Nd-Fe-B速凝合金晶界相组成与组织结构研究  

Phase Composition and Microstructure of Grain Boundaries in Nd-Fe-B Strip Casting Flakes

作　　者：李彦儒 李安华[1] 冯海波[1] 李卫[1] Li Yanru;Li Anhua;Feng Haibo;Li Wei(Institute of Functional Materials,Central Iron&Steel ResearchInstituteComporation,Beijing 100081,China)

机构地区：[1]钢铁研究总院有限公司功能材料研究院,北京100081

出　　处：《中国稀土学报》2024年第2期236-244,I0002,共10页Journal of the Chinese Society of Rare Earths

基　　金：国家重点研发计划项目(2021YFB3503001)资助。

摘　　要：钕铁硼烧结磁体中的晶界相组成、微结构及化学成分对其矫顽力有重要的影响,为了阐明钕铁硼烧结磁体中晶界相组成和微观组织结构的演变机制,有必要对其先驱体材料Nd-Fe-B速凝合金片中晶界富Nd相的相组成和微结构特点进行研究。采用速凝工艺制备Nd-Fe-B速凝合金片,重点对速凝合金的晶界区域进行TEM研究。研究发现:在富Nd三角晶界存在两种衬度明显不同的区域,衬度均匀一致的区域为非晶微晶相,在衬度明暗对比的区域发现有双六方结构的Nd相(dhcp-Nd)、低熔点共晶相"Nd+Nd_(2)Fe_(14)B"和和少量非晶微晶相存在。晶界线扫描结果表明,晶界区域的Nd:Fe原子比并非恒定值,晶界非晶微晶区的Fe含量较高,其Fe含量平均值大于60%(原子分数);而晶界晶化区的成分波动较大,这可能是因为该区域是dhcp-Nd相、"Nd+Nd_(2)Fe_(14)B"共晶相以及少量非晶微晶相的混合物。在钕铁硼合金的晶界处普遍存在非晶相,是因为Nd-Fe-B合金体系属于深共晶体系,合金熔液在冷却过程中提早凝固,无序状态亚稳到室温造成的。The grain-boundary(GB)phase composition and microstructure have an important influence on the coercivity of sintered Nd-Fe-B magnets.In order to clarify the evolution mechanism of the GB phase composition and microstructure of sintered magnets,it is necessary to study the GB characteristics of Nd-Fe-B strip casting(SC)flakes as the precursor of the magnets.The Nd-Fe-B SC flakes were prepared by vacuum induction melting SC technology.TEM investigation of the phase composition and microstructure of grain boundaries in Nd-Fe-B SC flakes were carried out.It is found that there are two areas with obvious different contrast existing in a triangular Nd-rich grain boundary.The area with uniform contrast is amorphous/crystallite.The other area with obvious light and dark contrast contains the double hexagonal close-packed Nd phase(dhcp-Nd),the low meltingpoint eutectic"Nd+Nd_(2)Fe_(14)B"and a trace amount of amorphous/crystallite.The EDS line scan results shows that the atomic ratio of Nd to Fe in the GB regions is not a constant value.In the amorphous/crystallite area,Fe content is higher with an average value of more than 60%;In the crystalline area,the composition fluctuates in a large scale,accompanied with obvious light and dark contrast change,which is probably because the area is a mixture of dhcp-Nd,and eutectic"Nd+Nd_(2)Fe_(14)B"and a trace amount of amorphous/crystallite.Amorphous phase exists commonly in the GB regions of Nd-Fe-B alloys,which is because Nd-Fe-B alloy belongs to deep eutectic system,the alloy liquid tends to solidify earlier than eutectic point during cooling process and form disordered amorphous phase,the meta-stable amorphous remains until room temperature.

关 键 词：Nd-Fe-B速凝合金 晶界 相组成 组织结构 

分 类 号：TM273[一般工业技术—材料科学与工程] TG146[电气工程—电工理论与新技术]