不同工艺烧结钕铁硼磁体的脆性分析

Brittleness Analysis of Sintered NdFeB Magnets in different Processes

不同工艺生产的烧结钕铁硼磁体的脆性(冲击韧性)差异很大。其中,传统工艺磁体的冲击韧性最好,合金锭加氢化工艺磁体稍差,而速凝(SC)加氢化磁体的冲击韧性值仅约为前两者的1/2。扫描电镜断口观测显示不同磁体微观断裂机制不同。传统工艺磁体的裂纹源于主相晶粒内部的解理断裂;合金锭加氢化磁体的裂纹可能起源于主相边界上附着的富钕相颗粒;而SC加氢化磁体的裂纹源于主相的穿晶断裂。XRD分析表明两种氢化磁体脆性差异是因为各自在氢化破碎过程中参与氢化的相不同。合金锭加氢化磁体只有富钕相参与氢化;而SC加氢化磁体主相晶粒参与了氢化。

The brittleness （or impact toughness） of sintered NdFeB magnets processed in different routes are of large difference. Among them the impact toughness of traditional magnet is best; The value of the cast hydrogenated magnet is slightly low; But for SC and hydrogenated magnet, the impact toughness is approximately half of the first two. The SEM observation demonstrates that microscopic fracture mechanisms of these three magnets are different. The cleavage fracture in main phase is the crack source of traditional magnets; For cast and hydrogenated magnets, the crack occurs possibly from the Nd-rich pellets cohered to the main phase boundary; But for SC and hydrogenated magnets the crack source is the transcrystalline break of main phase. The XRD analysis indicates that the brittleness difference of the two hydrogenized magnets is due to different phases participating in hydrogenation. In the cast and hydrogenated magnet only Nd-rich phase is hydrogenated; But the main phase is also hydrogenated in SC and hydro- genated magnet