【作者】 王伟；

【导师】 严密；

【作者基本信息】 浙江大学 ， 材料科学与工程， 2007， 硕士

【摘要】 Sendust合金由于具有良好的软磁性能以及低廉的价格，工业上广泛用作磁头和磁芯材料的制造，但是也存在工作温度低、高频性能不佳等缺点。本文在调整合金配方的基础上，采用熔体快淬技术并改变球磨工艺和热处理温度，获得了具有高工作温度和优良高频性能的纳米晶掺Co-Sendust合金。使用快淬法制得了(Fe_1-xCo_x)₈₅Si_9.6Al_5.4（wt％）（x=0，0.05，0.10，0.15，0.20）合金快淬带，经高能球磨获得扁平化程度良好的微粉，球磨粉在氮气保护下退火处理获得了最佳的软磁性能。运用SEM、XRD、VSM和MTG等方法系统研究了经不同工艺处理的样品的微观结构、软磁性能和居里温度。采用复合粘结技术制备了掺Co-Sendust合金／树脂环状材料，运用阻抗分析仪系统测试了不同粉末样品制备的环状样品的高频性能。XRD结果表明，快淬带呈两相结构：在无序α-Fe相的基础上有部分DO₃相析出，Co添加会促使无序相从α-Fe转变为α-Fe（Co）。球磨有利于晶粒的细化，同时也引起了合金内部DO₃相向无序相转变。球磨20h后，DO₃相衍射峰完全消失。使用SEM观察了合金材料的表明形貌，确定具有最佳扁平度的球磨时间为70h；热处理促使球磨粉内部无序α相向有序DO₃相转变，随着热处理温度的升高，材料DO₃相衍射峰越来越明显，长程有序度越来越高。球磨是合金内部应变急剧增大的过程，极大地恶化了材料的软磁性能，矫顽力从8.675 Gs[(Fe_0.85Co_0.15)₈₅Si_9.6Al_5.4合金快淬带]急剧增大到29.099 Gs[(Fe_0.85Co_0.15)₈₅Si_9.6Al_5.4合金磁粉经70h球磨]；退火有利于内应力的消除以及矫顽力的减小，材料的饱和磁感应强度也会有所增加，这主要是由两方面因素引起的：无序相向有序相的转变以及长程有序度的提高。球磨70h，经773K退火30min后的(Fe_0.85Co_0.15)₈₅Si_9.6Al_5.4合金磁粉的饱和磁化强度达到129.8 Am²／kg。更高的退火温度以及更长的保温时间对材料的性能并不会产生太大的影响。Co添加极大地提高了材料的居里温度：当Co含量为0时，材料的居里温度约为740K，而当Co含量增加到0.20时，居里温度上升到1000K。快淬带由于在其厚度与长度方向上晶粒尺寸成分分布不一样，从而引起了不同方向上软磁特性的差异，平行于快淬面的方向上具有更好的软磁性能。系统对比了球磨工艺以及Co含量对Co掺杂Sendust合金高频性能的影响。(Fe_1-xCo_x)₈₅Si_9.6Al_5.4合金磁粉的复数磁导率的实部μ′和虚部μ″在高频范围内都维持一个比较稳定的值，是高频抗电磁干扰的良好基体材料。使用Co含量x=0.15，球磨70h，在773K下退火30min的磁粉制成的同轴圆环样品，其截止频率达到1.154 GHz。球磨70h样品具有最高的截止频率，这主要与样品的扁平化程度有关。更多还原

【Abstract】 Sendust alloy has been used as raw materials to fabricate magnetic heads and cores because of its excellent soft magnetic properties and low prices. However, weak deformability has limited its wider application. In this dissertation, Co doped nanocrystalline Sendust alloy with high working temperature as well as high frequency properties could be prepared while technical parameters and components were changed.(Fe_1-xCo_x)₈₅Si_9.6Al_5.4 （wt%） （x = 0, 0.05, 0.10, 0.15, 0.20） alloy ribbons have been prepared using melt spinning, high energy ball milling has been employed to achieve flakes with large aspect ratio, making sure of its excellent high frequency properties, the ball milled powders were then heat treated under the protection of Nitrogen to get excellent soft magnetic properties. The microstructure, soft magnetic properties and Curie temperature （T_c） of samples with different technical parameters and components were studied systematically using SEM, XRD, VSM and MTG respectively. The annuluses were made from Co-doped Sendust alloy powder mixed with proper epoxide resin and high frequency properties were measured using Impedance Analyzer.X-ray Diffraction has been used to analyze phase composition and structural parameters. As shown that, disordered bcc α-Fe phase and ordered superlattice D0₃ phase have been found in Co free Sendust melt spun ribbons and Co addition made the disordered phase changed from α-Fe to a-Fe（Co）. Ball milling is beneficial for the refinement of grains, meanwhile, it also made phase transformation from ordered DO3 phase to disordered phase happened. The diffraction peaks of DO3 phase disappeared completely while samples were milled for only 20 h. According to the results of SEM, largest aspect ratio could be achieved while the sample was milled for 70 h. The transformation from disordered to ordered phase happened during heat treatment. Accompanied with the increase of heat-treated temperature, the diffraction peaks of D0₃ phase became more and more obvious and long-range order got higher.Internal strain increased greatly at the stage of ball milling and it deteriorated soft magnetic properties a lot, the coercivity increased from 8.675 Gs to 29.099 Gs when (Fe_0.85Co_0.15)₈₅Si_9.66Al_5.4 alloy ribbons were ball milled for 70 h. Heat treatment was beneficial for minimizing the coercivity. Saturation magnetization （M_s） was found to increase duringheat treatment due to the followed two reasons: The transformation from disordered to ordered phase and the increase of long-range order. M_s of 129.8 Am²/kg could be achieved in (Fe_0.85Co_0.15)₈₅Si_9.6Al_5.4 powder when it was heat treated at 773 K for 30 min after ball milling for 70 h. No obvious effects on properties of alloy powder have been found since higher annealing temperature and longer holding time were employed. Curie temperature （T_c） has been greatly improved when Co was added to the sample. T_c of 1000 K could be achieved when x=0.20 while that of Co free sample is only 740 K. Grain size as well as phase composition were distinct in different directions of the melt spun ribbons, introducing the discrimination of soft magnetic properties. Better performance could be achieved along the direction of melt spun ribbons.The impacts of ball milling technics as well as Co content on high frequency properties of Co doped Sendust alloy have been discussed systematically. Relative stable values of μ’ and μ" of (Fe_1-xCo_x)₈₅Si_9.6A_15.4 alloy powder could be achieved near cutoff frequency, indicating a potential application at the range of GHz. Coaxial annuluses of Φ19×Φ10×3 mm have been prepared using the mixed magnetic powder and epoxide resin. The cutoff frequency of magnetic ring made from sample annealed at 773 K is 1.154 GHz. The highest cutoff frequency could be achieved when the samples was milled for 70 h, at which highest aspect . ratio could be achieved.更多还原