Thermodynamic Optimization And Calculation Of Phase Equilibria In The Co-Mn-X (X: Ta, Pt, B, Dy, Pr) Ternary Systems

The Co-Mn based alloys have widely been used as magnetic recording materials, shape memory alloys,magnetic amorphous materials and Heusler alloy due to their excellent magnetism.In order to improve the alloy properties,optimize alloy compositions and processing,it is necessary to investigate the phase diagrams and thermodynamic data in the Co-Mn based systems.In this paper,the experimental investigation and thermodynamic calculation of the phase equilibria in the Co-Mn-X(X:Ta,Pt,B,Dy,Pr) systems were carried out on as follows:(1) Thermodynamic descriptions of the Mn-X(X:Dy,Pr,Pt,Ta) four binary systems were firstly optimized by using the available experimental information.The calculated phase diagrams and thermodynamic properties were in good agreement with the experimental data.(2) The phase equilibria in the Co-rich corner of the Co-Mn-Ta system at 800℃, 900℃,1000℃,1100℃,1200℃and 1300℃were experimentally determined by means of optical microscopy(OM),electron probe microanalysis(EPMA) and X-ray diffraction(XRD) on equilibrated ternary alloys.On the basis of the experimental phase equilibria data of this tenary system obtained by this work,the phase equilibria of the Co-Mn-Ta ternary system were optimized.A set of self-consistent,reasonable and reliable thermodynamic parameters was obtained.The calculated results of the Co-Mn-Ta ternary system were in good agreements with the experimental data.(3) The phase equilibria in the Co-rich corner of the Co-Mn-Pt system at 700℃were experimentally determined by means of diffusion couples and electron probe microanalysis(EPMA).On the basis of the experimental phase equilibria of the tenary system obtained by this work,the partial phase equilibria of the Co-Mn-Pt ternary system were calculated.(4) On the basis of the optimized parameters about the binary subsystems and the experimental data of the Co-Mn-X(X:B,Dy,Pr) ternary systems in the literature and this study,the phase equilibria of these ternary systems were calculated.The phase equilibria of the Co-Mn-X(X:B,Dy,Pr) ternary systems were extrapolated.The resultant thermodynamic parameters in this study can be applied to build the thermodynamic database of high properties Co-Mn based alloy and offer a reliable basis for alloys design of the Co-Mn based alloy.