Using pure Sm and Fe powders as starting materials,high coercive Sm-Fe-N mag- nets have been prepared by mechanical alloying in combination with beat treatment and nitriding.The best result is:_iH_c=33.1 kA/cm(41.6 kO...Using pure Sm and Fe powders as starting materials,high coercive Sm-Fe-N mag- nets have been prepared by mechanical alloying in combination with beat treatment and nitriding.The best result is:_iH_c=33.1 kA/cm(41.6 kOe)and(BH)_(max)=98.7 kJ/cm^3(12.4 MGOe).The phases formed in the specimens during mechanical alloying, crystallizing and nitriding processes were examined by X-ray diffraction technique.The magnetic properties of the specimens were measured with the pulsed magnetometer in field up to 12 T.Experimental results show that mechanical alloying is an efficient ap- proach for preparing high coercive magnets.As an important factor for obtaining a high coercivity,the grain sizes of magnets are about tens of nanometer.The presence of some soft magnetic phases in the specimens leads to a neck on the demagnetization curve.展开更多
Isotropic Sm-Fe-N bonded magnets were obtained by additive manufacturing(AM). The technique used was the so-called powder bed fusion(PBF) and the feedstock was composed of a polymeric binder(PA-12) and Sm-Fe-N flake p...Isotropic Sm-Fe-N bonded magnets were obtained by additive manufacturing(AM). The technique used was the so-called powder bed fusion(PBF) and the feedstock was composed of a polymeric binder(PA-12) and Sm-Fe-N flake particles(Nitroquench-P). The AM set-up equipment uses a computer-controlled CO2 laser beam to melt the binder and constructs magnets layer-by-layer. In order to develop this study, a cylinder with 10 mm of both height and diameter was selected as the shape of samples. Specimens were analyzed by scanning electron microscopy(SEM) and X-ray diffraction(XRD). Magnetic properties were measured in a hysteresis graph. XRD results indicate that there is no degradation of the main magnetic phase(SmFe7 Nx). In the AM component, porous regions were identified on SEM micrographs, as well as magnetic particles and polymeric binder. Remanence values(Br) as great as 0.3 T are achieved, while intrinsic coercivities remain in the range from 616 up to 642 kA/m. An additional isostatic compression of the parts results in greater remanence, which is directly proportional to the density increase. Coercivity is also sensitive to the porosity decrease, probably due to a better interlocking of particles. Current results indicate AM as a promising route for near net-shape manufacturing of Sm-Fe-N permanent magnets, a market niche yet to be widely explored.展开更多
Sm2Fe17-xNbx （x = 0-4） powder was synthesized by HDDR treatment and nitrogenation. The effects of partial Nb substitution for Fe on the structural and magnetic properties of Sm2Fe17-xNbx alloys and their nitlides we...Sm2Fe17-xNbx （x = 0-4） powder was synthesized by HDDR treatment and nitrogenation. The effects of partial Nb substitution for Fe on the structural and magnetic properties of Sm2Fe17-xNbx alloys and their nitlides were investigated. It was seen that Sm2（Fe,Nb）17 phase exists in both annealed and HDDR-treated Sm2Fe17-xNbx alloys. However, its content is decreased with the increase in Nb substitution. In annealed alloys, Sm2（Fe,Nb）17 phase becomes unstable and will dissociate into SmFe2 and Fe-rich phases when x 〉 1.5. With HDDR-treatment, the Nb concentration in recombined Sm2（Fe,Nb）17 phase is decreased, and the content of Fe-rich phases is increased. Sm2Fe17-xNbx powder exhibits dendritic cracks and fine particles with a size of less than 300 nm. In nitrogenated alloys, N atoms mainly enter 2：17-type phase to form Sm2（Fe,Nb）17Ny. Partial Nb atoms in Sm2（Fe,Nb）17Ny phase will be released or excluded by nitrogen atoms. Fe-rich phases increase, and are followed by the amorphous Sm2（Fe,Nb）17Ny phase. Nb substitution for Fe with x = 0.5 and 1.0 in Sm2Fe17-xNbxNy powders increases the coercivity and remanence. But when x is greater than 2.0, Nb substitution will deteriorate the magnetic properties.展开更多
文摘Using pure Sm and Fe powders as starting materials,high coercive Sm-Fe-N mag- nets have been prepared by mechanical alloying in combination with beat treatment and nitriding.The best result is:_iH_c=33.1 kA/cm(41.6 kOe)and(BH)_(max)=98.7 kJ/cm^3(12.4 MGOe).The phases formed in the specimens during mechanical alloying, crystallizing and nitriding processes were examined by X-ray diffraction technique.The magnetic properties of the specimens were measured with the pulsed magnetometer in field up to 12 T.Experimental results show that mechanical alloying is an efficient ap- proach for preparing high coercive magnets.As an important factor for obtaining a high coercivity,the grain sizes of magnets are about tens of nanometer.The presence of some soft magnetic phases in the specimens leads to a neck on the demagnetization curve.
文摘Isotropic Sm-Fe-N bonded magnets were obtained by additive manufacturing(AM). The technique used was the so-called powder bed fusion(PBF) and the feedstock was composed of a polymeric binder(PA-12) and Sm-Fe-N flake particles(Nitroquench-P). The AM set-up equipment uses a computer-controlled CO2 laser beam to melt the binder and constructs magnets layer-by-layer. In order to develop this study, a cylinder with 10 mm of both height and diameter was selected as the shape of samples. Specimens were analyzed by scanning electron microscopy(SEM) and X-ray diffraction(XRD). Magnetic properties were measured in a hysteresis graph. XRD results indicate that there is no degradation of the main magnetic phase(SmFe7 Nx). In the AM component, porous regions were identified on SEM micrographs, as well as magnetic particles and polymeric binder. Remanence values(Br) as great as 0.3 T are achieved, while intrinsic coercivities remain in the range from 616 up to 642 kA/m. An additional isostatic compression of the parts results in greater remanence, which is directly proportional to the density increase. Coercivity is also sensitive to the porosity decrease, probably due to a better interlocking of particles. Current results indicate AM as a promising route for near net-shape manufacturing of Sm-Fe-N permanent magnets, a market niche yet to be widely explored.
基金This work was financially supported by the National Natural Sciences Foundation of China (No. 50271024) and the Natu-ral Science Foundation of Hebei Province, China (No.501013).
文摘Sm2Fe17-xNbx （x = 0-4） powder was synthesized by HDDR treatment and nitrogenation. The effects of partial Nb substitution for Fe on the structural and magnetic properties of Sm2Fe17-xNbx alloys and their nitlides were investigated. It was seen that Sm2（Fe,Nb）17 phase exists in both annealed and HDDR-treated Sm2Fe17-xNbx alloys. However, its content is decreased with the increase in Nb substitution. In annealed alloys, Sm2（Fe,Nb）17 phase becomes unstable and will dissociate into SmFe2 and Fe-rich phases when x 〉 1.5. With HDDR-treatment, the Nb concentration in recombined Sm2（Fe,Nb）17 phase is decreased, and the content of Fe-rich phases is increased. Sm2Fe17-xNbx powder exhibits dendritic cracks and fine particles with a size of less than 300 nm. In nitrogenated alloys, N atoms mainly enter 2：17-type phase to form Sm2（Fe,Nb）17Ny. Partial Nb atoms in Sm2（Fe,Nb）17Ny phase will be released or excluded by nitrogen atoms. Fe-rich phases increase, and are followed by the amorphous Sm2（Fe,Nb）17Ny phase. Nb substitution for Fe with x = 0.5 and 1.0 in Sm2Fe17-xNbxNy powders increases the coercivity and remanence. But when x is greater than 2.0, Nb substitution will deteriorate the magnetic properties.
