• PDF / 5,058,344 Bytes
• 28 Pages / 593.972 x 792 pts Page_size
• 23 Downloads / 283 Views

DOWNLOAD

REPORT

---

.

INTRODUCTION

THE Al-Fe-O system is of primary importance for the steelmaking industry,[1] ceramic applications[2], and development of refractory materials.[3] The following phases appear in the Al-Fe-O system. Hematite, Fe2O3, and corundum, Al2O3, have limited solubilities in each other forming a miscibility gap. In a narrow temperature interval, a ternary compound with the composition of FeAlO3 appears on the Fe2O3-Al2O3 join. Hercynite, FeAl2O4, has the spinel structure and is mutually soluble with magnetite, Fe3O4. Their solubility is complete above the critical temperature of about 1123.15 K (850 C). Wu¨stite, Fe1xO, can dissolve up to 1 mol pct Al2O3. Liquid slag exists within the

SERGEI A. DECTEROV, Research Professor, is with the Centre de Recherche en Calcul Thermochimique (CRCT), De´p. de Ge´nie Chimique, E´cole Polytechnique, Montre´al, QC, Canada, and also Honorary Professor with the School of Engineering, the University of Queensland, Brisbane, QLD, Australia. Contact e-mail: sergei.decterov@ polymtl.ca DENIS SHISHIN and VIKTORIA PROSTAKOVA, Postdoctoral Research Fellows, and EVGUENI JAK, Professor, are with the School of Engineering, the University of Queensland. Manuscript submitted May 25, 2015. Article published online November 12, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B

FeO-Fe2O3-Al2O3 compositional range. Liquid Al-Fe alloys dissolve up to 1 wt pct oxygen. A number of intermetallic compounds and solutions exist on the Al-Fe side of the system. The lists of the stable phases, models, and notation used in the present study are given in Table I along with the structural data.[4] A thermodynamic ‘‘optimization’’ of the Al-Fe-O system is reported in the present study. In a thermodynamic ‘‘optimization’’ of a system, all available thermodynamic and phase diagram data are evaluated simultaneously in order to obtain one set of model equations for the Gibbs energies of all phases as functions of temperature and composition. From these equations, all of the thermodynamic properties and the phase diagrams can be back-calculated. In this way, all the data are rendered self-consistent and consistent with thermodynamic principles. Thermodynamic property data, such as activity data, can aid in the evaluation of the phase diagram, and phase diagram measurements can be used to deduce thermodynamic properties. Discrepancies in the available data can often be resolved, and interpolations and extrapolations can be made in a thermodynamically correct manner. The described procedure is sometimes referred to as Calphad technique. A small set of model parameters is obtained. This is ideal for computer storage and calculation of properties and phase diagrams. In the present study, all calculations were carried out using the FactSage thermochemical software and databases.[5]

VOLUME 47B, FEBRUARY 2016—397

Table I. Phase

Stable Oxide and Metallic Phases in the Al-Fe-O System

Model

Oxide phases Corundum c-Al2O3 FeAlO3 Spinel Wu¨stite Slag (liquid oxide) Metallic phases Liquid metal fcc bcc Al13Fe4 Al5Fe4