The effect of Sm-rich liquid phase （Sm2Co3） on magnetic properties and microstructure of 2：17-type Sin-Co magnet was studied. Three phases existed in liquid phase ingot, and took on white, dark grey and grey, respe...The effect of Sm-rich liquid phase （Sm2Co3） on magnetic properties and microstructure of 2：17-type Sin-Co magnet was studied. Three phases existed in liquid phase ingot, and took on white, dark grey and grey, respectively. It was found that the composition of the grey area was similar to the nominal one. Our results indicated that the optimal composition was obtained at 3 wt.% liquid phase added, and the magnetic properties were B^I 1.58 kGs, Hci〉26 kOe, （BH）m=29.51 MGOe. Br increased by 3%, Hci was 13 times larger, and （B/-/）m was 6 times bigger than none liquid phase magnets. Moreover, with the aging time decreasing from 20 to 8 h, the squareness of the demagnetization curves got better, while the coercivity of the samples decreased. It revealed that Sm（Co,Cu）5 phase also precipitated at particle boundaries. It maybe also enhanced the coercivity.展开更多
Sm(Co_(bal)Fe_(0.245)Cu_(0.07)Zr_(0.02))7.8(at%)sintered magnets with high remanence(B_(r)~1.15 T)were prepared using a traditional powder metallurgy method.Tunable magnetic properties,especially intrinsic coercivity(...Sm(Co_(bal)Fe_(0.245)Cu_(0.07)Zr_(0.02))7.8(at%)sintered magnets with high remanence(B_(r)~1.15 T)were prepared using a traditional powder metallurgy method.Tunable magnetic properties,especially intrinsic coercivity(H_(cj)),were obtained through adjusting isothermal procedure parameters.H_(cj)of the magnets increases from 305 to 752 kA·m^(-1)with isothermal annealing time increasing from 3 to 20 h,while B_(r) of the magnets almost keeps constant.From the bright field transmission electron microscopy(TEM)images,it is found that:(1)there is dispersed precipitated phase with very small size in the magnet annealed for 3 h,while the magnets annealed for 20 h have distinct and intact cellular structure;(2)the number density of Z-phase in magnet annealed for 20 h is bigger than that for 3 h.Besides,the finer microstructures were studied with high-resolution transmission electron microscopy(HRTEM).展开更多
The microstructure of twinning as well as the phase boundary between 1:5 H and 2:17 R phase in Fe-rich Sm_(2)Co_(17)-type magnets was characterized at atomic scale using nanobeam diffraction and highresolution STEM-HA...The microstructure of twinning as well as the phase boundary between 1:5 H and 2:17 R phase in Fe-rich Sm_(2)Co_(17)-type magnets was characterized at atomic scale using nanobeam diffraction and highresolution STEM-HAADF imaging,and the reason for the dramatic increase of coercivity during slow cooling was investigated based on the microchemistry analysis.The twinning relationship in the 2:17 R phase originates from ordered substitution of Sm atoms by Co-Co atomic pairs on every three(3033)and(3033)planes,leading to formation of two corresponding equivalent twin variants.The basal plane of the 2:17 R phase,the 1:3 R platelet phase across the 2:17 R cell and the 1:5 H cell boundary phase between two adjacent 2:17 R cells all can act as effective twin boundary.The cell boundary phase is precipitated along the pyramidal habit plane,and a fully coherent phase boundary(PB)is formed between the 1:5 H and 2:17 R phases with the orientation relationship to be PB//(1121)1:5 H//(1011)_(2):17 R.The phase boundary may either be parallel to or intersect with the pyramidal planes occupied by Co-Co atomic pairs.The substantial increase of coercivity during slow cooling is ascribed to the development of large gradient of the elements concentration within the cell boundary phase,resulting in large gradient of domain wall energy,and thus the pinning strength of the cell boundary phase against magnetic domain wall motion is significantly enhanced.展开更多
The as-solution-treated Sm_(2)Co_(17)-type magnets exhibiting a single 1:7 H phase with different average grain sizes(D) were designed.Anisotropy of bending strength(R_(bb))and compressive strength(R_(mc)) of the magn...The as-solution-treated Sm_(2)Co_(17)-type magnets exhibiting a single 1:7 H phase with different average grain sizes(D) were designed.Anisotropy of bending strength(R_(bb))and compressive strength(R_(mc)) of the magnets were investigated.Moreover,the R_(bb) increases from 86 to 173 MPa with D decreasing from~52 to~18 μm for group c//h samples.The Hall-Petch correlation was employed to reveal the effect of grain size on mechanical properties of the magnets,giving deep understanding of the mechanical anisotropy characteristics.The relatively high Hall-Petch coefficient K^(Rbb)(0.79 MPa·m^(1/2)) gives rise to the largest R_(bb)(173 MPa) for group c//h samples.The mechanical anisotropy of the samples is well explained based on crystal structure and grain size features(grain boundaries).Grain refinement is an effective way to enhance the mechanical properties of Sm_(2)Co_(17)-type sintered magnets.展开更多
It is confirmed that the solid solution temperature range to obtain optimal magnetic properties is different for the magnets with different Fe contents,and the correlation between magnetic properties and microstructur...It is confirmed that the solid solution temperature range to obtain optimal magnetic properties is different for the magnets with different Fe contents,and the correlation between magnetic properties and microstructures influenced by solid solution temperature(Ts)has been systematically studied.The optimal solid solution temperature range is 1413-1463 K for the Sm(Co_(bal)Fe_(0.213)Cu_(0.073)Zr_(0.024))_(7.6)magnet,which is higher than that of the Sm(Co_(bal)Fe_(0.262)Cu_(0.073)Zr_(0.024))_(7.6)magnet(1403-1453 K),and the optimal T_s range is about 50 K for both of the magnets.The solid solution temperature range shifting toward relatively high temperature is due to the increase in a phase transition temperature.The magnet solution-treated at proper temperature exhibits 1:7 H single phase,and intact cell structure and high Cu concentration(23.12 at%)in the cell boundary are found after aging process,which makes the magnet shows high intrinsic coercivity(H_(cj))and magnetic field at knee-point(H_(knee)).At a lower solid solution temperature,the 2:17 H,1:5 H and Zr-rich precipitation phases appear,which affects the cell structure,density of lamellar phase and Cu concentration in the cell boundary,leading to the reduced magnetic properties.However,at a higher solid solution temperature,there exist obviously light gray and dark regions with different Sm,Cu and Fe contents in scanning electron microscopy observation,and the magnet shows low pinning field in the two regions and incomplete cell structure,resulting in an inferior H_(cj)and H_(knee).展开更多
In order to counteract the demagnetization caused by eddy current loss,widespread attention has been devoted to increasing the resistivity of permanent magnets.We prepared 2:17-type Sm Co magnets doped with different ...In order to counteract the demagnetization caused by eddy current loss,widespread attention has been devoted to increasing the resistivity of permanent magnets.We prepared 2:17-type Sm Co magnets doped with different ZrO_(2)contents and investigated the influence of the ZrO_(2)content on the magnetic properties and resistive anisotropism.The results showed that not only was the resistivity of the magnet improved,but,in addition,the coercivity of the magnet was significantly increased.The microstructure was studied with TEM,which showed that ZrO_(2)doping was able to cause a decrease in the lamellar phase density and the growth of cellular structures.The increased grain boundaries and Sm_(2)O_(3)phases were favorable to the improvement of resistivity.The decrease of the lamellar phases caused a narrowing of the resistive anisotropism.The additional Cu in the center of the cellular boundaries was the main reason for the enhancement of Hcj.However,an excessive amount caused an increase of the Zr_6(Fe Co)_(23)phase and a deterioration of the cellular structure,thereby leading to a decrease in coercivity.展开更多
The high-temperature magnetic perfo rmance and micro structure of Sm_(1-x)Gd_(x)(Co_(bal)Fe_(0.09)Cu_(0.09)Zr_(0.025))_(7.2)(x=0.3,0.5) magnets were investigated.With the isothermal aging time decreasing from 11 to 3 ...The high-temperature magnetic perfo rmance and micro structure of Sm_(1-x)Gd_(x)(Co_(bal)Fe_(0.09)Cu_(0.09)Zr_(0.025))_(7.2)(x=0.3,0.5) magnets were investigated.With the isothermal aging time decreasing from 11 to 3 h,the temperature coefficient of intrinsic coercivity in the temperature range of 25-500℃,β_(25-500℃),was optimized from -0,167%/℃ to-0.112%/℃ for x=0.3 magnets.The noticeable enhancement(~33%) of temperature stability is correlated with the increased content of 1:5H cell boundary phase and its relatively high Curie temperature as well.However,for the x=0.5 magnet,it is found that the presence of Sm_(5)Co_(19) phases and wider nanotwin variants hinder the formation of 1:5H cell boundary phase.The insufficient 1:5H is not beneficial to the proper redistribution of Cu in cell boundary,making the x=0.5 magnet difficult to achieve higher temperature stability.Consequently,the approach of adjusting the isothermal aging process can offer guidance for attaining superior magnetic performance in the temperature range from 25 to 500℃ for Gd-substituted Sm_(2)Co_(17)-type magnets.展开更多
The unique cellular microstructure of Fe-rich Sm_(2)Co_(17)-type permanent magnets is closely associated with the structure of the solid solution precursor.We investigate the phase structure,magnetic properties,and me...The unique cellular microstructure of Fe-rich Sm_(2)Co_(17)-type permanent magnets is closely associated with the structure of the solid solution precursor.We investigate the phase structure,magnetic properties,and mechanical behavior of B-doped Sm_(2)Co_(17)-type magnets with high Fe content.The doped B atoms can diffuse into the interstitial vacancy,resulting in lattice expansion and promote the homogenization of the phase organizational structure during the solid solution treatment in theory.However,the resulting second phase plays a dominant role to result in more microtwin structures and highly ordered 2:17R phases in the solid solution stage,which inhibits the ordering transformation of 1:7H phase during aging and affects the generation of the cellular structure,and to result in a decrease in magnetic properties,yet the interface formed between it and the matrix phase hinders the movement of dislocations and enhances the mechanical properties.Hence,the precipitation of high flexural strain grain boundary phase induced by B element doping is also a new and effective way to improve the flexural strain of Sm_(2)Co_(17)-type magnets.Our study provides a new understanding of the phase structure evolution and its effect on the magnetic and mechanical properties of Sm_(2)Co_(17)-type magnets with high Fe content.展开更多
In this work,a small amount of Al_(2)O_(3)powders(≤0.3 wt%)were incorporated into the Sm_(2)Co_(17)-type sin-tered magnets,obtaining both high mechanical and magnetic properties.It is found that 0.1%weight percentage...In this work,a small amount of Al_(2)O_(3)powders(≤0.3 wt%)were incorporated into the Sm_(2)Co_(17)-type sin-tered magnets,obtaining both high mechanical and magnetic properties.It is found that 0.1%weight percentage of Al_(2)O_(3)doping is enough to enhance the flexural strength by about 20%(∼180 MPa for the case of the c-axis parallel to height).Meanwhile,the(BH)max remains around 219 kJ/m^(3),and Hcj is 2052 kA/m,which is over 95%of that of the original magnets without doping.The promising improvement in flexural strength is mainly attributed to the grain size effective refinement caused by Sm_(2)O_(3)particles including newly-formed ones from the reaction of the Al_(2)O_(3)powder and Sm in the matrix.Furthermore,the grain size of the magnets decreases significantly with increasing of Al_(2)O_(3)doping up to 0.3 wt%.Espe-cially,the grain size of 0.3 wt%Al_(2)O_(3)doped magnets is refined by 37%.However,the flexural strengths(for the c-axis parallel to height and the c-axis parallel to width cases)of the magnets decrease sequen-tially and are even lower than that of the original magnet.The microstructure investigations indicate that the decrease in flexural strength may closely be correlated to the larger cell size and the incomplete cell boundaries phase.The obtained results infer that the flexural strength is susceptible to not only grain size but also the cellular structure of the magnets.展开更多
以17型车钩装配体为研究对象,利用Altair Hyper Works 10.0软件,对车钩装配体进行网格划分,按照AAR标准,使用ansys12.0软件对车钩装配体进行静强度分析。计算结果表明,应力较大部位与运用中故障多发部位一致,能够较好地反映车钩实际受...以17型车钩装配体为研究对象,利用Altair Hyper Works 10.0软件,对车钩装配体进行网格划分,按照AAR标准,使用ansys12.0软件对车钩装配体进行静强度分析。计算结果表明,应力较大部位与运用中故障多发部位一致,能够较好地反映车钩实际受力状况,为车钩的设计和改进提供参考。展开更多
Influence of Zr contents on high-temperature magnetic performance of Sm(CoFeCuZr)(x=0.025,0.03,0.035,0.04) magnets were investigated.As x increases from 0.025 to 0.04,the temperature coefficient of intrinsic coercivit...Influence of Zr contents on high-temperature magnetic performance of Sm(CoFeCuZr)(x=0.025,0.03,0.035,0.04) magnets were investigated.As x increases from 0.025 to 0.04,the temperature coefficient of intrinsic coercivity(H) is optimized from-0.1673% K^(-1)to-0.1382% K^(-1)and the Hat 773 K gradually increases from 556.32 kA m^(-1)to 667 kA m^(-1).The microstructure and microchemistry of different Zr-content magnets were revealed by a transmission electron microscope equipped with EDS.The increasing Zr content induces that the average size of cells decreases from ~76 nm to ~56 nm and the weight fraction of 1:5 H cell boundary phase increases from ~25% to ~37% as well,resulting decreasing of the average Cu content at cell boundaries from 13.59 at% to ~8.52 at%.It is found that the Cu-lean characteristic at cell boundary phase is the reason that gives rise to higher magnetic properties at elevated temperatures for x=0.04 magnet.展开更多
The excellent thermal stability of magnetic properties of Sm_(2)Co_(17)-based magnets is their most impor-tant feature.However,this stability is reduced when the maximum energy product of Sm_(2)Co_(17)-based magnets i...The excellent thermal stability of magnetic properties of Sm_(2)Co_(17)-based magnets is their most impor-tant feature.However,this stability is reduced when the maximum energy product of Sm_(2)Co_(17)-based magnets is improved,which is mainly determined by the Fe/Cu distribution of the 2:17R cell and 1:5H cell boundary phases.During the demagnetization process,the Cu-rich 1:5H cell boundary phase with a width of 2-15 nm obstructs the motion of the domain walls,yielding coercivity.Herein,we report a micron-scale Cu/Zr-rich and Fe-lean 1:5H-based precipitated phase with a lamellar structure,probably induced by Sm_(2)O_(3) doping.This structure enables the separate regulation of Fe and Cu distribution for Sm_(2)Co_(17)-based magnets with Fe-rich 2:17R cell phases and Cu-rich 1:5H cell boundary phases,consid-erably optimizing the thermal stability of magnetic properties.This discovery can be further developed to produce Sm_(2)Co_(17)-based magnets with high performance and excellent thermal stability of magnetic properties.展开更多
基金supported by the National Natural Science Foundation of China (50871032)National High Technology Research and Development Program of ChinaProgram of Beijing Municipal Science & Technology
文摘The effect of Sm-rich liquid phase （Sm2Co3） on magnetic properties and microstructure of 2：17-type Sin-Co magnet was studied. Three phases existed in liquid phase ingot, and took on white, dark grey and grey, respectively. It was found that the composition of the grey area was similar to the nominal one. Our results indicated that the optimal composition was obtained at 3 wt.% liquid phase added, and the magnetic properties were B^I 1.58 kGs, Hci〉26 kOe, （BH）m=29.51 MGOe. Br increased by 3%, Hci was 13 times larger, and （B/-/）m was 6 times bigger than none liquid phase magnets. Moreover, with the aging time decreasing from 20 to 8 h, the squareness of the demagnetization curves got better, while the coercivity of the samples decreased. It revealed that Sm（Co,Cu）5 phase also precipitated at particle boundaries. It maybe also enhanced the coercivity.
基金the National Basic Research Program of China(No.2014CB643701)the National Natural Science Foundation of China(No.51171048)。
文摘Sm(Co_(bal)Fe_(0.245)Cu_(0.07)Zr_(0.02))7.8(at%)sintered magnets with high remanence(B_(r)~1.15 T)were prepared using a traditional powder metallurgy method.Tunable magnetic properties,especially intrinsic coercivity(H_(cj)),were obtained through adjusting isothermal procedure parameters.H_(cj)of the magnets increases from 305 to 752 kA·m^(-1)with isothermal annealing time increasing from 3 to 20 h,while B_(r) of the magnets almost keeps constant.From the bright field transmission electron microscopy(TEM)images,it is found that:(1)there is dispersed precipitated phase with very small size in the magnet annealed for 3 h,while the magnets annealed for 20 h have distinct and intact cellular structure;(2)the number density of Z-phase in magnet annealed for 20 h is bigger than that for 3 h.Besides,the finer microstructures were studied with high-resolution transmission electron microscopy(HRTEM).
基金Project supported by Zhejiang Province Public Welfare Technology Application Research Project(LGC20E010002)National Natural Science Foundation of China(51877094)。
文摘The microstructure of twinning as well as the phase boundary between 1:5 H and 2:17 R phase in Fe-rich Sm_(2)Co_(17)-type magnets was characterized at atomic scale using nanobeam diffraction and highresolution STEM-HAADF imaging,and the reason for the dramatic increase of coercivity during slow cooling was investigated based on the microchemistry analysis.The twinning relationship in the 2:17 R phase originates from ordered substitution of Sm atoms by Co-Co atomic pairs on every three(3033)and(3033)planes,leading to formation of two corresponding equivalent twin variants.The basal plane of the 2:17 R phase,the 1:3 R platelet phase across the 2:17 R cell and the 1:5 H cell boundary phase between two adjacent 2:17 R cells all can act as effective twin boundary.The cell boundary phase is precipitated along the pyramidal habit plane,and a fully coherent phase boundary(PB)is formed between the 1:5 H and 2:17 R phases with the orientation relationship to be PB//(1121)1:5 H//(1011)_(2):17 R.The phase boundary may either be parallel to or intersect with the pyramidal planes occupied by Co-Co atomic pairs.The substantial increase of coercivity during slow cooling is ascribed to the development of large gradient of the elements concentration within the cell boundary phase,resulting in large gradient of domain wall energy,and thus the pinning strength of the cell boundary phase against magnetic domain wall motion is significantly enhanced.
基金Project supported by the National Natural Science Foundation of China(51871063,51771055)。
文摘The as-solution-treated Sm_(2)Co_(17)-type magnets exhibiting a single 1:7 H phase with different average grain sizes(D) were designed.Anisotropy of bending strength(R_(bb))and compressive strength(R_(mc)) of the magnets were investigated.Moreover,the R_(bb) increases from 86 to 173 MPa with D decreasing from~52 to~18 μm for group c//h samples.The Hall-Petch correlation was employed to reveal the effect of grain size on mechanical properties of the magnets,giving deep understanding of the mechanical anisotropy characteristics.The relatively high Hall-Petch coefficient K^(Rbb)(0.79 MPa·m^(1/2)) gives rise to the largest R_(bb)(173 MPa) for group c//h samples.The mechanical anisotropy of the samples is well explained based on crystal structure and grain size features(grain boundaries).Grain refinement is an effective way to enhance the mechanical properties of Sm_(2)Co_(17)-type sintered magnets.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0700903)the National Natural Science Foundation of China(Nos.51871063 and 51590882)。
文摘It is confirmed that the solid solution temperature range to obtain optimal magnetic properties is different for the magnets with different Fe contents,and the correlation between magnetic properties and microstructures influenced by solid solution temperature(Ts)has been systematically studied.The optimal solid solution temperature range is 1413-1463 K for the Sm(Co_(bal)Fe_(0.213)Cu_(0.073)Zr_(0.024))_(7.6)magnet,which is higher than that of the Sm(Co_(bal)Fe_(0.262)Cu_(0.073)Zr_(0.024))_(7.6)magnet(1403-1453 K),and the optimal T_s range is about 50 K for both of the magnets.The solid solution temperature range shifting toward relatively high temperature is due to the increase in a phase transition temperature.The magnet solution-treated at proper temperature exhibits 1:7 H single phase,and intact cell structure and high Cu concentration(23.12 at%)in the cell boundary are found after aging process,which makes the magnet shows high intrinsic coercivity(H_(cj))and magnetic field at knee-point(H_(knee)).At a lower solid solution temperature,the 2:17 H,1:5 H and Zr-rich precipitation phases appear,which affects the cell structure,density of lamellar phase and Cu concentration in the cell boundary,leading to the reduced magnetic properties.However,at a higher solid solution temperature,there exist obviously light gray and dark regions with different Sm,Cu and Fe contents in scanning electron microscopy observation,and the magnet shows low pinning field in the two regions and incomplete cell structure,resulting in an inferior H_(cj)and H_(knee).
基金the National Natural Science Foundation of China(Grant No.51877094)Ningbo Science and Technology Project(Grant No.2014B11009)。
文摘In order to counteract the demagnetization caused by eddy current loss,widespread attention has been devoted to increasing the resistivity of permanent magnets.We prepared 2:17-type Sm Co magnets doped with different ZrO_(2)contents and investigated the influence of the ZrO_(2)content on the magnetic properties and resistive anisotropism.The results showed that not only was the resistivity of the magnet improved,but,in addition,the coercivity of the magnet was significantly increased.The microstructure was studied with TEM,which showed that ZrO_(2)doping was able to cause a decrease in the lamellar phase density and the growth of cellular structures.The increased grain boundaries and Sm_(2)O_(3)phases were favorable to the improvement of resistivity.The decrease of the lamellar phases caused a narrowing of the resistive anisotropism.The additional Cu in the center of the cellular boundaries was the main reason for the enhancement of Hcj.However,an excessive amount caused an increase of the Zr_6(Fe Co)_(23)phase and a deterioration of the cellular structure,thereby leading to a decrease in coercivity.
基金Project supported by the National Key Research and Development Program of China (2021YFB3503100,2022YFB3505303,2021YFB3501500)the Key Technology Research and Development Program of Shandong Province (2019JZZY020210)。
文摘The high-temperature magnetic perfo rmance and micro structure of Sm_(1-x)Gd_(x)(Co_(bal)Fe_(0.09)Cu_(0.09)Zr_(0.025))_(7.2)(x=0.3,0.5) magnets were investigated.With the isothermal aging time decreasing from 11 to 3 h,the temperature coefficient of intrinsic coercivity in the temperature range of 25-500℃,β_(25-500℃),was optimized from -0,167%/℃ to-0.112%/℃ for x=0.3 magnets.The noticeable enhancement(~33%) of temperature stability is correlated with the increased content of 1:5H cell boundary phase and its relatively high Curie temperature as well.However,for the x=0.5 magnet,it is found that the presence of Sm_(5)Co_(19) phases and wider nanotwin variants hinder the formation of 1:5H cell boundary phase.The insufficient 1:5H is not beneficial to the proper redistribution of Cu in cell boundary,making the x=0.5 magnet difficult to achieve higher temperature stability.Consequently,the approach of adjusting the isothermal aging process can offer guidance for attaining superior magnetic performance in the temperature range from 25 to 500℃ for Gd-substituted Sm_(2)Co_(17)-type magnets.
基金the NationalKey R&D Program of China (Grant Nos. 2021YFB3503102and 2022YFB3505301)Science and Technology Innovation2025 Major Project of Ningbo (Grant No. 2022Z204)+2 种基金ZhejiangProvincial Natural Science Foundation Youth OriginalProject (Grant No. LDQ24E010001)the Key R&D Programof Shanxi Province (Grant No. 202302050201014)Ningbo Natural Science Foundation (Grant No. 2021J216).
文摘The unique cellular microstructure of Fe-rich Sm_(2)Co_(17)-type permanent magnets is closely associated with the structure of the solid solution precursor.We investigate the phase structure,magnetic properties,and mechanical behavior of B-doped Sm_(2)Co_(17)-type magnets with high Fe content.The doped B atoms can diffuse into the interstitial vacancy,resulting in lattice expansion and promote the homogenization of the phase organizational structure during the solid solution treatment in theory.However,the resulting second phase plays a dominant role to result in more microtwin structures and highly ordered 2:17R phases in the solid solution stage,which inhibits the ordering transformation of 1:7H phase during aging and affects the generation of the cellular structure,and to result in a decrease in magnetic properties,yet the interface formed between it and the matrix phase hinders the movement of dislocations and enhances the mechanical properties.Hence,the precipitation of high flexural strain grain boundary phase induced by B element doping is also a new and effective way to improve the flexural strain of Sm_(2)Co_(17)-type magnets.Our study provides a new understanding of the phase structure evolution and its effect on the magnetic and mechanical properties of Sm_(2)Co_(17)-type magnets with high Fe content.
基金supported by the National Key Research and Development Program of China(Nos.2021YFB3503100,2022YFB3505303,2021YFB3501500)the Major Projects in the Inner Mongolia Autonomous Region of China.
文摘In this work,a small amount of Al_(2)O_(3)powders(≤0.3 wt%)were incorporated into the Sm_(2)Co_(17)-type sin-tered magnets,obtaining both high mechanical and magnetic properties.It is found that 0.1%weight percentage of Al_(2)O_(3)doping is enough to enhance the flexural strength by about 20%(∼180 MPa for the case of the c-axis parallel to height).Meanwhile,the(BH)max remains around 219 kJ/m^(3),and Hcj is 2052 kA/m,which is over 95%of that of the original magnets without doping.The promising improvement in flexural strength is mainly attributed to the grain size effective refinement caused by Sm_(2)O_(3)particles including newly-formed ones from the reaction of the Al_(2)O_(3)powder and Sm in the matrix.Furthermore,the grain size of the magnets decreases significantly with increasing of Al_(2)O_(3)doping up to 0.3 wt%.Espe-cially,the grain size of 0.3 wt%Al_(2)O_(3)doped magnets is refined by 37%.However,the flexural strengths(for the c-axis parallel to height and the c-axis parallel to width cases)of the magnets decrease sequen-tially and are even lower than that of the original magnet.The microstructure investigations indicate that the decrease in flexural strength may closely be correlated to the larger cell size and the incomplete cell boundaries phase.The obtained results infer that the flexural strength is susceptible to not only grain size but also the cellular structure of the magnets.
基金partially supported by the National Natural Science Foundation of China (No. 51871063)the Key Technology Research and Development Program of Shandong (No. 2019JZZY020210)。
文摘Influence of Zr contents on high-temperature magnetic performance of Sm(CoFeCuZr)(x=0.025,0.03,0.035,0.04) magnets were investigated.As x increases from 0.025 to 0.04,the temperature coefficient of intrinsic coercivity(H) is optimized from-0.1673% K^(-1)to-0.1382% K^(-1)and the Hat 773 K gradually increases from 556.32 kA m^(-1)to 667 kA m^(-1).The microstructure and microchemistry of different Zr-content magnets were revealed by a transmission electron microscope equipped with EDS.The increasing Zr content induces that the average size of cells decreases from ~76 nm to ~56 nm and the weight fraction of 1:5 H cell boundary phase increases from ~25% to ~37% as well,resulting decreasing of the average Cu content at cell boundaries from 13.59 at% to ~8.52 at%.It is found that the Cu-lean characteristic at cell boundary phase is the reason that gives rise to higher magnetic properties at elevated temperatures for x=0.04 magnet.
基金supported by the National Key R&D Program of China (No.2021YFB3501600)the Key R&D Program of Zhejiang Province (Nos.2021C01191 and 2021C01190).
文摘The excellent thermal stability of magnetic properties of Sm_(2)Co_(17)-based magnets is their most impor-tant feature.However,this stability is reduced when the maximum energy product of Sm_(2)Co_(17)-based magnets is improved,which is mainly determined by the Fe/Cu distribution of the 2:17R cell and 1:5H cell boundary phases.During the demagnetization process,the Cu-rich 1:5H cell boundary phase with a width of 2-15 nm obstructs the motion of the domain walls,yielding coercivity.Herein,we report a micron-scale Cu/Zr-rich and Fe-lean 1:5H-based precipitated phase with a lamellar structure,probably induced by Sm_(2)O_(3) doping.This structure enables the separate regulation of Fe and Cu distribution for Sm_(2)Co_(17)-based magnets with Fe-rich 2:17R cell phases and Cu-rich 1:5H cell boundary phases,consid-erably optimizing the thermal stability of magnetic properties.This discovery can be further developed to produce Sm_(2)Co_(17)-based magnets with high performance and excellent thermal stability of magnetic properties.
