Liquidus and Solidus Surfaces in the Quaternary Fe-Cu-Co-S System: Part II: The Ternary Fe-Cu-Co System
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INTRODUCTION
MULTICOMPONENT metal alloys based on iron, copper, and cobalt show unique strength, electrical, and magnetic features. It is explained by low solubility of iron and cobalt in copper, as well as by efficient copper matrix hardening owing to inclusions of the former metals in the alloy. In general, the said alloys properties are determined by the phase and chemical compositions, as well as by thermal treatment of crystalline alloys. Thus, the Fe-Cu-Co alloys can be considered as composite materials with features such as high ductility, heat conductivity and electrical conductivity of copper, and high strength of iron. Therefore, studying the physical and chemical features of the alloys should be commenced with the examination of the iron-copper-cobalt system phase diagram. Most available publications describe only the thermodynamic parameters of the Fe-Cu-Co system alloys or metastable miscibility gap region.[1–11] For example, Bein et al.[1] identified boundaries of the Fe-Cu-Co diagram phase regions within 1073 K to 1273 K (800 °C to 1000 °C) temperature range by conducting thermodynamic calculations using the cluster variation method. Using the Thermo-Calc AB software (Thermo-Calc Software, Stockholm, Sweden), Bamberger et al.[2] obtained liquidus and solidus temperatures, as well as the limits of the Fe-Cu-Co system metastable miscibility gap. They also demonstrated the good agreement of the calculation results and the experimental data obtained by the electromagnetic levitation (EML). The Fe-Cu-Co alloys separation temperature and miscibility gap limits in the copper-rich corner of the diagram were also defined using EML.[3] MARIA O. ILATOVSKAYA, Ph.D. Student, and ROMAN V. STARYKH, Lecturer, are with 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 April 9, 2014. Article published online October 16, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
Using geometric models and computing methods,[4] thermodynamic parameters of the Fe-Cu-Co system alloys were identified at 1873 K (1600 °C). Curiotto[5] and Egry et al.[6] studied the phase separation in the FeCu-Co system and optimized the ternary diagram using the CALPHAD approach. Wang et al.[7] also used the above method to calculate thermodynamic parameters of the Fe-Cu-Co system phase equilibria. Turchanin et al.[8,9] and Dreval[10] investigated the mixing enthalpy of Fe-Cu-Co melts using the calorimetric method. They calculated liquidus and solidus surfaces, as well as isothermal and vertical sections of the phase diagram and metastable miscibility gap for overcooled alloys. Banda et al.[11] demonstrated advantages of liquidus temperature determination using the differential thermal analysis (DTA) method compared with the EML technique. The measured liquidus temperatures were also compared with predictions from the commercial
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