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Diffusion mechanism in the mu phase in Nb-X (X = Ni, Co, Fe) systems

Balam, SSK and Ravi, R and Paul, Aloke (2012) Diffusion mechanism in the mu phase in Nb-X (X = Ni, Co, Fe) systems. In: International Conference on Diffusion in Materials (DIMAT 2011), JUL 03-08, 2011 , ICB Lab, Dijon, FRANCE, pp. 497-501.

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Official URL: http://dx.doi.org/10.4028/www.scientific.net/DDF.3...


Nb is one of the common refractory elements added in Ni, Co and Fe based superalloys. This lead to the formation of brittle topological close packed (tcp) mu phase, which is deleterious to the structure. It mainly grows by interdiffusion and in the present article, the interdiffusion process in different Nb-X (X=Ni, Co, Fe) systems is discussed. The activation energy for interdiffusion is lower in the Co-Nb system (173 kJ/mol) than Fe-Nb system (233 kJ/mol), which is again lower than the value found in the Ni-Nb system (319.7 kJ/mol). The mole fraction of Nb in this phase is less than Fe or Co at stoichiometric compositions in the Nb-Fe (that is Fe7Nb6) and Nb-Co (that is Co7Nb6) systems. On the other hand, the mole fraction of Nb is higher than Ni in the same phase (Ni6Nb2) in Ni-Nb system. However, in all the phases, Nb has lower diffusion rate. Possible diffusion mechanism in this phase is discussed with respect to the crystal structure.

Item Type: Conference Proceedings
Series.: Defect and Diffusion Forum
Additional Information: International Conference on Diffusion in Materials (DIMAT 2011), ICB Lab, Dijon, FRANCE, JUL 03-08, 2011
Keywords: Interdiffusion; mu phase; crystal structure
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 17 Oct 2012 06:00
Last Modified: 17 Oct 2012 06:00
URI: http://eprints.iisc.ac.in/id/eprint/45181

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