Phase relations in the mischmetall-cobalt system

Velu, E. M. T. ; Subbarao, E. C. ; Gupta, H. O. ; Gupta, K. P. ; Kaul, S. N. ; Majumdar, A. K. ; Mittal, R. C. ; Padmavathi Sankar, T. A. ; Sarkar, G. ; Satyanarayana, M. V. ; Shankaraprasad, K. ; Subramanyam, J. (1980) Phase relations in the mischmetall-cobalt system Journal of the Less Common Metals, 71 (2). pp. 219-234. ISSN 0022-5088

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While phase relations in binary systems of pure rare earths with cobalt have been studied extensively, only limited information is available on the MM-Co system, where the mischmetall (MM) contains cerium, lanthanum, neodymium and praseodymium as primary constituents. In the mischmetallcobalt system, six phases MMCo3, MM2Co7, MM5Co19, MMCo5, MM2Co17 and β-Co were identified in the composition range 55-84 wt.% Co. The MMCo3, MM2Co7 and MM5Co19 phases have very similar X-ray patterns and hence they were identified by electron probe microanalysis and thermomagnetic analysis. The MM2Co7 phase exists in both hexagonal and rhombohedral modifications. Of the various phases, only the MMCo5 phase has an observable homogeneity region extending over 2 wt.% Co at 900 °C. The MMCo5 phase is unstable at temperatures below 700°C and the addition of iron increases its instability, leading for example to a nearly complete disappearance in a sample with 12 wt.% Fe in 30 days at 700 °C. The decomposition products of MMCo5 occur at grain boundaries and inside the MMCo5 grains of alloys with low iron contents but they occur as separate grains in alloys with high iron contents.

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ID Code:30070
Deposited On:23 Dec 2010 03:20
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