热处理工艺对铁基软磁复合材料电磁性能的影响

以磷酸为磷化剂对雾化铁粉进行磷化处理,然后在800 MPa压力下压制成环形生坯,分别在H2、N2和空气气氛下进行热处理,制成软磁复合材料磁芯,研究热处理气氛、热处理温度与时间对磁芯电磁性能的影响。结果表明:铁粉经磷化处理后,表面包覆完整均匀的磷酸盐绝缘层;与H2和N2气氛相比,磁芯压坯在空气气氛下热处理后拥有更高的磁导率和较小的磁损耗;空气气氛下500℃处理30 min是较优的热处理工艺,磁芯最大磁导率达到350,在频率为1 k Hz和饱和磁感1T条件下的磁损耗仅为145 W/kg,进一步延长热处理时间或提高热处理温度,磁导率增加不明显,但电阻率显著降低,导致磁损耗显著增加,软磁性能恶化。     

铁基软磁复合材料成形和热处理工艺研究

采用磷化处理后的还原铁粉,通过压制、热处理获得铁基软磁复合材料(ISMCs),探讨了成形压力和热处理工艺对材料磁导率、磁损耗和频率特性影响。研究结果显示,900 MPa压力获得密度为7.2 g/cm3磁粉芯,振幅磁导率aμ≥100(30～250 kHz),且μa频率稳定性好(变化量≤0.02～0.03/kHz)。经400℃热处理后,aμ超过120(30～250 kHz),提高了20%。热处理温度超过450℃,磁粉芯的磁损耗显著增加、μa急剧下降。损耗分离研究显示,磁损耗增加主要体现在涡流损耗急剧上升。再经TG-DTA分析,磷化铁粉在462℃时出现一个明显的吸热峰,主要是磷酸氢盐发生分解反应,导致绝缘层破坏,进而影响材料的磁性能。     

粉末冶金工艺对纯铁软磁材料性能的影响

利用粉末冶金技术制备纯铁软磁材料,在不同温度和压力下将不同粒径铁粉压制成生坯,并在保护气氛下进行烧结。结果表明:不同粒径铁粉混合有助于压坯密度的增加,适宜的压制温度可以有效地促进粉末流动,避免大尺寸孔洞的形成,优化组织。140℃、800 MPa温压条件下雾化铁粉压坯密度最高可达7.35 g·cm-3。对比常温压制,温压压坯烧结后孔洞分布均匀。烧结体密度随温度的升高而上升,雾化铁粉压坯在1250℃烧结后密度最高可达7.47 g·cm-3。在一定范围内,软磁材料磁性能与密度成正比,混粉压制试样的密度接近理论值,但在混合铁粉中,较细的铁粉夹杂于粗粉中,阻碍磁畴壁移动,造成饱和磁化强度（M_s）偏小、矫顽力（H_c）偏大的现象,M_s为205.51 emu·g-1,Hc为7.9780 Oe。     

工艺参数对注射成形各向异性粘结NdFeB磁体性能的影响

研究了注射温度、模具温度、注射压力及注射速度对注射成形各向异性粘结NdFeB磁体的磁性能及力学性能的影响，并分析了其原因。结果表明：注射温度及模具温度对磁体磁性能影响较大，而注射压力则对磁体的抗压强度影响较大。在最佳的注射参数下，获得了最大磁能积和抗压强度分别为90kJ／m^3及130MPa的高性能粘结磁体。     

高性能Fe-Si软磁粉芯的制备及性能研究

以Fe-6.5Si粉末为基粉、多组分无机氧化物作为粘结剂,通过温压成形、热处理制得Fe-Si软磁粉芯。分别使用扫描电子显微镜、振动磁强计对样品的密度、微观形貌以及磁性能等进行了测试分析。结果表明:粘结剂的含量、温压压力、温压温度对Fe-Si软磁粉芯的性能都会产生影响,在压制温度150℃、压制压力为900MPa时,粘结剂含量为1.5%(质量分数)的Fe-Si生坯密度可以达到6.34g/cm3,经过720℃氩气气氛下热处理后密度可达到6.58g/cm3,饱和磁感应强度为1.26T,矫顽力为0.81 kA·m-1。     

包覆剂和制备工艺对铁基磁粉芯性能的影响

树脂作为包覆剂包覆的铁粉,通过温压、热处理获得磁粉芯软磁复合材料(SMCs)。本文研究了树脂包覆剂含量、二次温压和热处理对在不同的频率下材料的磁导率和磁损耗的影响。结果表明随着测试频率的增加,SMCs的磁损耗是逐渐增加的,磁导率则是先增大后减小;而随着包覆剂含量的增加,磁损耗和磁导率都逐渐降低;包覆剂含量约为1%是完全包覆的临界值。掺入SiO2纳米粉可以明显降低磁损耗。二次温压可以使磁导率具有较好的频率特性,经500℃、1h热处理可以降低磁粉芯的磁损耗。二次加大压力温压可以极大地提高材料的磁导率,最高可达到688.19(f=50Hz,Hm=1200A/m,N1=10,N2=3,ρ=7.56g/cm3)。     

MnZn-FeNi复合烧结软磁材料的烧结过程和性能研究

采用粉末冶金法制备了MnZn-FeNi复合软磁材料,采用排水法、金相显微镜和X射线衍射仪等手段,研究了样品的烧结过程、坯体的致密化、晶粒生长规律、样品的相结构.采用物理性能综合测试仪(PPMS)测定烧结体的磁性能,研究了材料的微观结构和材料软磁性能之间的关系,分析了样品磁性能变化规律.研究表明,样品密度随烧结温度升高而增大,当烧结温度超过1673 K以后,密度变化趋缓.在烧结过程中,影响材料致密性的主要因素为材料中的气孔和晶粒.随烧结温度升高,气孔向晶界和样品表面迁移,并且合并长大,同时,晶粒也发生长大.复合烧结软磁中的FeNi合金和MnZn软磁铁氧体仍保持原有的相结构,在1773 K的较高烧结温度时,软磁铁氧体出现分解,产生了部分杂相.通过优化烧结工艺,复合烧结软磁材料的烧结温度在1573～1673 K范围内时,样品取得了较好的磁性能,其磁性能为初始磁导率μi=1128,饱和磁化强度MMs=4349 kA·m-1.     

粉末注射成形在软磁材料中的应用

介绍了粉末注射成形在粘结软磁、烧结软磁生产中的应用、研究开发状况。指出粉末注射成形是能够实现低成本生产新性能、新功能的磁体制造技术，强调利用注射成形技术实现磁性元器件结构功能一体化设计、制造的优势。     

型砂材质与挤压成形工艺对砂型表面性能的影响

以数字化柔性挤压成形砂块为研究对象,通过设计单因素试验进行了砂型种类、粘结剂质量分数及挤压压力对型腔表面质量影响规律的研究,进而得出高精度树脂砂型挤压成形的最优参数组合。结果显示:无模砂型外部与砂型内部的表面性能存在差异。不同砂型种类的砂型型腔表面性能不同,沙粒的角形系数对砂型型腔表面性能有较大影响。随着砂型挤压力的提高,砂粒之间的距离减小,砂粒并联接触方式增多,砂型在经过切削时,砂型表面产生裂纹的数量及延伸深度大幅减小,砂型型腔表面性能不断提高。随着树脂质量分数的增大,砂粒的包覆厚度增大,从而砂粒的粘结桥增多,砂型强度增加,砂型切削时产生的裂纹数量减小,砂型型腔表面性能不断提高。本文为真实获得砂型表面质量提供了方法,有助于无模铸造精密成形技术的推广。      

交、直流用铁粉基软磁材料

本文介绍了粉末冶金软磁材料的种类和工艺参数对其性能的影响、应用技术要求以及一些应用实例。重点介绍了近几年发展起来的软磁复合材料的性能及其应用。     

Influence of cryogenic temperature on magnetic properties of soft magnetic composites

Abstract

Magnetic properties of Fe based composite materials with different particle sizes under a cryogenic condition have been investigated. Realisation of this venture has been carried out at the liquid nitrogen temperature. Results of energy loss density were obtained from measurements of the static (dc) hysteresis cycles ranging from 0·1 to 1·0 T. In turn, results of power loss density were obtained from measurements of the dynamic (ac) hysteresis cycles ranging from 50 to 1000 Hz and at the maximum flux density of 0·5, 0·8 and 1·0 T. The study confirmed the influence of temperature on magnetic parameters. It has been shown that total power loss density has increased with decreasing temperature. We report changes in a nature of energy loss after immersing specimens made of soft magnetic composites in liquid nitrogen. Measurements of the maximum relative permeability were also conducted.     

Effect of lanthanum content on microstructure and magnetic properties of non-oriented electrical steels

The effect of lanthanum content in the range of 0-0.011 wt.%,on the inclusion size distribution,microstructure,texture and magnetic properties of three non-oriented electrical steels was studied.After final annealing,lanthanum effectively inhibited the precipitation of MnS precipitates in steel,the formations of La2O2S and LaS inclusions not only acted as nuclei of AlN precipitates,but also combined with Al2O3 and formed composite inclusions with larger size.Grain size firstly increased and then decreased with lanthanum content increasing.Steel containing 0.0066 wt.% lanthanum obtained the largest grain size,the strongest {110}<110> texture and the weakest {112}<110> texture among all the tested steels.Magnetic flux density firstly increased and then decreased,core loss firstly dramatically decreased and then slightly decreased with lanthanum content increasing.Among the three tested steels,steel with 0.0066 wt.% lanthanum demonstrated the best comprehensive magnetic properties mainly through the development of favorable texture and appropriate final grain size.     

原始粉料的球磨工艺对Ti/HA生物复合材料性能的影响

采用不同球磨介质对Ti 30％HA配比的粉料进行高能球磨，随后于1000℃氩气气氛中热压，研究了球磨工艺对Ti／HA生物复合材料性能的影响。结果表明：随着球磨时间的延长，复合材料的致密度略有下降，硬度上升。热压后，Ti基体形成连通的网络，HA弥散分布其中。干磨工艺条件下，球磨时间越长，显微组织越细；湿磨工艺条件下，较短的球磨时间，即可达到较好的细化弥散效果。因此，采用高能球磨，可使Ti／HA生物复合材料在较低的温度下致密化，同时，湿磨介质的存在，有利于在短时间内得到力学性能和生物活性都较好的Ti/HA生物复合材料。     

Effect of niobium on glass-formation ability and soft magnetic properties of Gd-doping glassy alloys

The effect of niobium on glass-formation ability and soft magnetic properties were studied in Fe-Gd-B glassy alloys. The glassy alloys exhibited high glass-formation ability when the element of Nb was added. Bulk glassy rod （Fe0.87Co0.13）68.5Gd3.5Nb3B25 with a diameter up to 3 mm was produced by copper mold casting. The size of the atom might play an important role in increasing glass-formation ability. The coercive force of glassy （Fe0.87Co0.13）71.5.xGd3.sNbxB25 （x=1.2, 1.5, 2, 2.5, 3, 4） alloys decreased after the addition of niobium element and was in the range of 1.5-2.9 A/m. The permeability spectrum of （Fe0.87Co0.13）70.3Gd3.5Nb1.5B25 glassy ribbon showed that the relaxation frequency （f0） was 6.1 MHz.     

Microstructural modelling of electrical conductivity and mechanical properties of sintered ferrous materials

Abstract

The role of microstructure on mechanical properties of sintered ferrous materials was studied using a method based on electrical conductivity measurement. The method was accompanied by quantitative fractography to evaluate the dewaxing and sintering process in iron compacts. The effects of manufacturing parameters, such as compacting pressure in the range of 150–800 MPa, sintering temperature from 400 to 1300°C, sintering time up to 8 h, and lubrication mode were investigated. Several mathematical models were checked to obtain the best one for prediction of electrical conductivity changes as a function of manufacturing parameters. The mechanical properties of the sintered compacts were also evaluated to establish a relationship between conductivity, total porosity, pore morphology, and mechanical behaviour. The results show that the electrical conductivity/resistivity of sintered materials is closely related to its microstructure, so that measuring these properties can replace destructive test methods for prediction of mechanical strength of sintered materials with homogeneous matrix microstructure. The application of the method is shown for sintered Fe, Fe–0·8%C, and Fe–1·5%Mo–0·7%C compacts.