氮添加量对块体纳米晶NdFeB永磁材料的影响

Effects of Nitrogen Addition on Bulk Nanocrystalline NdFeB Permanent Magnets

通过铜模吸铸法制备Φ2 mm的棒状Nd8.5Fe65.5 Ti2ZrNbB 22-xNx(x=0~2,原子分数,%)合金,研究了氮添加量对样品微结构、室温和高温磁性能、耐腐蚀性能的影响。结果表明,添加氮元素可以细化晶粒,抑制Nd19Fe68 B68相的生成,促进Nd 2Fe14B永磁相的生成,显著提高样品的磁性能、温度稳定性和耐腐蚀性能。当x=1时,样品的室温磁性能、高温磁性能和耐腐蚀性能均达到最佳。与x=0的样品相比,x=1的样品的室温内禀矫顽力iHc、剩磁B r和最大磁能积(BH)max分别提高了70.6%、14.6%和100.0%;25~180℃温度范围内的剩磁温度系数α和矫顽力温度系数β的绝对值分别降低了36.1%和19.7%;25~250℃温度范围内的磁通不可逆损失Hirr从-30.8%/K提高到-19.6%/K;自腐蚀电位E corr从-0.979 V升高到-0.784 V,自腐蚀电流I corr从1.054×10^-4 A/cm^2下降到1.736×10^-5 A/cm^2。

The bulk nanocrystalline magnets of Nd8.5Fe65.5 Ti2ZrNbB22-xNx(x=0—2,at%)in the rod form with 2 mm diameter were prepared by copper mold suction casting.The effects of nitrogen addition on the microstructure,room-temperature and high-temperature magnetic properties,and corrosion resistance of the samples were studied.It is shown that the N addition can refine the grains,inhibit the formation of Nd19Fe68B68 phase,and promote the formation of Nd 2Fe 14 B permanent magnetic phase.Thus,the magnetic properties,thermal stability and corrosion resis-tance of the samples are significantly improved.The sample with x=1 exhibited the best room-temperature and high-temperature magnetic properties,and the best corrosion resistance.As compared to the sample with x=0,the intrinsic coercivity i H c,the remanence B r and the maximum energy product(BH)max of the sample with x=1 at room temperature increased by 70.6%,14.6%and 100.0%,respectively.At the same time,in the temperature range of 25—180℃,the absolute values of the temperature coefficientsαandβfor the remanence and coercivity decrease by 36.1%and 19.7%,respectively.The flux irreversible loss in the temperature range of 25—250℃increases from-30.8%/K for the sample with x=0 to-19.6%/K for the sample with x=1.Furthermore,as x increases from 0 to 1,the corrosion potential E corr increases from-0.979 V to-0.784 V,and the corrosion current density I corr decreases from 1.054×10^-4 A/cm^2 to 1.736×10^-5 A/cm^2.