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ection II: Phase Diagram Evaluations

C-Cu-Fe-Sb (Carbon-Copper-Iron-Antimony) V. Raghavan

Recently, [2005Voi] determined the liquid miscibility gap and the distribution of Sb and C between the Fe-rich and the Cu-rich liquids at 1200 °C in C-saturated melts of this quaternary system.

Lower Order Systems The mutual solubility between C and Cu is negligible. In the C-Fe system, the C content at saturation in Fe melts increases from 17.1 at.% at 1152 °C to 21 at.% at 1600 °C. The C solubility in Sb melts increases from 0.33 at.% at 1055 °C to 0.94 at.% at 1327 °C. There are a

number of intermediate phases in the Cu-rich part of the Cu-Sb system, none of which is stable at the temperature of interest here (1200 °C). There are no intermediate phases in the Cu-Fe system. A metastable liquid miscibility gap is known in this system. The Fe-Sb phase diagram has two intermediate phases: FeSb1-x (NiAs-type hexagonal) and FeSb2 (marcasite-type orthorhombic). The known phase diagrams for the above systems were given by [Massalski2]. The update on the C-Cu-Fe system by [2002Rag] presented a liquidus projection for the Fe-rich region. The C-Cu-Sb system does not appear to have been investigated. A partial isothermal section at 1200 °C for the C-Fe-Sb system determined by [2005Voi] is shown in Fig. 1.

Fig. 1 C-Fe-Sb partial isothermal section at 1200 °C [2005Voi]

Fig. 3 C-Cu-Fe-Sb tie-lines between C-saturated Fe-rich liquid L1 and Cu-rich liquid L2 at 1200 °C [2005Voi]

Fig. 2 C-Cu-Fe-Sb tie-lines between C-saturated Fe-rich liquid L1 and Cu-rich liquid L2 at 1200 °C [2005Voi]

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Fig. 4 C-Cu-Fe-Sb tie-lines between C-saturated Fe-rich liquid L1 and Cu-rich liquid L2 at 1200 °C [2005Voi]

Journal of Phase Equilibria and Diffusion Vol. 29 No. 6 2008

Phase Diagram Evaluations: Section II

Fig. 5 C-Cu-Fe-Sb partial isothermal section at 1200 °C and at C saturation [2005Voi]

The data on the Cu-Fe-Sb system compiled by [1995Vil] from the early results of [1934Vog] show a miscibility gap between Fe-rich and Cu-rich liquids.

Quaternary Phase Equilibria With starting materials of 99.99% purity, [2005Voi] prepared mixtures with a constant mass ratios of Cu/Fe = 1/3, 1/1, and 3/1, with a graphite rod for achieving C saturation and varying Sb content. The samples were sealed in quartz ampules, melted, and kept at 1200 °C for 12 h before quenching in water. The presence of two clearlyseparated liquids was confirmed by metallography and electron probe microanalysis (EPMA). The composition was determined by combustion infrared spectrometry for carbon and by EPMA and inductively coupled plasma spectrometry (ICP) for the other elements. The measured compositions of the coexisting liquids were listed. The C, Fe, and Sb contents of the Cu-rich liquid were between 0.02-0.08, 3-4, and 2.8-29.8 mass%, respectively. The C, Cu, and Sb contents of the Fe-rich phase were between 3.9-4.0, 4-5, and 0.04-1.5 mass%, respectively. The observed variation in the C and Sb contents of the co-existing Fe-rich and Cu-rich liquids at 1200 °C is shown in Fig