto, M.H., Smallman, R.E., and Brooks, J.W.: The stability of the oxide dispersion in Inconel alloy MA 6000. Acta Metall. 37, 2551 (1989).CrossRefGoogle Scholar
10Srinivasan, D. and Subramanian, P.R.: Differential role of nanoscaled oxide dispersoids (Y2O3 vs Al2O3) in the high temperature structural stability of NiCr alloys. Metall. Mater. Trans. A 37, 3455 (2006).CrossRefGoogle Scholar
11Souza Santos, P., Souza Santos, H., and Toledo, T.P.: Standard transition aluminas. Electron microscopy studies. Mat. Res. 3, 104 (2000).CrossRefGoogle Scholar
12Jayaram, V. and Levi, C.G.: The structure of δ-alumina evolved from the melt and the γ→δ transformations. Acta Metall. 37, 569 (1989).CrossRefGoogle Scholar
13Levi, C.G., Jayaram, V., Valencia, J.J., and Mehrabian, R.: Phase selection in electrohydrodynamic atomization of alumina. J. Mater. Res. 3, 969 (1988).CrossRefGoogle Scholar
14Dragoo, A.L. and Diamond, J.J.: Transitions in vapour deposited alumina from 300 °C to 1200 °C. J. Am. Ceram. Soc. 50, 568 (1967).CrossRefGoogle Scholar
15Plummer, M.: The formation of metastable aluminas at high temperatures. J. Appl. Chem. 8, 53 (1958).CrossRefGoogle Scholar
16Rooksby, H.P. and Rooymans, C.J.M.: Formation and structure of delta alumina. Clay Min. Bull. 4, 234 (1961).CrossRefGoogle Scholar
17Frieser, R.G.: Phase changes in thin reactively sputtered alumina films. J. Electrochem. Soc. 113, 357 (1966).CrossRefGoogle Scholar
18Saalfeld, H.: Dehydration of gibbsite and the structure of a tetragonal γ-Al2O3. Clay Min. Bull. 3, 249 (1958).CrossRefGoogle Scholar
19Kubaschewski, O. and Alcock, C.B.: Metallurgical Thermochemistry, 5th ed. (Pergamon Press, Oxford, 1979), p. 378.Google Scholar