退火温度对汽车用Fe-Cr-Mo合金组织及阻尼性能的影响

以高阻尼汽车用Fe-Cr-Mo合金为对象,研究了不同退火温度对其组织和阻尼性能的影响规律。结果表明,随着磁场强度的增加,合金的磁致伸缩系数先增加然后趋于稳定;当退火温度为900℃,合金的磁致伸缩系数最高;随着退火温度的升高,合金的损耗因子先增加后降低,在退火温度为900℃时取得最大值;合金经充分的退火后,饱和磁致伸缩系数与最大阻尼值成正比关系。     

多Terfenol—D棒磁致伸缩作动器结构优化设计

设计了一种包含3根Terfenol-D棒的磁致伸缩作动器,并根据电磁学原理,在对磁致伸缩作动器内部磁路分析的基础上推导出了作动器输出位移与Terfenol-D棒的长度以及上下端盖的尺寸之间的关系,以此为根据对作动器进行结构优化以使其结构更加紧凑.通过ANSYS仿真表明:由于螺线管和上下端盖组成了闭合磁路,大大改善了螺线管端部的磁场分布情况,同时由于采用热膨胀抵消补偿法克服了温度对作动器输出位移的影响,从而最大限度地消除了作动器输出的非线性.     

超磁致伸缩微驱动车削刀架及其可行性研究

针对现有的超磁致伸缩微驱动的车削刀架存在输出位移小、稳定性差等问题,设计一种应用于主动控制车削颤振车削刀架的新型超磁致伸缩驱动器(GMA)。基于ANSYS仿真软件探究开闭合磁路状态下GMM棒磁场强度以及分布情况,并搭建GMA动态位移特性测试系统研究电流频率和预压力大小对GMA输出特性的影响。研究结果表明：闭合磁路状态通过GMM棒的平均磁场强度更高且均匀性较好;在预压力一定时,GMA的动态输出位移峰峰值与输入电流频率呈负相关;在预压力为300 N时,GMA的动态输出位移峰峰值达到最大值为45μm。仿真和实验结果说明所提出的新型GMA可以稳定输出动态位移,满足主动控制车削颤振的激励频率及最大动态输出位移的需要,所设计的超磁致伸缩微驱动车削刀架是完全可行的。     

超磁致伸缩驱动器及其微位移特性研究

基于超磁致伸缩材料的磁致伸缩效应,研制一种具有可控微位移功能的超磁致伸缩驱动器,并对外加预压力下该驱动器的微位移特性进行了实验研究。采用位移传感器、数据采集卡、驱动电源等,搭建超磁致伸缩驱动器的微位移性能测试台,实验研究在外加电流、预压力下,超磁致伸缩驱动器的输出位移与外加电流的关系。研究结果表明:在外加预压力为0~300 N时,驱动器的输出位移随外加电流的增加而增加;而在外加预压力为300~400 N时,超磁致伸缩驱动器的输出位移随输入电流的增大而减小。     

Tb_xDy_(1-x)(Fe_(0.6)Co_(0.4))_2合金的磁性和磁致伸缩性能

利用电弧熔炼法制备Tb_xDy_(1-x)(Fe_(0.6)Co_(0.4))_2合金(0.27≤x≤0.40),对合金的磁性和磁致伸缩性能进行研究。利用XRD、交流初始磁化率测试仪、超导量子干涉仪和标准应变测试仪,对样品的物相组成、居里温度、磁化曲线和磁致伸缩性能进行表征。结果表明:当x≤0.27时合金的易磁化方向为á100?方向,当x≥0.30时合金的易磁化方向变为〈 111〉方向;合金的居里温度随x的增加而增加;x=0.32附近时合金的磁晶各向异性常数K_1有极小值,室温时合金在x=0.32附近时达到各向异性补偿;当x=0.32时饱和磁致伸缩系数达到9.57×10~(-4);随Co含量的增加,合金的各向异性补偿点向Tb含量高的方向移动。Tb_(0.32)Dy_(0.68)(Fe_(0.6)Co(0.4))_2合金具有高磁致伸缩系数和低各向异性,是一种实用的磁致伸缩候选材料。     

退火磁场施加方式对Tb0.3Dy0.7Fe1.95合金磁伸性能的影响

研究了磁场退火时磁场施加方式对《110》取向Tb0.3Dy0.7Fe1.95定向凝固多晶合金磁致伸缩性能的影响.退火磁场强度为1T,保温时间30 min.研究表明,在623K下采用垂直磁场且冷却时保持磁场的方式退火,可改善综合磁伸性能,如提高饱和磁致伸缩系数并使低场磁致伸缩系数基本不变,提高最大动态磁致伸缩系数且其对应的磁场基本不变.冷却阶段撤去磁场会减弱磁场退火的作用,而平行磁场退火的效果与垂直磁场相反.     

电液伺服阀用超磁致伸缩转换器的建模与动态仿真研究

介绍电液伺服阀用超磁致伸缩转换器(GMA)的结构和工作原理;在建立转换器数学模型的基础上,构建转换器的AMESim仿真模型,分析阻尼系数、等效质量、驱动频率和GMM棒刚度系数等不同参数对转换器动态特性和输出位移的影响。仿真结果表明:增大阻尼系数,减小等效质量,可以提高转换器的动态特性;减小驱动频率和GMM棒刚度系数,可以增加转换器的输出位移。仿真结果为电液伺服阀用超磁致伸缩转换器的结构参数优化提供了理论依据。     

粉末冶金粘结磁致伸缩材料

粘结磁致伸缩材料是由Terfenol-D粉末与树脂粘结剂混合固化而成。TbDyFe粉末颗粒的大小,树脂的粘度系数,树脂的配比及磁场中的取向都对粘结磁致伸缩材料的磁致伸缩性能产生较大的影响。试验结果表明,TbDyFe粉末颗粒尺寸的大小对粘结磁致伸缩材料的磁致伸缩性能影响较大。制造较好性能的粘结磁致伸缩材料所需TbDyFe粉末颗粒尺寸应控制在＜280μm。同时,材料在压型过程中由于外加磁场而使磁畴取向,从而提高了磁致伸缩性能。     

相变温控及其在超磁致伸缩致动器中的应用

文章分析了超磁致伸缩致动器的热特性,提出了采用相变材料控制超磁致伸缩棒温升的抑制方法。试验结果表明相变温控装置能将超磁致伸缩棒的温度控制在45±0．5℃,此时因工作温度变化引起的位移输出误差不超过0．1μm,超磁致伸缩致动器相应的输出精度达到0．5μm。     

磁致伸缩性能测试系统的研制

磁致伸缩材料的磁致伸缩系数值与磁场强度大小、温度和材料种类等有关。介绍了磁场强度、磁致伸缩系数和测试环境温度的计算机测量与控制系统。其中包括硬件的组成与配置，软件的编制与调试及测试结果的分析。     

Magneto-thermo-mechanical characterization of giant magnetostrictive materials

The variations of magnetization and magnetostriction with temperature and stress were investigated through the analysis of the effective field,induced by temperature and stress.A nonlinear magnetostrictive model of giant magnetostrictive materials was proposed.The proposed model can be used to calculate the magnetostrictive characterization of giant magnetostrictive materials in different temperatures and under different stresses.The coupling effects of axial stress,magnetic field,and temperature on the magnetostriction of a Terfenol-D rod were numerically simulated as well as experimentally tested.Comparison between the calculating and experimental results shows that the proposed model can better describe the magneto-thermo-mechanical characteristics of Terfenol-D rod under different temperatures and compressive stress.Therefore,the proposed model possesses an important significance for the design of magnetostrictive devices.     

Effects of high temperature annealing on the chemical homogeneity and Magnetostriction of Tb0.3Dy0.7Fe1.90 Intermetallic Compound

A rare earth-iron intermetallic compound Tb_0.3Dy_0.7Fe_1.90, also called Terfenol-D, has a gigantic room temperature magnetostriction at a relatively small magnetic field. In this study microsegregation of Tb and Dy in directionally solidified Terfenol-D was investigated. It was predicted from a calculated phase diagram and experimentally verified that Tb concentration at the center of the cell which solidified earlier was lower than that at the cell boundary. In order to homogenize this microsegregation, specimens were annealed at 1000°C for 40 hours, and various magnetic properties were measured as a function of applied field under uniaxial compressive stress in the range from 0.5 to 1.2 MPa. After the annealing, the maximum magnetostriction increased at a compressive stress below 9 MPa, magnetostrictive coefficient d₃₃ and magneto-elastic coupling coefficient k₃₃ increased, but permeability decreased. These results may be due to the reduction of magnetocrystalline energy which was locally very high before annealing due to microsegregation.     

Bonded Terfenol-D composites with low eddy current loss and high magnetostriction

Bonded Terfenol-D composites,with high electrical resistivity and low eddy current loss,can be used in an alternating magnetic field with high frequency.However,the nonmagnetic binder impairs the magnetostriction of the composites.To achieve high magnetostriction and low eddy current loss,the mixture of the alloy powder and binder was compressed at low pressure in an oriented magnetic field.After this,the aligned samples were recompressed by cold isostatic pressing(CIP).Besides,the effect of particle size on the magnetostriction of the bonded Terfenol-D composites was also studied.The results showed that the bonded Terfenol-D composites had excellent magnetostriction when the particle size was 50-80 μm.The oriented magnetic field and CIP could improve the magnetostriction of the bonded composites,which reaches 1020×10-6.The bonded Terfenol-D composites had good compact structure and high density(7.24 g/cm3).The magnetic loss of the bonded Terfenol-D composites was 192 mW/cm3 at a frequency of 100 kHz in a magnetic field of 960 A/m,which was about one third of that of casting Terfenol-D alloys.     

退火对非晶合金磁特性及铁心磁致振动的影响

为研究退火处理对非晶合金磁特性及非晶铁心振动的影响,采用磁特性测量设备对退火前非晶带材及退火后非晶铁心的磁化特性和磁致伸缩特性进行了测量,基于测量数据建立了非晶合金卷形铁心磁-机械多物理场耦合模型,计算得出退火前后两种状态铁心各处的磁通密度分布及振动情况,并与样机振动测量数据进行了比较。结果表明:退火可提高非晶合金饱和磁感应强度,改善磁导率,并可减小磁致伸缩系数,从而有效地抑制变压器铁心的振动。     

气体雾化制备Fe-Ga合金粉末的微结构及磁致伸缩性能

为改善Fe-Ga合金的高频特性,采用黏结工艺制备Fe-Ga磁致伸缩复合材料.探索采用气体雾化法制备Fe_(81)Ga_(19)合金粉末,利用EDS,SEM,XRD和DTA研究粉末颗粒的基本特性.结果表明,雾化粉末颗粒球形度好,成分与目标成分接近,大部分颗粒内部为多晶体,颗粒以A2相为主,且含有少量DO_3相;经800℃热处理后,颗粒中有大量L1_2相析出,保温8 h,炉冷样品含有大量单晶颗粒.利用Fe_(81)Ga_(19)合金粉末和黏结剂制备黏结复合材料,粒径<25μm的热处理粉末颗粒制备黏结样品的饱和磁致伸缩值最大,为6.4×10~(-5).     

Tb-Dy-Fe-Co合金本征磁致伸缩性能

研究了Tb_0.36Dy_0.64(Fe_0.85Co_0.15)_1.95合金中替换元素Co的分布及其对材料内禀磁性和本征磁致伸缩性能的影响. EDS分析表明, 合金中产生了Co富集的富稀土相, Co在其中的含量为21.18%(原子分数), 高于基体中Co的含量9.36%. Co元素部分替换Fe未改变巨磁致伸缩合金主相Laves相的结构, 合金的Curie温度从378℃提高到420℃, 拓展了应用温度范围; 同时, Co元素的添加部分补偿了由于Tb/Dy比例提高所增大的磁晶各向异性, 有利于改善合金低场性能. 为避免样品的生长取向对本征磁致伸缩性能测量的影响, 保证测量结果的准确性, 制备了 Tb_0.36Dy_0.64(Fe_0.85Co_0.15)_1.95无取向等轴晶样品, 测量了合金的饱和磁致伸缩常数 λ_s. 通过Laves相XRD谱中(440)峰的劈裂, 计算了沿<111>方向上的磁致伸缩λ₁₁₁, 由此计算出沿<100>方向上的磁致伸缩λ₁₀₀. 与Tb_0.3Dy_0.7Fe_1.95合金相比, Co添加后λ₁₁₁稍有降低, λ₁₀₀得到显著提升, 饱和磁致伸缩常数λ_s基本相当.     

Effect of fabrication parameters on the microstructure,in-plane anisotropy and magnetostriction of Fe-Ga thin films

The microstructure,in-plane anisotropy,and magnetic properties of Fe-Ga thin films were investigated by X-ray diffraction analysis,vibrating sample magnetometer,and capacitive cantilever method.The in-plane induced anisotropy is well formed by the applied magnetic field during sputtering,and the anisotropy field Hk decreases with the sputtering power increasing.The coercivity of Fe-Ga thin films decreases with increasing power when the sputtering power is less than 60 W and increases when the power is larger than 60 W.The magnetostriction of the thin films reaches 66 × 10-6 at the sputtering power of 60 W.Excellent Fe-Ga films,which exhibit good field sensitivity,low coercivity and high magnetostriction,have been fabricated at the power of 60 W,and they can be used as the materials of magnetostrictive transducers.     

功率对磁控溅射TbDyFe薄膜磁致伸缩性能的影响

采用直流磁控溅射工艺制备TbDyFe磁致伸缩薄膜，通过考察薄膜成分及其微结构，分析研究了溅射功率对薄膜磁致伸缩性能的影响。结果表明，同一薄膜内部成分相当均一，但不同溅射功率条件下的薄膜成分相异。溅射功率较低，薄膜内部微柱状体结构导致了磁各向异性的产生，磁致伸缩性能下降；溅射功率提高到120W，微柱状体结构消失，薄膜内部趋于均一连续，磁致伸缩性能较好。     

In situ dynamical control of the strain and magnetoresistance of La0.7Ca0.15Sr0.15MnO3 thin films using the magnetostriction of Terfenol-D alloy

We fabricated a magnetoelectric laminate structure consisting of a magnetostrictive Tb_0.3Dy_0.7Fe_1.92 (Terfenol-D) plate bonded to a La_0.7Ca_0.15Sr_0.15MnO₃ (LCSMO)/0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (PMN-PT) structure where a LCSMO film was epitaxially grown on a PMN-PT single crystal substrate. When a dc magnetic field is applied perpendicular to the film plane, the magnetoresistance of the LCSMO film in the paramagnetic (ferromagnetic) state for the LCSMO/PMN-PT/Terfenol-D structure is larger (smaller) than that for the LCSMO/PMN-PT structure without Terfenol-D. These effects are caused by the magnetostriction-induced in-plane compressive strain in the Terfenol-D, which are transferred to the PMN-PT substrate, leading to a reduction in the in-plane tensile strain of the epitaxial LCSMO film and thereby modifying the magnetoresistance of the film.     

Effect of the magnetic state on the damping properties of iron and nickel alloys

The dependences of the ΔEeffect and internal friction on the magnetic field have been investigated upon the magnetization and magnetization reversal of some polycrystalline ferromagnetic materials with different properties. It has been shown that for all the materials that have been investigated there is characteristic a nonmonotonic dependence of the magnitude of internal friction on the magnetic field both for the magnetization curves and for the major hysteresis loops. It is shown that in the sonic frequency range of elastic vibrations the basic mechanism of the formation of the magnetic peaks of internal friction in the materials investigated is magnetostrictive; the damping depends simultaneously on the instantaneous values of magnetostriction and magnetostrictive sensitivity.