Magnetic properties and resistivity of a 2:17-type SmCo magnet doped with ZrO_(2)

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.

17型车钩装配体有限元分析

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。

17型车钩常见故障浅析

对检修17型车钩过程中发现的故障进行了调查、统计及分析,并提出了改进建议。

17型车钩托架结构优化及虚拟装配

在对煤运火车17型车钩检测时,由于车钩与托架的安装误差,造成了17型车钩检测数据不准确和自动化设备无法找正车钩等问题。为此,从17型车钩与托架安装后的检测精度影响因素入手,运用控制变量法和MATLAB等软件对误差进行分析,指出托架在不同自由度对17型车钩检测结果的影响程度,提出对托架进行结构优化。最后进行17型车钩和托架的虚拟装配试验,结果显示结构优化后的托架与17型车钩装配后安装误差减小,方便自动化设备的应用。

17号锻造钩尾框浅表裂纹扩展特性分析和剩余寿命预测

针对钩尾框裂纹大多为深度较小,长度较长的浅表裂纹的情况,对17号锻造钩尾框的浅表面裂纹扩展进行有限元模拟。分析了表面裂纹在扩展过程中的形状变化,并对具有不同初始长度和初始深度浅表裂纹的钩尾框剩余寿命进行了预测。结果表明,钩尾框椭圆表面裂纹在扩展过程中会发生形状改变,趋于狭长。对深度0.5 mm和1 mm,不同长度的初始浅表裂纹钩尾框剩余寿命模拟表明锻造钩尾框具有较高的抗断裂性能。对于相同初始长度与深度的裂纹,中间裂纹较之边角裂纹更危险。基于模拟结果,得到了不同初始长度的中间裂纹和边角裂纹的钩尾框剩余寿命预测公式。

基于多体动力学的17型车钩防跳性能研究

以17型车钩装配体为研究对象,分析了车钩的防跳原理,采用多体动力学仿真软件Recurdyn对其进行建模和仿真实验.在仿真软件中施加纵向、垂向及其耦合的加速度冲击,以锁铁能否达到开锁位为评价指标,针对设计尺寸与磨耗到限对应的无防跳插销+无复位弹簧、无防跳插销+有复位弹簧、有防跳插销+无复位弹簧和有防跳插销+有复位弹簧四种工况,对该型车钩的防跳可靠性区间进行预测研究.仿真实验结果表明,设计尺寸与磨耗到限对应的上述四种工况锁铁垂向上升位移均未达到开锁位,17型车钩防跳性能可靠,该研究方法为车钩的设计与改进提供了技术参考.

17型车钩防跳插销的改进

分析了原17型车钩防跳插销的失效原因,介绍了该防跳插销的改进情况,并对改进效果进行了验证。

17型车钩防跳性能不良的调研分析

针对货车检修过程中17型车钩组装作业时部分车钩防跳性能不良的问题,通过现场调研、原理分析和试验验证,提出了加强17型车钩源头制造质量控制,增加钩体下锁腔的锁铁导向台宽度,提高导向台焊修质量,增加下锁销长度检修标准的解决方案。

17型车钩车钩高度与车体及转向架的关系研究

分析了17型车钩车钩高度与车体和转向架的关系,提出了控制车钩高度的方案,并进行了验证。

Effect of Sm-rich liquid phase on magnetic properties and microstructures of sintered 2:17-type Sm-Co magnet

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.

Twinning,phase boundary structure and development of high coercivity in Fe-rich Sm_(2)Co_(17)-type magnets

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.

Identification of optimal solid solution temperature for Sm_(2)Co_(17)-type permanent magnets with different Fe contents

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).

Correlation of mechanical anisotropy with fine grain strengthening for Sm_(2)Co_(17)-type sintered permanent magnets

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.

新造铁路货车车钩高度控制原因分析及改进措施

分析了新造货车车钩高度不稳定并且调整困难的原因,并提出了控制车钩高度的工艺措施及改进建议。

一种70 T钩尾销挡板焊接定位装置的设计

首先对70 T钩尾销挡板焊接作业现状进行调查分析,发现钩尾销挡板焊修作业,需要两名作业人员来共同完成,由一人托举挡板,另一人进行焊修,存在不安全、定位不准、工作效率低等问题。针对问题,设计出通过压缩风缸支撑的移动式焊接定位装置,主要由定位装置、升降装置、控制装置和走形装置组成。然后对方案进行实施,投入现场使用,最后对工装的效益及推广效果进行了阐述。对具有相同70 T钩尾销焊修作业难题处理提供了思路,可推广应用到全国货车车辆段使用。

Microstructures and coercivity mechanism of 2:17-type Sm-Co magnets with high remanence

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).

Micron-scale 1:5H-based precipitated phase with the lamellar structure of sintered Sm_(2)Co_(17)-based magnets and its potential application

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.

Cellular microstructure modification and high temperature performance enhancement for Sm2Co17-based magnets with different Zr contents

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.

Electrochemical performance of La_(2–x)Sm_xMg_(16)Ni+200 wt.% Ni(x=0, 0.1, 0.2, 0.3, 0.4) alloys

Nanocrystalline and amorphous La_（2–x）Sm_xMg_（16）Ni＋200wt.% Ni（x=0, 0.1, 0.2, 0.3, 0.4） alloys were prepared by mechanical milling technology. The structures of as-cast and milled alloys were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and transmission electron microscopy（TEM）. Electrochemical performance of the alloy was studied by using an automatic galvanostatic system. The electrochemical impedance spectra（EIS） and Tafel polarization curves were measured by electrochemical workstation. The results indicated that the structures of the as-cast and milled alloys presented a multiphase structure with nanocrystalline and amorphous phase, moreover, transforming from nanocrystalline to amorphous phase with Sm doping. With the increase of Sm content, the maximum discharge capacity of the alloy was decreased from 922.6 to 649.1 m Ah/g, the high-rate discharge ability（HRD） was decreased, the cycle stability was strengthened, and the alloy exhibited excellent electrochemical kinetics. In addition, the charge-transfer resistance（R_（ct）） of alloy was lessened from 0.05874 to 0.02953 ？ and the limiting current density（I_L） was descended from 2.08366 to 1.04592 A/g with increasing Sm content.