Experimental Study And Thermodynamic Calculation Of Phase Equilibria Of Nd/Ce-Y-Fe And Dy/Ho-Mn Alloys

With the development of rare earth magnetic materials,it is of great significance to use high-abundant rare earth metals such as La,Ce and Y to reduce the costs of magnets.Phase diagrams of the RE-Y-Fe alloys are beneficial to explore the development of nevol magnets.On the other hand,RE-Mn-based compounds show exhibit excellent magnetic properties due to their unique crystal structure.Phase diagrams of RE-Mn-based alloy systems are necessary to understand the relationship of their crystal structures and physic properties.In this work,phase equilibria,phase transition and solidification microstructure of the RE-Fe and RE-Mn based alloys were investigated through both experimental investigation and thermodynamic calculation.The results were obtained as follows:(1)The phase diagram of the Nd-Y binary system was investigated experimentally by DSC and SEM/EDS.The Nd-Y binary system was thermodynamically calculated using the CALPHAD method.The phase transformation and solidification behavior of Nd-Y-Fe ternary alloys prepared by arc melting were analyzed.Based on the thermodynamic parameters of the Fe-Nd and Fe-Y binary systems performed in our previous work,the vertical section and liquid projection of the Nd-Y-Fe ternary system were calculated.The non-equilibrium solidification paths of the Nd-Y-Fe ternary alloys were calculated by Scheil module.The calculation results are well consistent with the experimental results.(2)The phase transformation of Ce-Y binary alloys were measured experimentally by DSC and SEM/EDS.A set of reasonable thermodynamic parameters was obtained using the CALPHAD method.The phase transformation and solidification behavior of Ce-Y-Fe alloys were analyzed.Thermodynamic description of the Ce-Y-Fe system was established using the CALPHAD method.The liquid projection and vertical section was calculated.The non-equilibrium solidification paths of key alloys were calculated using the Scheil model.The calculated results can reasonably explain the solidification behavior of the alloys.(3)Based on the evaluation of the experimental data reported in the literature,phase diagrams of the Dy-Mn and Ho-Mn binary systems were investigated by DSC and SEM/EDS.using the CALPHAD method,phase diagrams and thermodynamic properties of the Dy-Mn and Ho-Mn binary systems were calculated.The reliable thermodynamic parameters of the Dy-Mn and Ho-Mn binary systems were obtained finally.