Thermodynamic Calculation,solidification Microstructure And Magnetic Properties Of The Nd-Ce-Fe-B Alloys

Nd-Fe-B permanent magnets are widely used in aerospace,automobile,wind power and other fields due to their excellent magnetic properties.Phase diagram is an important prerequisite for material design.The relationships among composition,crystal structure and phase transition of RE-Nd-Fe-B magnetic alloys are obtained from their phase diagram and thermodynamic properties.In this work,phase equilibria,solidification microstructure and magnetic properties of Nd-Ce-Fe-B alloys were studied by experimental investigations and thermodynamic calculations.(1)Based on the evaluation of the binary systems(Nd-B,Ce-B,Fe-B,Fe-Nd,Fe-Ce,Nd-Ce)and the ternary systems(Ce-Fe-B,Nd-Fe-B,Ce-Nd-Fe and Ce-Nd-B),thermodynamic database of the Nd-Ce-Fe-B system were developed using the CALPHAD method.The calculated results are in agreement with the literatre data.(2)According to the phase equilibira,the compistions of Nd-Ce-Fe-B alloy samples were designed and prepared by acr melting method.Using the electronic microprobe(EPMA)and X-ray diffraction(XRD)and differential thermal analysis(DSC),phase composition,microstructure,phase transition and solidification process of Nd-Ce-Fe-B alloya were studied.Using thermodynamic calculation with Scheil solidification model,solidification process of Nd-Ce-Fe-B alloy samples was simulated.The calculated results are consistent with the experimental results.(3)Six ribbons(Nd0.8Ce0.2)22Fe72B6,(Nd0.8Ce0.2)12Fe82B6,(Nd0.6Ce0.4)22Fe72B6,(Nd0.6Ce0.4)22Fe82B6,(Nd0.9Ce0.1)16Fe78B6 and(Nd0.7Ce0.3)16Fe78B6 were prepared using melt-spinning method.X-ray diffractometer(XRD)and vibration sample magnetometer(VSM)were used to analyze the relationship of phase composition,magnetic properties.(4)On the basis of the review of phase diagram data and thermodynamic properties,the RE-B(RE=Dy,Lu)binary systems were optimized using the CALPHAD method.Self-consiste thermodynamic parameters of the RE-B(RE=Dy,Lu)binary systems were obtained finially.The calculated phase diagrams and thermodynamic properties are in good agreement with the experimental results and calculated results in the litereature.