Aging effects in the nonequilibrium quantum spin glass in weak magnetic fields

This work is devoted to a theoretical study of effects of aging in a disordered quantum system being in contact with an interior surroundings and subject to the influence of external alternating fields. The dissipation is realized via coupling with a set of independent harmonic oscillators, which imitate a quantum thermostat (bath), and with an external field. Using the formalism of closed-path integrals, dynamic equations are derived for the autocorrelation and linear-response functions. The dependences of correlation, response, and integrated-response functions on temperature, waiting time, and quantum parameter are studied. The effect of external fields on the behavior of these functions is analyzed. A qualitative agreement with experimental data have been found.     

Analysis on three-sublattice model of magnetic properties in rare-earth iron garnets under high magnetic fields

In this paper, based on the molecular field theory, a new and improved three-sublattice model on studying the magnetic properties of ferrimagnetic rare-earth iron garnet in high magnetic fields is introduced. Here, the effective exchange field is described as H_i = λM = λχH_e, where λ is the coefficient associated with the molecular field, χ is the effective magnetic susceptibility, and H_e is external magnetic fields. As is known, the magnetic sublattices in rare-earth iron garnets can be classified three kinds labeled as a, c and d, in our calculations, whose magnetizations are defined as M_a, M_c and M_d, respectively. Then, using this model, the temperature and field dependences of the total magnetization in Dy₃Fe₅O₁₂ (DyIG) are discussed. Meanwhile, the magnetizations of the three kinds of magnetic sublattices are analyzed. Furthermore, our theory suggests that the coefficients α_i associated with λ and χ in DyIG show obvious anisotropic, temperature-dependence and field-dependence characteristics. And, the theoretical calculations exactly fit the experimental data.     

横纵磁场下铁基合金堆焊层组织性能的对比分析

将Fe5自熔合金采用等离子弧堆焊设备堆焊到低碳钢表面,在堆焊的过程中施加直流横向和直流纵向磁场,并调节磁场参数和堆焊工艺参数,对不同参数下堆焊试样进行硬度和磨损试验,采用显微电镜和扫描电镜对堆焊层显微组织进行分析,研究两种磁场状态下堆焊层组织、性能的差异性,并对其中的机理进行探究.结果表明,直流横向磁场和直流纵向磁场均可提高硬质相的形核率,改善堆焊层的组织性能;横向磁场作用下堆焊层中硬质相杂乱分析,而纵向磁场使堆焊层中的硬质相以规则的"六边形"出现,这使得横向磁场对提高堆焊层的硬度较明显,纵向磁场对提高堆焊层耐磨性效果明显.     

Effect of high magnetic fields on the solidification microstructure of an Al-Mn alloy

The effect of high magnetic fields on the morphology of Al-Mn phases was investigated. It is found that the tropism and the alignment of Al₆Mn precipitated phases become regular under high magnetic fields. The stronger the high magnetic fields, the more regular the alignment of Al₆Mn precipitated phases. Al₆Mn precipitated phases can generate oriented alignment and aggregation under high magnetic fields through the observation of the quenched microstructure of the Al-Mn alloy at different temperatures. Meanwhile, the number of Al₆Mn phases increases continuously along with the increasing function time of high magnetic fields. X-ray diffraction also indicates that Al₆Mn phases generate obvious tropism under high magnetic fields. The process of aggregation and growth of Al₆Mn precipitated phases under the function of high magnetic fields after orientation were analyzed and discussed.     

外加纵向磁场对堆焊层金属性能的影响

对低碳钢表面进行等离子弧堆焊时外加纵向磁场,得出了磁场强度对堆焊层金属的硬度和耐磨性的影响规律;电磁搅拌能够细化堆焊层金属的组织,控制硬质相的形态及分布,从而可提高堆焊层金属的综合力学性能.     

Effect of high magnetic fields on the solidification microstructure of an AI-Mn alloy

The effect of high magnetic fields on the morphology of Al-Mn phases was investigated. It is found that the tropism and the alignment of Al6Mn precipitated phases become regular under high magnetic fields. The stronger the high magnetic fields, the more regular the alignment of AI6Mn precipitated phases. Al6Mn precipitated phases can generate oriented alignment and aggregation under high magnetic fields through the observation of the quenched microstructure of the Al-Mn alloy at different temperatures. Meanwhile, the number of Al6Mn phases increases continuously along with the increasing function time of high magnetic fields. X-ray diffraction also indicates that Al6Mnphases generate obvious tropism under high magnetic fields. The process of aggregation and growth of Al6Mn precipitated phases under the function of high magnetic fields after orientation were analyzed and discussed.     

高频交变磁场对大电流GMAW熔滴过渡和飞溅率的影响

在熔化极气体保护焊过程中,采用大送丝速度,增大焊接电流和焊丝伸出长度是提高焊接熔敷率的直接途径.但当熔滴过渡转变为旋转射流过渡时,电弧不稳,飞溅增大,焊缝成形变差.施加不同频率的纵向交变磁场,对焊缝成形进行控制.采用高速摄像技术,拍摄焊接过程中的电弧形态和熔滴过渡,研究不同频率的磁场对熔滴过渡和焊接飞溅率的影响规律.结果表明,熔滴过渡形式不同,产生飞溅的机理不同;外加频率为1 000 Hz纵向交变磁场时,电弧的旋转半径减小,电弧的挺度增大,旋转射流过渡时电弧更稳定,焊接飞溅率降低,焊缝成形改善.     

Magnetoelastic effect in plastically deformed ferromagnetic steels in weak magnetic fields

A sharp decrease in the magnitude of magnetoelastic effect M _σ as a result of unloading after preliminary plastic extension has been revealed in ferromagnetic steels in weak magnetic fields. The physical origin of this effect and the dependence of M _σ on σ (in the elastic region) and on deformations ɛ (in the plastic region) are considered.     

Effect of roller die drawing on structure, texture and other properties of high carbon steel wires

In the work the effect of application of roller dies in process of drawing of high carbon steel wires for their structure, texture, residual stresses, surface roughness and mechanical properties has been investigated. Among structural features alignment of cementite lamellae to the wire axis by means of SEM and Pericolor 1500 has been quantitatively determined. Degree of cementite lamellae fracture in colonies parallel to wire axis has been estimated by Langford method. Obtained results were compared with those structural features for conventionally and hydrodynamically drawn wires. It has been found that degree of alignment of cementite lamellae in wires drawn in roller dies was smaller than in wires drawn conventionally and hydrodynamically but in the case of fracture degree the opposite result was noticed. Residual stresses were determined by electrochemical reversal pickling in water solution of sulphuric acid. A significant drop of longitudinal residual stresses in surface layer of wires drawn in roller die has been observed as compared to those stresses for conventionally and hydrodynamically drawn wires. Surface roughness of wires was measured with FORM TALYSURF profilographometer. It has been proved thad roller die drawing has formed very smooth surface with much smaller longitudinal and circumferential roghness parameters that for surface of wires drawn conventionally and hydrodynamically. In the work the tensile, yield and fatigue strength of tested wires were determined. It has been concluded that roller die drawing has many advantages as compared to conventional process and should be implemented in wire industry for larger scale.     

外加横向磁场对高速GMAW焊缝成形的影响

对于高速熔化极气体保护焊接（GMAW）过程,当焊接速度超过临界值后,会出现驼峰焊道,焊缝成形变差.研究证明,熔池中动量很大的后向液体流是产生驼峰焊道的主要原因.研发了外加横向磁场发生装置,通过产生的电磁力来抑制后向液体流的动量,从而抑制驼峰焊道的形成.应用特斯拉计测试和考察了工件上磁感应强度大小及分布的影响因素.通过开展焊接工艺试验分析了不同强度的外加磁场作用下的焊缝成形规律.结果表明,外加横向磁场能明显调控熔池流态,有效抑制驼峰焊道和咬边等缺陷,显著改善焊缝成形,提高临界焊接速度.     

纵向直流磁场对铝铜熔钎焊接头组织和性能的影响

采用TIG焊进行铝铜异种材料熔钎焊对接试验,通过添加Zn-2%Al药芯焊丝调控焊缝成分,并施加纵向直流磁场调控界面组织,接头力学性能显著提高. 结果表明,相比于无磁场,在纵向直流磁场的作用下,Cu侧IMC层的形状、厚度和化合物种类均发生变化:平均厚度明显变薄,由32.8 μm降至14.6 μm;形状由平直变为弯曲,起到“机械咬合”作用;Cu侧IMC层Al_4.2Cu_3.2Zn_0.7三元化合物的出现抑制了硬脆的AlCu与Al₂Cu化合物的生长,接头性能升高. 添加直流磁场后,接头抗拉强度均比无磁场时高,且接头抗拉强度随着磁场强度的增加呈现先增大后减小的趋势. 当焊接电流I = 95 A,焊接电压U = 16 V,焊接速度v = 140 mm/min,磁场强度B = 10 mT时,接头抗拉强度最高,达到110.8 MPa,比无磁场升高了约24%.     

Effect of sintering process on microstructure and magnetic properties of high frequency power ferrite

An oxide ceramic process was adopted to prepare high frequency manganese-zinc (MnZn) power ferrite. In combination with the microstructure analysis of material, the influences of sintering process on initial permeability (μi) and high frequency loss in unit volume (Pcv) of MnZn power ferrite were investigated. The results show that in order to obtain fine microstructure and high frequency properties, the preferable sintering temperature and atmosphere are 1230 ℃ and oxygen partial pressure ( PO2) of 4%, respectively.     

Effect of high gradient magnetic fields on the anodic behaviour and localized corrosion of iron in sulphuric acid solutions

The influence of high gradient magnetic fields on the anodic dissolution of iron in sulphuric acid solutions and the localization of the corrosion attack is investigated by means of potentiodynamic and potentiostatic polarization experiments and subsequent surface profile analysis. A localization of the material loss is observed in every potential region of the anodic Fe dissolution except from the passive region. The impact of the magnetic field on the anodic current density and the localization of the corrosion attack are explained by the action of the Lorentz force and the magnetic field gradient force.     

横向稳恒磁场对M2高速钢定向凝固过程V元素含量分布的影响

通过数值模拟探讨了M2高速钢定向凝固过程中无外加磁场以及外加0.5T横向稳恒磁场对V含量分布的影响,并建立数值模型,将模拟结果与试验结果进行对比,两者结果相符。数值模拟分析结果显示:当不加磁场时,坩埚中对流由自然对流占主导,并不会发生溶质的单向传输;当外加0.5T横向磁场时,坩埚中对流由单向的热电磁流主导,单向运输的溶质会富集于试样一侧。     

热处理工艺对钢丝的组织及力学性能的影响

对直径ф3.2 mm的半成品钢丝采用重新奥氏体化后研究在不同风冷条件下力学性能的变化,探索了奥氏体化温度及风冷速度对70钢丝性能的影响关系.结果表明,随着保温温度增加钢丝的伸长率和断面收缩率随之下降;在相同奥氏体化温度下随冷却速度的加快,钢丝抗拉强度呈上升趋势,伸长率和断面收缩率没明显变化.钢丝在790℃奥氏体化,风冷时风机频率控制在50 Hz时可获得接近铅浴处理的力学性能.     

横向交流脉冲磁场对堆焊金属组织及性能的影响

通过在低碳钢表面进行等离子弧堆焊时外加交流脉冲横向磁场,研究了交流脉冲磁场对镍基自熔合金组织及性能的影响,并利用光学金相、X射线衍射、显微硬度和湿砂橡胶轮磨损试验等方法,系统分析了不同脉冲磁场电流、占空比作用下的堆焊试样的硬度、耐磨性及组织.结果表明,外加横向交流脉冲磁场可以有效改善堆焊层金属的结晶形态,细化晶粒,在适当的脉冲磁场电流、占空比作用下,可以获得最佳的电磁搅拌效果,增加堆焊层金属中硬质相的数量,控制硬质相的生长方向,提高等离子弧堆焊层的硬度和耐磨性.     

Effect of magnetic fields on pulse plating of cobalt films

Magnetic fields parallel to the electrodes were introduced during a pulse plating process to obtain cobalt thin films from alkaline baths. Ef-fects of different magnetic intensities on the composition, microstructure, and magnetic properties of cobalt thin films were investigated. It was found that the deposition speed increased gradually with the increase of magnetic intensity. Almost all of the deposited films were crys-talline and showed Co(002), Co(100) peaks. With the rise on the magnetic intensity, the intensity of Co (002) peak raised gradually. Mag-netic fields would induce cobalt growing along (002) orientation. The films were densely covered with typical nodular structure. Films of smaller grain size and smooth surface could be formed under high magnetic intensity (1 T) as a result of magnetic force and MHD effects. Moreover, higher magnetic intensity induced larger saturation magnetization and lower coercivity. With the rise on magnetic intensity, cobalt contents in the films increased gradually, which led to the rise of saturation magnetization.     

Effect of Zr and Sc on mechanical properties and electrical conductivities of Al wires

In order to obtain the Al wires with good mechanical properties and high electrical conductivities, conductive wires of Al–0.16Zr, Al–0.16Sc, Al–0.12Sc–0.04Zr (mass fraction, %) and pure Al (99.996%) were produced with the diameter of 9.5 mm by continuous rheo-extrusion technology, and the extruded materials were heat treated and analyzed. The results show that the separate additions of 0.16% Sc and 0.16% Zr to pure Al improve the ultimate tensile strength but reduce the electrical conductivity, and the similar trend is found in the Al–0.12Sc–0.04Zr alloy. After the subsequent heat treatment, the wire with the optimum comprehensive properties is Al–0.12Sc–0.04Zr alloy, of which the ultimate tensile strength and electrical conductivity reach 160 MPa and 64.03% (IACS), respectively.     

Pr对Sn58Bi钎料微观组织和性能的影响

通过在Sn58Bi合金钎料中添加Pr制备了新型无铅钎料,用该钎料进行焊接后,测定了Pr添加量对焊后钎料的晶格变化、润湿性和钎焊接头抗拉强度的影响。XRD衍射结果表明,Pr的添加能够导致钎料晶格畸变。SEM结果表明,微量Pr的添加可以抑制Bi相长大粗化,细化钎料晶粒。润湿性能研究表明,随着Pr量的增加,Sn58Bi 钎料的润湿性有所改善,当添加质量分数为1.5% 的Pr时,钎料的铺展率由81.97%扩大到88.41%,增加了7.86%;钎料力学性能显示,未添加Pr时钎焊接头抗拉强度为7.631 8 MPa,而随着Pr的加入,其抗拉强度增加,当添加质量分数为1.5%的Pr,钎焊接头抗拉强度最大为11.126 3 MPa,提高了45.79%。综合表明,适量Pr的添加可以有效改善Sn58Bi钎料的组织结构、润湿性和抗拉强度。创新点： (1)添加微量稀土元素制备Sn58BiPr无铅焊料。(2)Pr的掺入可使焊料晶格畸变、细化焊料晶粒。(3)添加Pr能有效改善焊料的润湿性和抗拉强度。