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Phase diagram for the Al2O3–HfO2–Y2O3 system

Sergij M. Lakiza ,  Yana Tyschenko ,  Lidiya M. Lopato 

Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Krzizanovsky, Kyiv 38(044), Ukraine

Abstract

The isothermal sections at 1250 and 1650 °С, liquidus surface and solidus surface for the Al2O3–HfO2–Y2O3 phase diagram were constructed for first time. Phase equilibria were established at these temperatures. No ternary compounds and appreciable solid solution regions on the base of components or binary compounds were found in the ternary system. As far as HfO2 interacts with every other phases eutectically, this fact allows to combine in materials the unique properties of HfO2-based T- and F-phases with the properties of other phases of the Al2O3–HfO2–Y2O3 system. The liquidus surface is completed by eight primary crystallization fields. Four four-phase nonvariant eutectic equilibria, one four-phase nonvariant transformation equilibrium and three three-phase nonvariant eutectic equilibria were found in the ternary system. It solidus surface consists of five isothermal fields which correspond to four invariant eutectic equilibria and one invariant transformation equilibrium. The solidus surface includes also six linear surfaces of binary eutectics crystallization end. The highest solidus temperature in the system is 2810 oC – the HfO2 melting point, the lowest – 1755 °C – the ternary eutectic AL+F+Y3A5 melting temperature. The diagram of phase equilibria and the equilibrium alloys crystallization scheme for the Al2O3–HfO2–Y2O3 system were constructed using data on bounding binary systems, liquidus and solidus surfaces.

 

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Related papers

Presentation: Poster at E-MRS Fall Meeting 2009, Symposium I, by Sergij M. Lakiza
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-07 13:41
Revised:   2009-06-07 00:44