Phase Equilibria Of Rare Earth Permanent Magnet Material In Some Optimization And Application

Rare-earth permanent magnetic materials have been widely used in the fields of communication,transportation,medical and aerospace, owing to their extraordinarily high remanence,high coercivity and high magnetic energy product.The development of reasonable,self-consistent and reliable thermodynamic database of rare-earth permanent magnetic materials and the investigation of microstructure evolution during a variety of manufacturing process have both significantly theoretical and practical values to alloy design and process optimization.In this work, the related phase equilibria relationships and applications of part of rare-earth magnetic materials were investigated using CALPHAD method. This work mainly focuses on:1.Nd-B and Cr-Nd binary systems,Fe-Nd-B and Fe-Cr-B ternary systems were thermodynamically reassessed with the aim of obtaining more reasonable thermodynamic parameters and more accurate phase relations.B-Nd-Cr and Fe-Nd-Cr ternary systems were optimized.Based on the metastable experimental information,the reasonable, self-consistent and comprehensive thermodynamic description of Fe-Nd-B-Cr quaternary system considering metastable phases Fe₃B, Fe₂₃Nd₂B₃ and Fe₁₇Nd₂B was developed.2.Based on the obtained thermodynamic database and CALPHAD technique,alloy design and microstructure evolution concerning Fe-Nd-B magnetic materials were investigated.Solidification behavior under different cooling rate;isothermal phase transformations and phase precipitate sequence at various melt undercoolings were analyzed and predicted using step rule and largest driving force crietia respectively according to the different situations.3.Co-Ho binary system was thermodynamically optimized.The calculated results can reproduce well the corresponding experimental data. A set of self-consistent thermodynamic parameters describing various phases in this binary system has been obtained.