Liquidus and Solidus Surfaces in the Quaternary Fe-Cu-Co-S System. Part I: The Ternary Cu-Co-S System
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INTRODUCTION
THIS study is the continuation of the investigations devoted to phase equilibria of multi-component sulfidemetallic systems using many modern physico-chemical methods of a material investigation. Previously, the authors performed similar detailed analyses of phase equilibria occurring at crystallization of melts of Fe-NiCu,[1] Cu-Ni-S,[2] Fe-Cu-S,[3] and Fe-Ni-S[4] systems, each of the said systems being of the applied relevance for copper and nickel metallurgy. At the initial stage of the study, the available papers devoted to investigation of the discussed system and its boundary subsystems were reviewed. The results of studies of phase equilibria occurring at crystallization of the Cu-S, Co-S, and Cu-Co binary systems melts[5–13] are characterized by a high level of conformity. However, there are only few publications devoted to the study of phase transformations and positions of liquidus and solidus surfaces in the Cu-Co-S ternary system. In particular, Peyronel and Pacilli[14] examined mechanisms of crystallization of components in the Cu-Co-S system limited by the Cu2S1+n-CoS pseudo-binary section. Authors of this work investigated the boundaries of the liquidus miscibility gap area stretched out along the Cu-Co side based on the results of metallographic and X-ray analyses of only four samples. Chang et al.[15] summarized all the information on the ternary system available in the earlier publications, and supplemented the phase transformation scheme with the peritectic transformation occurring in the boundary Co-S system at 1218 K (945 C). Craig et al.[16] studied the system solid phase transformations only, their MARIA O. ILATOVSKAYA, Ph.D. Student, and ROMAN V. STARYKH, Lecturer, are with the St. Petersburg State Polytechnical University, St. Petersburg, Russia. Contact e-mail: [email protected] SVETLANA I. SINYOVA, Engineer, is with the St. Petersburg State Polytechnical University, and also with the Gipronickel Institute, St. Petersburg, Russia. Manuscript submitted November 20, 2012. Article published online September 10, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
nature being discussed based on the isothermal sections of the Cu-Co-S system diagram at 673 K, 773 K, 873 K, 973 K, 1073 K, and 1173 K (400 C, 500 C, 600 C, 700 C, 800 C, and 900 C) plotted by the authors. Our study is focused on the phase transformations taking place at crystallization of the Cu-Co-S ternary system melts, as well as on plotting surfaces of the said system liquidus and solidus using many modern analytical methods: differential thermal analysis (DTA), thermogravimetry (TG), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). A substantial number of analyzed samples and using the technique verified in the earlier works[1–4] ensure completeness and adequacy of the produced data. Information on the location as well as methodically justified choice of the Cu-Co-S liquidus projection is of primary importance for testing and optimization of the copper-cobalt pyrometallurgical processi
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