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Bcc / B2 phase equilibria and phase transformation from B2 to β’ in refractory Nb-X(Pd, Rh, Ir)-Al
Published online by Cambridge University Press: 18 January 2017
Abstract
For the improvement of oxidation resistance of Nb-based alloys, PdAl-B2 is expected as Al reservoir for Al2O3 surface layer because it is in equilibrium with Nbss (bcc) phase. However, PdAl forms cracks during casting caused by B2 -> β’ transformation. To suppress B2 -> β’ transformation, Rh, Ru and Ir were chosen as additive elements. It is found that bcc / B2 two-phase field in Nb-Pd-Ir-Al system is limited to be small fraction of Ir, while (Pd,Rh)Al-B2 is in equilibrium with bcc solid solution in a wide composition range and addition of Rh prevents occurrence of B2 -> β’ transformation. Composition range of (Pd,Ru)Al-B2 in equilibrium with bcc phase is wider than (Pd,Ir)Al-B2 but narrower than (Pd,Rh)Al-B2. Rh and Ru addition are also beneficial for improving eutectic temperature of Nb-bcc / B2 aluminide two-phase alloys.
- Type
- Articles
- Information
- MRS Advances , Volume 2 , Issue 25: Mechanical Behavior and Failure Mechanisms of Materials , 2017 , pp. 1335 - 1340
- Copyright
- Copyright © Materials Research Society 2017
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Graduate Student