The present paper describes the effect of alloy composition,homogenization and dehy-drogenization procedures on magnetic properties of NdFeB type of HDDR powders and the bonded magnet.The results showed that the powde...The present paper describes the effect of alloy composition,homogenization and dehy-drogenization procedures on magnetic properties of NdFeB type of HDDR powders and the bonded magnet.The results showed that the powders prepared by HDDR process possesses useful magnetic proper- ties and a better thermal stability than the sintered NdFeB magnet does.展开更多
The recombination stage of the HDDR process of Sm 2Fe 17 compound was investigated by X ray AFM and VSM. Hydrogen treatment at 750℃ for 3 h makes the Sm 2Fe 17 compound disproportionate completely into ...The recombination stage of the HDDR process of Sm 2Fe 17 compound was investigated by X ray AFM and VSM. Hydrogen treatment at 750℃ for 3 h makes the Sm 2Fe 17 compound disproportionate completely into α Fe and SmH 2 with grain sizes ranging from a few to 20 nm. These grains aggregate into short rod like aggregations. Because of the very short mutual diffusion distances between Sm and Fe atoms, α Fe and SmH 2 recombine into Sm 2Fe 17 very quickly. For only 1 min of dehydrogenation, a small amount of Sm 2Fe 17 compound is formed, and the recombination reaction is completed in 5～10 min.展开更多
The demagnetization process and the coercivity mechanism for amsotropic HDDR Nd(Fe,Co)B bonded magnets were studied by comparing the dependence of coercivity on the alignment field applied while the powders were press...The demagnetization process and the coercivity mechanism for amsotropic HDDR Nd(Fe,Co)B bonded magnets were studied by comparing the dependence of coercivity on the alignment field applied while the powders were pressed. The results showed that both the remanence and the coercivity of magnet increased with increasing alignment field. The demagnetization process of the magnet can be classified as the nucleation process inside the grains and the domain-wall motion between the grains. The combined effect of two processes determines the coercivity of HDDR NdFeB bonded magnets.展开更多
未经均匀化热处理的纯三元及含Zr,Ga元素的SC合金铸片经优化的HDDR工艺处理都可以制备各向异性Nd Fe B磁粉.这表明:元素的添加及SC铸片是否进行了均匀化热处理都不是HDDR磁粉各向异性形成的必要条件.磁粉各向异性形成的关键因素在于HDD...未经均匀化热处理的纯三元及含Zr,Ga元素的SC合金铸片经优化的HDDR工艺处理都可以制备各向异性Nd Fe B磁粉.这表明:元素的添加及SC铸片是否进行了均匀化热处理都不是HDDR磁粉各向异性形成的必要条件.磁粉各向异性形成的关键因素在于HDDR工艺的调节,即适当地加快歧化反应过程,减缓脱氢再结合过程以及控制脱氢再结合时的合适氢气压强均有利于磁粉各向异性的形成.本文将为制备低成本高各向异性磁粉提供重要的指导.展开更多
文摘The present paper describes the effect of alloy composition,homogenization and dehy-drogenization procedures on magnetic properties of NdFeB type of HDDR powders and the bonded magnet.The results showed that the powders prepared by HDDR process possesses useful magnetic proper- ties and a better thermal stability than the sintered NdFeB magnet does.
文摘The recombination stage of the HDDR process of Sm 2Fe 17 compound was investigated by X ray AFM and VSM. Hydrogen treatment at 750℃ for 3 h makes the Sm 2Fe 17 compound disproportionate completely into α Fe and SmH 2 with grain sizes ranging from a few to 20 nm. These grains aggregate into short rod like aggregations. Because of the very short mutual diffusion distances between Sm and Fe atoms, α Fe and SmH 2 recombine into Sm 2Fe 17 very quickly. For only 1 min of dehydrogenation, a small amount of Sm 2Fe 17 compound is formed, and the recombination reaction is completed in 5～10 min.
文摘The demagnetization process and the coercivity mechanism for amsotropic HDDR Nd(Fe,Co)B bonded magnets were studied by comparing the dependence of coercivity on the alignment field applied while the powders were pressed. The results showed that both the remanence and the coercivity of magnet increased with increasing alignment field. The demagnetization process of the magnet can be classified as the nucleation process inside the grains and the domain-wall motion between the grains. The combined effect of two processes determines the coercivity of HDDR NdFeB bonded magnets.
文摘未经均匀化热处理的纯三元及含Zr,Ga元素的SC合金铸片经优化的HDDR工艺处理都可以制备各向异性Nd Fe B磁粉.这表明:元素的添加及SC铸片是否进行了均匀化热处理都不是HDDR磁粉各向异性形成的必要条件.磁粉各向异性形成的关键因素在于HDDR工艺的调节,即适当地加快歧化反应过程,减缓脱氢再结合过程以及控制脱氢再结合时的合适氢气压强均有利于磁粉各向异性的形成.本文将为制备低成本高各向异性磁粉提供重要的指导.
