【摘要】 【目的】稀土永磁材料的研究最早可以追溯到20世纪60年代，人们研究稀土元素与铁、钴等金属构成的合金后发现，此类合金具有较强的磁性能，然而初期获得的磁性材料性能不稳定，限制了其实际应用。NdFeB磁体因具有优良的磁性能被应用于医学领域的核磁共振仪器、能源行业的发电机、新能源汽车的牵引电机等，但因磁体矫顽力较低且耐蚀性能较差，限制了其在高温、高湿恶劣环境中的应用。【方法】采用先进纳米技术制备合金纳米粉来改善烧结NdFeB(S-NdFeB)磁体的磁性能和耐蚀性能。首先采用直流电弧法制备Cu-Sn合金纳米粉，将其与经过快速冷却、气流磨研制备的NdFeB微米粉均匀混合，再经真空1 080℃高温烧结和960℃、450℃二次回火处理得到初胚，并对初胚进行线切割和抛光处理，然后对具有不同Cu-Sn合金纳米粉添加量的S-NdFeB磁体进行性能测试和形貌表征。【结果】采用直流电弧法制备的Cu-Sn合金纳米粉形貌为类球状，其平均粒径约为40 nm。Cu-Sn合金纳米粉能够有效改变S-NdFeB磁体的晶界电位，降低液相烧结温度，并可从晶界处渗进主相表层以改善S-NdFeB磁体的耐蚀性能、磁体密度和内禀矫顽力。在S-NdFeB微米级磁粉中，添加适量Cu-Sn合金纳米粉可以改善磁体的主相均匀性与晶界润湿性。当添加质量分数为0.4%的Cu-Sn合金纳米粉后，S-NdFeB磁体的内禀矫顽力可达1 031 k A/m，剩磁为1.28 T，比未添加Cu-Sn合金纳米粉时分别约提升9.8%和4.1%。添加质量分数为0.2%的Cu-Sn合金纳米粉后，与未添加合金纳米粉时相比，S-NdFeB磁体的腐蚀电位从-0.851 V提升至-0.728 V，腐蚀电流密度从53.12μA/cm~2降低到42.19μA/cm~2，改变量分别约为14.5%与-20.6%，因而Cu-Sn合金纳米粉的适量添加使得S-NdFeB磁体的耐蚀性能得到了明显改善。【结论】由直流电弧法制备的Cu-Sn合金纳米粉经过真空混合烧结等处理后，可以改善S-NdFeB磁体的晶界电位与液相烧结温度，并可通过晶界扩散改变主相表面层结构。在保持磁性不变的前提下，Cu-Sn合金纳米粉能够改善NdFeB磁体的耐蚀性能、提升内禀矫顽力、节约重稀土资源和降低成本，因而添加Cu-Sn合金纳米粉对改善NdFeB磁体的磁性能和耐蚀性能具有重要意义。更多还原

【Abstract】 [Objective]The research on rare earth permanent magnet materials can be traced back to the1 960 s at the earliest. At that time,after studying the alloys composed of rare earth elements and metals such as iron and cobalt,it was found that these alloys had strong magnetic properties. However,the properties of magnetic materials obtained at the initial stage are unstable,thus limiting their practical application. Due to their excellent magnetic properties,NdFeB magnets are applied to nuclear magnetic resonance instruments in the medical field,generators in the energy industry,and traction motors of newenergy vehicles. However,their application is limited by the lowcoercive force and poor corrosion resistance of magnets in harsh high-temperature and high-humidity environments. [Methods]Advanced nanotechnology was adopted to prepare alloy nanosized powders to improve the magnetic properties and corrosion resistance of sintered NdFeB( S-NdFeB) magnets. First,Cu-Sn alloy nanosized powder prepared by the direct current( DC) arc method was uniformly mixed wth NdFeB micro-powder developed by rapid cooling and air flowgrinding.Then,the initial blanks were obtained via vacuum sintering at 1 080 ℃ and secondary tempering at 960 ℃and 450 ℃ ． Additionally,the blanks were processed by wire cutting and polishing. Finally,property tests and morphology characterizations were conducted on S-NdFeB magnets wth different contents of Cu-Sn alloy nanosized powders. [Results]The results showthat the Cu-Sn alloy nanosized powder prepared by the DC arc method has quasi-spherical morphology,and its average particle size is about 40 nm. Cu-Sn alloy nanosized powders can effectively alter the potential at the grain boundaries of S-NdFeB,lower the liquid-phase sintering temperature,and penetrate the main phase surface layer from the grain boundaries to improve corrosion resistance,magnetic density,and intrinsic coercive force. In S-NdFeB micron-sized magnetic powders,the uniformity of the main phase in the magnet and wettability of the grain boundaries can be improved by adding an appropriate amount of Cu-Sn alloy nanosized powders. Under the addition of Cu-Sn alloy nanosized powders wth a mass fraction of 0. 4%,the intrinsic coercive force of the S-NdFeB magnet can reach 1 031 kA/m,and the residual magnetism is 1. 28 T,which increase by 9. 8% and 4. 1%respectively compared wth the situation wthout the addition of nanosized powders. After adding the Cu-Sn alloy nanosized powders wth a mass fraction of 0. 2%,the corrosion potential of the S-NdFeB magnet is increased from-0. 851 V to-0. 728 V,the corrosion current density is decreased from 53. 12 μA/cm~2 to42. 19 μA/cm~2,and the change amounts are 14. 5% and-20. 6% respectively compared with the situation wthout the addition of alloy nanosized powders. Therefore,a significant improvement in the corrosion resistance of the S-NdFeB magnet can be achieved by the appropriate addition of Cu-Sn alloy nanosized powders. [Conclusions]The Cu-Sn alloy nanosized powders prepared by the DC arc method can improve the grain boundary potential and liquid-phase sintering temperature of S-NdFeB magnets after mixed vacuum sintering,and change the surface layer structure of the main phase via grain boundary diffusion. Under the premise of keeping the magnetic properties unchanged, Cu-Sn alloy nanosized powders can improve corrosion resistance of NdFeB magnets and intrinsic coercive force,conserve heavy rare earth resources,and reduce costs. Thus,it is of great significance to improve the magnetic properties and corrosion resistance of magnets by employing Cu-Sn alloy nanosized powders.更多还原