Role of zirconium in the phase formation at the interdendritic zone in nickel-based superalloys
A commercial Alloy 80A and a modified alloy with lower titanium and zirconium contents, e.g. 1.4% and <0.01%, respectively, were subjected to unidirectional solidification followed by a rapid quench in water to preserve the structure at elevated temperatures. The slow solidification results in a coarse dendritic structure with a high enrichment of sulphur (up to 2%), aluminium (up to 4%), titanium (up to 13%) and zirconium in the interdendritic zones. In the commercial Alloy 80A, the zirconium and sulphur present in the interdendritic zone result in a eutectic containing ZrS and NiCrTi-matrix. Excess zirconium forms an NiZr-intermetallic. No TiS is formed in this case. In the absence of zirconium, the titanium enriched in the interdendritic residual melt forms a eutectic of TiS. In both cases the effective solidus temperature corresponding to the composition of the residual melt is 1170°C, compared to 1330 °C, which is the solidus temperature of the bulk material.
KeywordsPolymer Titanium Zirconium Elevated Temperature Bulk Material
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- 1.J. A. Domingue, R. O. Yu and H. D. Flanders, in Conference Proceedings, Cleaveland, OH, 12–13 September 1984 (NASA C1 2337) pp.139–49.Google Scholar
- 2.J. Lacaze, A. Chehaibou and G. Lesoult, Z. Metallkde 80 (1989) 15.Google Scholar
- 3.B. Prinz and G. Rudolph, Mikrochim. Acta (Wien) Suppl. 11 (1985) 275.Google Scholar
- 4.D. Ma and P. R. Sahm, Giessereiforschung 42 (1990) 122.Google Scholar
- 7.B. Marincek, Metall. 31 (1977) 627.Google Scholar