Experimental Determination And Thermodynamic Calculation Of Phase Equilibria In The Fe-Co-(Nb,Zr) Systems

Fe-Co base alloys are widely used as soft magnetic materials and ultrahigh-temperature alloys in the filed of chemistry and chemical engineering, energy, aviation and medical due to their good soft magnetism, good anti-oxidatin and corronsion resistance, excellent mechanical properties and good biological compatibility. Because the CALPHAD technology has the important application in the designing of metallic alloys, it is necessary to investigate the phase diagrams and thermodynamic properties of the involved systems.In the present work, the experimental determination and thermodynamic assessment in the phase equilibria of the Co-Zr binary system and Fe-Co-X (X: Nb, Zr) two ternary systems were carried out. Major research contents are listed as follows:(1) The phase equilibira of the Co-Zr binary system from 500℃to 1350℃have been experimentally determined in the whole compositional range and the phase diagram in the Co-Zr binary system have been modified.(2) The phase equilibria of the Fe-Co-Zr ternary system at 1300℃, 1200℃, and 1100℃have been experimentally determined for the first time, and the experimental information of the reported Fe-Co-Zr ternary system at 1000℃have been modified.(3) The phase equilibria of the Fe-Co-Nb ternary system at 1300℃, 1200℃, 1100℃, 800℃and 700℃have been experimentally determined for the first time, and the experimental information of the reported Fe-Co-Nb ternary system at 1000℃and 900℃have been modified.(4) On the basis of experimental data obtained by this work and previous reports, the phase equilibria of the Co-Zr binary system, Fe-Co-Zr and Fe-Co-Nb two ternary systems have been calculated and optimized. The calculated results are in good agreements with the experimental data.(5) The compositions of the Ni_57.4Nb_26.97-xTi_15.63Zr_x,Co_yNi_57.4-yNb_23.97Ti_15.63Zr₃,Fe_xNi_57.4-xNb_23.97Ti_15.63Zr₃,Fe_zCo_zNi_57.4-2zNb_23.97Ti_15.63Zr₃ amorphous alloys have been designed based on the thermodynamic parameters obtained by this study, and the application of the CALPHAD technology in the designing of amorphous alloy has been studied in the present work.The obtained results in this work can be applied to establish the thermodynamic database of Fe-based amorphous alloys. In addition, the results in this work can provide important theoretical guidance on designing high performance Fe-based amorphous alloys and ultrahigh-temperature alloys.