CuGa晶界添加对烧结钕铁硼永磁体磁性能及热稳定性的影响

Effect of CuGa Intergranular Addition on the Magnetic Property and Thermal Stability of Sintered NdFeB Magnets

将商用N45磁粉与CuGa辅合金粉末混合制备得到烧结钕铁硼磁体。CuGa辅合金的添加优化了磁体的晶界,使得磁隔绝效应更加显著,从而提高了磁体的磁性能及热稳定性。仅需添加0.1%质量分数的Ga,烧结磁体矫顽力就由12.5 kOe增长到13.4 kOe,继续增加添加量虽然有利于提高矫顽力,但是降低了磁体的剩磁。EDS结果显示,在晶粒边界处有Cu和Ga的富集现象,可以很好的起到去磁耦合的作用,由于边界在磁体中占比极小,故较多的添加量会使辅合金元素进入主相,降低磁性能。随着辅合金添加量的增加,磁体的矫顽力温度系数单调的由-0.677%/℃变化为-0.661%/℃。CuGa辅合金添加磁体的矫顽力温度系数的绝对值小于未添加磁体,说明随着CuGa辅合金添加量的增加,磁体的矫顽力热稳定性有所提高。100℃处理后,未添加CuGa辅合金磁体(Pc=2)磁通不可逆损失hirr=14.14%,而添加了质量分数为0.1%、0.3%和0.5%的Ga的样品hirr分别为8.07%,5.75%,5.35%。CuGa合金添加可以减小磁通的不可逆损失,使磁体的热稳定性得到改善,有利于磁体在电机等高温环境中的应用。

Sintered NdFeB magnets have been prepared with the CuGa intergranular addition in N45 commercial powder.The addition of CuGa optimizes the grain boundary of sintered magnets,which can enhance the magnetic isolation and improve the magnetic properties and thermal stability.The coercivity of sintered magnet increased from 12.5 kOe to13.4 kOe with only 0.1%Ga addition,and more addition can enhance coercivity further but lower the remenance.EDS results shows that the enrichment of Cu and Ga in grain boundary can make a good magnetic isolation,but excessive addition would bring these two elements in main phase and suppress the magnetic properties since the grain boundary has a small proportion.With the increasing of addition,the temperature coefficient of coercivity changed from-0.677%/℃to-0.661%/℃gradually.The lower absolute value of temperature coefficient of coercivity with addition of CuGa proves that the thermal stability of the magnet has been improved.After 100℃treatment,the irreversible loss of the magnetic flux(hirr)of original magnet(Pc=2)is 14.14%,while hirr of magnets with 0.1,0.3 and 0.5%Ga addition is 8.07%,5.75%,5.35%,respectively.The addition of CuGa can decrease hirr and improve the thermal stability of the magnets,which would be beneficial to it’s high temperature application,such as electromotor.