高饱和磁感Fe82Si3.8B13.9C0.3非晶铁芯的退火及浸漆工艺

研究了不同磁场退火和浸漆固化工艺对Fe₈₂Si_3.8B_13.9C_0.3非晶合金环形铁芯损耗和磁性能的影响,并与1K101合金铁芯进行了对比。结果表明:与1K101合金相比,Fe₈₂Si_3.8B_13.9C_0.3合金铁芯的最佳退火温度低于1K101合金,其中纵磁退火时达到最低,为330 ℃。纵磁退火Fe₈₂Si_3.8B_13.9C_0.3合金铁芯有着更高的饱和磁感应强度,B_{3500 A/m}=1.611 T。经350 ℃无磁场退火处理后,Fe₈₂Si_3.8B_13.9C_0.3合金铁芯的损耗P_{50 Hz, 1.4 T}=0.360 W/kg,稍高于1K101合金;经330 ℃纵磁退火处理后,Fe₈₂Si_3.8B_13.9C_0.3合金铁芯的损耗P_{50 Hz, 1.4 T}=0.257 W/kg,也高于1K101合金;经350 ℃横磁退火处理后损耗P_{50 Hz, 1.4 T}=0.163 W/kg,低于1K101合金。纵磁退火Fe₈₂Si_3.8B_13.9C_0.3合金铁芯经浸漆固化处理后,磁通密度B_{800 A/m}=1.341 T,比纵磁退火1K101合金浸漆固化铁芯高15%;纵磁退火且浸漆的Fe₈₂Si_3.8B_13.9C_0.3合金铁芯损耗低于1K101合金浸漆铁芯,且随着频率升高优势更加明显;当频率大于1000 Hz时,纵磁退火且浸漆的Fe₈₂Si_3.8B_13.9C_0.3合金铁芯的损耗值低于未浸漆铁芯。     

FeCoNiSiB非晶合金感生各向异性对磁性能的影响

研究了恒温张力退火和横磁退火工艺对FeCoNiSiB非晶合金各向异性及磁性能的影响。结果表明,合金经恒温张力退火后表现出高直流偏置性能和高损耗的特点,而经横磁退火后具有优异的综合软磁性能,即具有高直流偏置能力的同时具有低损耗的特点。其中,恒温张力退火过程中提高退火温度时合金直流偏置能力增加,550 ℃下张力退火5 min的直流偏置场强度H_0.98为195 A/m,对应的损耗值P_cm为7255 W/kg;而经450 ℃横磁退火后,合金直流偏置场强度H_0.98可达374 A/m,对应的损耗值P_cm仅为200 W/kg。除此之外,经恒温张力退火和横磁退火后FeCoNiSiB非晶合金内部均形成180°条形磁畴结构,但其磁化矢量方向分别平行和垂直于磁化方向。     

热处理对水雾化Fe74Cr2Mo2Sn2P10C2Si4B4非晶磁粉芯性能的影响

采用水雾化Fe74Cr2Mo2Sn2P10C2Si4B4非晶磁粉制备出了高频特性较好的磁粉芯。研究了去应力退火和磁场退火对磁粉芯磁性能的影响。结果表明:非晶磁粉芯压制后的去应力退火处理能有效提高磁导率和品质因数。过高热处理温度使非晶粉末晶化,析出导电性较差的非铁磁相,恶化磁性能。最佳退火温度为400℃,最佳的磁性能为:在3500 kHz的频率下,μ=40.5,Q=225。磁场退火对Fe74Cr2Mo2Sn2P10C2Si4B4非晶磁粉芯磁导率影响较小。纵向磁场退火能增大非晶磁粉芯的损耗,横向磁场退火能降低非晶磁粉芯的损耗,磁粉芯总损耗变化主要来源于磁滞损耗。     

分步纵磁热处理对Fe3.85Co66.18Si14.5Ni0.97B14.5钴基非晶合金结构和性能的调控

为了制备低磁导率、高矩形比、低矫顽力的钴基非晶合金,对Fe_3.85Co_66.18Si_14.5Ni_0.97B_14.5非晶合金带材采用施加不同热处理工艺,且对其结构和性能进行测试分析的方式进行调控。结果表明,分步纵磁热处理之后的磁芯弛豫焓降低,致密度和有序度增加;在晶化温度之下进行退火的合金都保持非晶态;分步纵向磁场热处理可显著提升磁芯的磁学性能,且当普通热处理温度为480 ℃时,性能最佳,矫顽力0.17 A/m、矩形比96.81 %、1 kHz的有效磁导率为5675.05,且此时的磁畴呈规则的板条状,取向与外磁场呈12.8°的夹角。基于Bertitto模型对其进行损耗分离,发现满足公式P_v=11.05×f×B^0.9814_m+0.7495×f²×B²_m。     

磁场处理时间对铁基纳米晶磁芯磁性能的影响

使用厚度为16～18μm的Fe_73.5Cu₁Nb₃Si_15.5B₇纳米晶带材,卷绕成47 mm×27 mm×15 mm的纳米晶环形磁芯。除合金成分外,退火工艺也直接影响磁芯性能。退火过程中的磁场时间是影响磁性能的关键因素之一。随着延长施加磁场时间,初始磁导率μ_i和最大磁导率μ_m呈现单调递减的趋势;剩磁B_r和矩形比B_r/B_s也呈现单调递减趋势;矫顽力H_c呈现单调递增的趋势。磁导率μ拐点向高频方向移动,说明在相同磁场处理温度下,延长磁场处理时间,有利于磁芯高频磁导率的提高,而且随着磁场处理时间延长,损耗、抗直流偏置能力以及在ESD试验中的稳定性也有比较明显的提高。     

罩式退火工艺的升温速率对无取向硅钢织构及性能的影响

研究了罩式退火工艺的升温速率对0.8%Si无取向硅钢组织、织构及磁性能的影响。结果表明,经过不同升温速率退火后,无取向硅钢的再结晶织构主要为{111}织构,伴随有{110}、{100}织构。随着退火升温速率的提高,晶粒尺寸逐渐增大,{111}织构明显减弱,{110}织构明显增强,{100}织构没有明显变化,铁损P_1.5/50逐渐降低,磁感应强度B₅₀₀₀逐渐增强。但当升温速率由80 ℃/h升高至100 ℃/h时,{111}织构出现一定程度的增强,{110}织构出现减弱,{100}织构没有明显变化,铁损P_1.5/50增大,磁感应强度B₅₀₀₀减小。在退火升温速率为80 ℃/h时,无取向硅钢可获得最优的磁性能:P_1.5/50=4.249 W/kg,B₅₀₀₀=1.715 T。     

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 研究了不同的磁场退火方式对非晶合金铁芯磁性能的影响。结果表明,纵向磁场退火后非晶合金铁芯的剩磁、最大磁导率和损耗增加;横向磁场处理后非晶合金铁芯的剩磁、最大磁导率、损耗和矫顽力减小;先加横向磁场后加纵向磁场退火,非晶合金铁芯可同时获得高的剩磁和低的损耗。     

纵向磁场退火处理对Fe73.7Si15.3Cu1Nb3B7合金组织结构和性能的影响

研究了纵向磁场不同温度退火处理对组成为Fe_73.7Si_15.3Cu₁Nb₃B₇的1k107B纳米晶合金带材的组织结构和软磁性能的影响。结果表明：在纵向加磁电流为150 A、退火温度区间为525～595℃时,合金的矩形比均在0.97以上,晶粒尺寸(D)和矫顽力(H_c)小幅度增加,最大磁导率(μ_m)则与之相反,损耗(P_s)在575℃时取得最小值(99 W/kg@50 kHz, 0.4 T);有效磁导率(μ_e)随着退火温度的升高呈先增加后减小的趋势;通过磁光克尔显微镜观察到纵向磁场退火后合金内部形成规则的平行于磁场方向的条纹畴,且随着退火温度的升高磁畴壁厚度逐渐增大。     

磁场热处理对铁基纳米晶合金磁性能的影响

研究了不同条件的磁场热处理工艺对铁基纳米晶带材磁性能的影响。研究结果表明,铁基纳米晶材料在0~10kHz范围内,其磁导率随施加磁场的温度降低而迅速升高,而在10kHz以上的频段,其磁导率随施加磁场温度的变化较小。与普通热处理的结果相比,在400℃以下施加磁场可以提高材料0~50kHz范围内的磁导率,而在400℃以上施加磁场却可以压低材料0~50kHz范围内的磁导率,并且施加磁场后均能提高材料在50kHz以上的磁导率。     

退火处理对温压Fe78Si9B13非晶软磁粉芯的影响

采用粉末冶金温压成形技术研制了Fe₇₈Si₉B₁₃非晶软磁粉芯,研究了退火处理对该种软磁粉芯的密度、磁导率、磁损耗、品质因数的作用。结果表明,当退火温度为450 ℃及以上时,磁粉芯已被晶化。在25~400 ℃范围内,有效磁导率随温度升高而迅速增大,400 ℃时达到最高值33.9（100 kHz）,随后急剧下降。随着退火的温度升高,磁粉芯的磁损耗逐渐减小,400 ℃退火时磁损耗达到最低值82.52 W/kg（100 kHz),然后会随退火温度升高迅速增大。磁损耗经退火后明显比未退火的小。品质因数随退火温度的变化趋势与磁损耗的刚好相反。磁场退火比未加磁场的退火更有利于提高磁粉芯的磁导率和降低磁损耗。     

DT4E电磁纯铁真空退火磁性能不合格的分析和改进

某DT4E电磁纯铁零件真空退火后存在矫顽力超出设计要求的问题。针对此问题,对DT4E电磁纯铁进行了860～1150℃×4 h真空退火处理,研究了退火温度、磁性能测试试环尺寸以及原材料中杂质成分对其磁性能的影响。结果表明,随着退火温度的升高,磁感应强度B₂₅₀₀的变化呈“M”型,矫顽力H_c呈“V”型变化,最大磁导率μ_m与矫顽力H_c的变化趋势相反。最佳的真空退火温度为900℃,此时磁感应强度B₂₅₀₀为1.63 T,矫顽力H_c为25.19 A/m,最大磁导率μ_m为23.64 mH/m,满足设计要求,且磁环试件的规格尺寸对DT4E电磁纯铁磁性能的测量结果没有明显影响。原材料中杂质元素的含量对磁性能影响较大,当C含量较高时,磁导率下降,矫顽力升高,容易导致磁性能不合格。     

Anion gap and stability of the metallic phase for (TMTSF)2ClO4

Starting with the prototype nesting spectrum of (TMTSF)₂PF₆, it is emphasized that the gap due to anion ordering (AO) would result in a somewhat different SDW state for ClO₄ if the 'antinesting' term, t_b^′ was omitted. The field then first diminishes that term, improving nesting. At the same time the field decreases pairing between subbands with nesting features because of the difference in the symmetry of their wavefunctions. This leads to the reentrance of the metallic state. The magnetic breakdown (MB) gradually decreases the effect of AO. Properties of the "prototype" PF₆-material are expected to be seen again at large magnetic fields. However, it occurs in a peculiar phase diagram with sharp spikes in T_SDW periodic in the inverse magnetic field, 1/H. Cyclotron resonance on open orbits is discussed to study whether the 'transverse' gap due to AO in (TMTSF)₂ ClO₄ manifests itself in other properties.     

On the synthesis and characterization of a new manganite type CMR material: La0.7Hg0.3MnO3

A new manganite type CMR material, La_0.7Hg_0.3MnO₃ has been successfully synthesized and has been found to exhibit magnetoresistance (≈9%) at low fields (≈1.5 kG). The synthesis has been carried out through a solid state reaction route consisting of the formation of La_0.7MnO₃ followed by diffusion of Hg leading to La_0.7Hg_0.3MnO₃. The as grown samples are polycrystalline and correspond to an orthorhombic unit cell with the lattice parameters; a=5.5183 Å, b=5.6383 Å and c=7.5368 Å. The typical grain size as revealed by scanning electron microscopy is in the range of 0.5–2 μm. The ρ–T behaviour shows a peak at T_IM=227 K. The ρ–T behaviour above this temperature corresponds to that of an insulator and below this to that of a metal. The ρ–T behaviour remains unaltered when a magnetic field (H_dc=1.5 kG) is applied. However, with this magnetic field a drop in the resistivity is observed up to 77 K. At room temperature the magnetoresistance ratio (MRR) is too small but it steadily increases as the temperature is decreased. Thus, MRRs at 227.13 and 77 K are 3.41 and 9.05%, respectively, in an applied field of H_dc=1.5 kG. At a given temperature the variation in MRR with field H_dc is rapid at lower field values (H_dc<1.2 kG) and scales linearly for higher field values (H_dc>1.2 kG). It may be mentioned that the present work on the synthesis and magnetoresistance behaviour of La_0.7Hg_0.3MnO₃, is the first of its type.     

热等静压对铁基非晶纳米晶合金软磁性能的影响

在铁基非晶纳米晶合金,普通氮气热处理最佳退火温度的基础上,将热等静压工艺引入到非晶带材磁芯的退火工艺中,探究热等静压工艺对Fe基非晶纳米晶合金软磁性能的影响。用X射线衍射仪、精密磁性元件测试仪和软磁交流设备测量了铁基非晶带材的晶体结构、磁芯的电感L和磁损耗P_s等。结果表明,在频率100 kHz和工作磁感应强度B_m=0.1 T时,普通氮气保护退火样品的矫顽力和磁损耗为2.04 A/m、10.10 W/kg,而热等静压样品则为1.33 A/m、6.58 W/kg,分别降低了53.4%、34.9%;普通氮气保护退火样品的有效磁导率和品质因数为11 579、0.46,而热等静压则为15 980、0.70,分别增加了38.0%、52.2%。     

薄带连铸3.4%Si无取向硅钢的组织、织构演变及性能

基于薄带连铸技术,采用单阶段冷轧和两阶段冷轧工艺分别制备了0.35 mm和0.20 mm高牌号无取向硅钢,利用EBSD、XRD等检测手段分析了无取向硅钢制备全流程的组织和织构演变。研究表明,薄带连铸制备的铸带以粗大柱状晶为主,且具有较强λ纤维织构,取向密度达到4.76,无γ织构。正火处理后部分等轴晶粒长大,织构类型没有明显变化。单阶段冷轧板以α织构为主,经退火后再结晶织构以均匀λ织构和γ织构为主,强点为{001}<120>,取向密度为5.41。两阶段冷轧板以λ织构和γ织构为主,剪切变形明显。再结晶退火后组织相对粗大,且形成了较强的Cube织构,取向密度为6.45。得益于初始有利织构的遗传,试验钢具有高磁感、较高强度优势,且铁损值达到常规流程相当水平。0.35 mm退火板B₅₀达到1.77 T,P_1.0/400为20.78 W/kg。0.20 mm退火板B₅₀为1.70 T,P_1.0/400达到13.74 W/kg,高频铁损优势明显。两种规格无取向硅钢屈服强度均超过415 MPa,伸长率超过15%。     

Finished surface morphology,microstructure and magnetic properties of selective laser melted Fe-50wt% Ni permalloy

This work focuses on the structure and magnetic properties of Fe-50wt% Ni permalloy manufactured from the pre-alloyed powder by selective laser melting (SLM). The selective laser melted (SLMed) alloys were characterized by a 3D profilometer,optical microscope, scanning electron microscope, X-ray diffraction, etc. The effects of the volume energy density of laser(LVED) on structure, and magnetic properties with coercivity ( H _c ), remanence ( B _r ), and power losses ( P     

Influence of A-site cation size-disorder on structural, magnetic and magnetocaloric properties of La0.7Ca0.3−xKxMnO3 compounds

The structural and magnetic properties of perovskite oxides La_0.7Ca_0.3−xK_xMnO₃ (0 ≤ x ≤ 0.15) have been investigated to explore the influence of the A-site cation size-disorder (σ²). The materials were prepared by the solid-state method and then characterized by X-ray diffraction (XRD). The XRD data have been analyzed by Rietveld refinement technique. For K doping concentration x ≤ 0.075, the samples crystallize in the orthorhombic structure, while for x ≥ 0.1, the structure becomes rhombohedral. The variation of the magnetization M as a function of the applied magnetic field μ₀H reveals the presence of a structural distortion leading to a reduction of the magnetization at low μ₀H values. When increasing μ₀H, the structural distortion decreases and for a high applied magnetic field, the M (μ₀H) curves saturate indicating the disappearance of the structural distortion. The influence of K doping concentration and the applied magnetic field on the magnetocaloric properties has been considered. A large magnetic-entropy change (|ΔS_M|  5 J/kg K) is obtained in all samples at Curie temperatures between 270 and 280 K for an applied magnetic field of 3 T. These results show that these materials can be used as candidates for magnetic refrigerants near room temperature.