Research On The Mechanical Milling And Crystallization Treatment Of The Nd₂Fe₁₄B/α-Fe Magnetic Material

Nano-composite Nd2Fe14B/α-Fe magnetic material has been prepared by mechanical milling Nd2Fe14B alloy under Ar2 and subsequent crystallization at different temperature. Effect of ball milling (attritor mechanical milling and planetary mechanical milling) and crystallization technique on structure and magnetic of nanocomposite Nd2Fe14B alloy has been analyzed by XRD, SEM, TEM and PPMS.The results indicated that more perfect alloy powders was obtained by attritor mechanical milling with upper efficiency. Nd2Fe14B grain refined quickly with increasing milling time and disappeared. The grain size ofα-Fe decreased with increasing milling time, the Nd-Fe-B alloy powders was composed of amorphous phase Nd2Fe14B andα-Fe with average grain size of about 10nm after milling 5 hours. And the alloy powders distributed symmetrically with powders size of about 0.2-0.3μm.The crystallization behavior of amorphous Nd2Fe14B powders with mechanical milling 5 hours was studied. During the process of crystallization treatment, the average grain sizes of the alloy powders were growing with increasing temperature of crystallization. And generally speaking, the grain sizes were all less than 100nm. The average grain sizes of Nd2Fe14B andα-Fe reached a minimum of sizes after crystallization treatment (temperature of crystallization: 650℃; heat preservation time: 5 hours). The average grain size of Nd2Fe14B was about 40nm, and the average grain size ofα-Fe was about 40nm. Moreover the optimal magnetic properties of the material has been obtained under the above conditions of crystallization treatment: Br=1.06T, Hci=347kA/m,(BH)m=142kJ/m3.