烧结NdFeB断裂方式及其断面的微观结构

经熔炼、制粉、成型、烧结和回火等工序制备了成分为Nd33Fe65.95B1.05(质量分数)的烧结NdFeB磁体，将铸锭样品和烧结磁体样品折断，并采用扫描电子显微镜和金相显微镜对二者的断裂方式和断面的微观结构进行了对比分析。结果表明：烧结NdFeB铸锭的断裂方式为沿晶断裂，断面处有较多的层状富钕相，多边形的主相较为完整;烧结NdFeB磁体既有沿晶断裂也有穿晶断裂，但是以沿晶断裂为主。分析造成烧结NdFeB磁体断裂的原因为：(1)其微观结构中有大量的孔洞等缺陷，这是外部原因；(2)微观结构中占主要成分的主相的维氏硬度为6 235.94 N·mm-2，富钕相的维氏硬度为5 947.42 N·mm-2，二者有较大的差距，这是本征因素。针对磁体中孔洞和夹杂等缺陷存在而造成的断裂提出了相应的解决措施。

Abstract

The sintered permanent magnets of Nd33Fe65.95B1.05 were prepared via smelting, powdering, forming, sintering and tempering process. The mode and microstructure of the fracture surface were researched by SEM and metallographic microscope. It was showed that the fracture surfaces of the ingot are intergranuler fracture for its big brittleness and there are many Nd-rich phases at fracture surface but Nd2Fe14B phases are relatively integrated. The fracture mode of sintered NdFeB magnets is intergranuler fracture and transgranular fracture because there are lots of defects in magnets, however, their fracture mode is primarily intergranuler fracture. There are two factors accounting to the facture of sintered NdFeB magnets. The extrinsic factor is that there are a good deal of defects, such as holes and impurities. The intrinsic factor is the difference of Vickers hardness of Nd2Fe14B phase and Nd-phase in sintered NdFeB magent. The numerical value of the former Vickers hardness is 6 235.94 N·mm-2, but that of the latter Vickers hardness is 5 947.42 N·mm-2. To control the fracture of sintered NdFeB magnet, some methods of decreasing holes and impurities are proposed.

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唐杰, 张林, 魏成富, 杨梨容, 赵导文. 烧结NdFeB断裂方式及其断面的微观结构[J]. 强激光与粒子束, 2011, 23(6): 1509. Tang Jie, Zhang Lin, Wei Chengfu, Yang Lirong, Zhao Daowen. Fracture mode of sintered NdFeB alloy and microstructure of fracture surface[J]. High Power Laser and Particle Beams, 2011, 23(6): 1509.

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