Study On The Preparation And Magnetic Properties Of ThMn12-type Nd-Fe-N Permanent Magnetic Material

In this paper,Nd(FeMo)12 alloy ingot was prepared using maglev smelting furnace,the melting process was studied,and the single phase Nd(FeMo)12 ingot was obtained by vacuum heat treatment.Nd(FeMo)12Nx were prepared through crushing and nitriding the ingot.The effect of particle size and nitriding temperature on nitriding process was studied,and the evolution of magnetic properties for Nd(FeMo)12N in the process of grinding was investigated.The results indicates that it is easier to obtained alloy ingot with uniform composition by using low melting point FeMo alloy instead of pure Mo during magnetic levitation melting,and the single phase Nd(FeMo)12 alloy can be prepared by 72 h of cacuum heat treatment at 1000 ?.The alloy exhibits tipical soft magnetic properties after heat treatment.The particles with average size of 50 ?m and 5 ?m was nitrided,it was found that powders with small size exhibit a higher nitrogen content and excellent magnetic properties after nitriding at the same condition.As the nitridation temperature increases from 480 ? to 580 ?,the nitrogen content of the powder after nitriding increases,the lattice parameter increases,and the volume of the unit cell expands,the magnetic properties of powders changed significantly after nitriding.The formation and decomposition of nitridation tend to balance when the nitridation temperature reaches 550 ?,the nitrogen content of the powders tend to be stable or even decrease when the nitridation tempetature is high than 550 ?.The patticle size of nitride powders decreases rapidly during early brief time grinding,and the grain size decreases during grinding.The powder size decreases slowly when the size is less than 2 ?m,and there is no phase change in the grinding process.The coercivity of powders increases with the increase of grinding time,and the saturation magnetization decreases slightly after grinding.Nd(FeMo)12N1.52 powder obtained exhibits significant c-axis orientation and excellent magnetic properties with saturation magnetization of 100.5 emu/g,coercivity of 3500 Oe,respectively.The powders exhibit a magnetocrystalline anisotropy of 11 T,and a curie temperature of 598 K,respectively.The nitride decomposes at 845 K.