Magnetization Processes in Ribbons of Soft Magnetic Amorphous Alloys

Using iron-based (Fe–B–Si–C; Fe–Ni–Si–B) and cobalt-based (Co–Fe–Ni–Cr–Mn–Si–B) soft magnetic alloys as examples, we have studied the dependences of the remanence measured using minor hysteresis loops on the maximum induction. The different degrees of stabilization of the 180° and 90° domain walls allows these dependences to be used to analyze the magnetization processes that occur in the rapidly quenched soft magnetic alloys. It has been established from the B_r(B_m) dependences that, in the ribbons of soft magnetic amorphous alloys, the processes of the rotation of the magnetization oriented perpendicular to the ribbon plane start before the end of the processes of the displacement of the walls of domains with planar magnetization. After the end of the magnetization rotation processes, the magnetization processes can be interpreted as the displacement of the domain walls with a planar magnetization accompanied by a decrease in their number and a transition to a bistable state.     

铁和铁合金的塑性变形与磁化

结晶材料通过塑性变形会发生磁物理量的变化,位错周围的磁矩变化会影响到塑性变形磁性体的磁化过程。研究了矫顽力、渐近饱和区域的磁化率与位错组织的相关关系。纯铁和Ａ533Ｂ钢的变形应力与矫顽力有着一定的相关性,矫顽力随着变形量的增加而增大形成一条曲线。Ａ533Ｂ钢...     

Temperature Dependence of Surface Tension of Sn-Ag Alloys

The surface tension of molten Sn-Ag alloys was measured using a specially developed high-accuracy sessile drop apparatus. In this apparatus, a molten sample is dropped onto a R-Al₂O₃ substrate in order to prevent any reaction between the sample and substrate during the heating process. The droplet shape was recorded from two perpendicular directions to confirm its symmetry. The oxygen partial pressure ( $ {P_{{{\text{O}}_2}}} $ ) was controlled by a Mg furnace to a value of about 10^?16 to 10^?15 Pa. The sample compositions used were Sn-20Ag, Sn-50Ag, and Sn-80Ag (at.%) and were alloyed from pure Sn (99.999%) and Ag (99.99%) in the dropping tube. The accuracy of the experimental results was confirmed by an extremely small scatter. The measured temperature dependence of the surface tension of the molten Sn-50Ag (at.%) alloy indicated a characteristic curve that changed from positive to negative with increasing temperature. Furthermore, the surface tension of the molten Sn-20Ag (at.%) alloy has a temperature dependence that changes from flat to negative, while the Sn-80Ag (at.%) alloy has a negative temperature dependence across the whole temperature range. Based on a theoretical discussion using Butler’s equation, these temperature dependencies can be determined by negative straight lines when assuming the surface composition.     

Influence of Deposition Current Density on the Magnetization Behaviour in Electrodeposited Ni-Mn Alloys

Ni-Mn alloys were electrodeposited at different current densities from sulphate baths and their magnetization behaviours at different fields were studied. The magnetization decreases with increase in deposition CD in the absence of additives. The magnetization behaviour of Ni-Mn is different from that of its counterpart i.e. the electrodeposited Fe-Mn system. The system is free from pronounced ferromagnetic coupling between Mn spins. The magnetic moments in high field regions are heavily influenced by the presence of Mn spins.     

In-plane Uniaxial Anisotropy and Magnetization Reversal Mechanism of FeCo Films by Strip Pattern

Strip-like Fe Co films were patterned by a traditional lithograph process from intrinsically isotropic continuous Fe Co films. The strip-patterned Fe Co film shows a strong in-plane uniaxial magnetic anisotropy with easy axis along the length direction of the strip. The angular dependences of remanence ratio, switching field, and coercivity indicate that the magnetization reversal mechanism of the strip-patterned Fe Co film is coherent rotation and domain wall depinning when the applied field is near the hard axis and easy axis, respectively. The consistency of the experimental hysteresis loops of the strip-patterned Fe Co film and calculated hysteresis loops with a simple in-plane uniaxial anisotropy model indicates that the strip-patterned Fe Co film behaves as a single domain. The absence of the domain wall and the strong in-plane anisotropy field make the strip-patterned Fe Co films have much potential for high-frequency application.     

High Entropy Alloys,Miscibility Gaps and the Rose Geometry

Recent review articles on high entropy alloys (HEAs) provide little information about miscibility gaps in multicomponent systems, especially about how to respond with alloying should they be found. Also, there is a lack of information about how miscibility gaps might appear on calculated or measured multicomponent phase diagrams. In this work concepts concerning miscibility gaps that form in binary and ternary systems are reviewed. Then the work is extended to alloys with more components including HEAs. The previous work predicts that there are significant differences between binary systems and those with three or more components. For example, miscibility gaps do not form in binary systems that have a negative heat of mixing, but they do form in ternary systems. Also, ternary systems with a positive heat of mixing can have their stability temperature lowered by adding ternary components that add positive heats of mixing. The morphology and topology of multicomponent/multiphase miscibility gaps differ from typical phase diagrams, as well. For example, one type of miscibility gap is said to have the rose geometry, because of its floral design. Normally only 2-phase miscibility gaps can form in binary and ternary systems. However using the Graph Method it is suggested that 3-phase miscibility gaps might form in HEA systems, even while trying to avoid them. A conclusion of this investigation is that with additional computational and experimental work it may be possible to expand the boundaries of where HEAs can be found.     

纳米掺杂Ag（SnFe）O2电接触合金的研究

利用化学共沉淀、高能球磨技术及热压烧结等方法制备出纳米掺杂Ag（SnFe）O2触头合金，通过X射线衍射（XRD）、透射电镜（TEM）和冷场发射扫描电镜（FESEM）等对合金触头及其燃弧性能进行了分析。结果发现：Fe元素的加入，使Sn02纳米颗粒在550℃以下焙烧制粉和750℃以下块体烧结成型时都未明显长大，保持在20nm左右，制备的触头合金呈现纳米第二相弥散均匀分布在Ag基体中。在模拟电弧侵蚀试验中，该合金电弧阴极斑点铺展在较大区域，形成多点燃弧形貌，有效降低燃弧时间和电弧电流，分散电弧能量，使阴极斑点没有明显的液体喷溅、Ag的蒸发和第二相的分解，同时非晶的纳米第二相与Ag的润湿性更好，可进一步增加熔体粘度，提高耐电弧侵蚀性能。     

铝锂合金晶间腐蚀敏感性与时效阶段的相关性

研究了不含Zn及0.72%Zn微合金化的Al-3.7Cu-1.15Li-0.5Mg合金T6态时效(150及175℃)不同时间后的晶间腐蚀行为,建立了其腐蚀-时效进程状态图。结果表明,Zn微合金化铝锂合金晶间腐蚀敏感性略低于不含Zn微合金化的铝锂合金。随时效进程的发展,铝锂合金腐蚀类型变化规律为:孔蚀或局部晶间腐蚀(时效早期),全面晶间腐蚀(欠时效阶段),局部晶间腐蚀(近峰时效阶段),孔蚀(过时效阶段)。晶间腐蚀深度随时效时间延长呈先增加而后降低的规律。时效时间延长,一方面晶界析出相逐渐粗化并且呈不连续分布,另一方面晶内T1相及θ相析出,晶内电位降低,晶界及晶内电位差减小,从而导致上述腐蚀类型的变化。     

Isotropic Alloys of the Sm – Co System for Ring Magnets with Radial Magnetization

Metal Science and Heat Treatment - Methodology of creation of ring permanent magnets with radial magnetization from an isotropic alloy of the Sm – Co system with induction coercivity no lower...     

Zr-Sn-Nb-Fe合金中铌的存在方式及其与热处理的关系

用 SEM 的波谱(WD)分析手段,定性研究了合金元素铌在 Zr-Sn-Nb-Fe 合金中的存在方式及其与中间退火工艺的关系。研究结果表明添加的合金元素铌主要存在于 Laves 相中,并且随中间退火温度升高,第二相中铌含量增加。铌在 α-Zr 中的含量随退火温度升高而降低,可降低至小于 1×10-4,这与二元 Zr-Nb 合金中合金元素铌的固溶度随温度升高而增加明显不同。铌和铁、铬共存于锆合金中时,将与铁、铬一起优先形成沉淀相,导致合金元素主要存在于第二相中,并出现其在 α-Zr 中固溶量随退火温度升高而降低的现象;其原因可归结为随退火温度升高铌扩散能力增加,从而导致在第二相中含量增加。     

极端晶化条件下纳米双相永磁合金快淬薄带的晶化研究

在常规晶化退火工艺条件下纳米双相永磁合金快淬非晶薄带的晶化过程中,α-Fe相通常在低温优先析出,这导致了α-Fe晶粒过于粗大并严重损害了材料磁性能。针对这一问题,近期有一些学者对极端晶化条件下非晶快淬薄带的晶化行为和机制进行了仔细的研究。本文对这些研究进行了综述和分析。     

Co和Zr元素对纳米晶复合NdFeB永磁合金晶化行为和磁性能的影响

利用熔体快淬法和晶化退火处理工艺制备纳米晶复合NdFeB永磁合金,研究添加Co和Zr元素对合金晶化行为、微结构和磁性能的影响.结果表明,添加Co元素降低了晶化相的析出温度,提高了合金的剩磁;进一步增加Zr元素后,合金的晶化行为由两步晶化变为软硬磁相同步析出,合金的矫顽力明显提高,晶粒得到细化,软、硬磁相之间的交换耦合作用显著增强,从而使合金Nd9.5Fe76Co5Zr3B6.5表现出优异的综合磁性能,即Jr=0.93 T,iHc=687 kA/m,(BH)max=129 kJ/m3.     

Fe掺杂对纳米复合Ag-SnO2电接触合金电弧演化行为的影响

应用高速数字摄像机和扫描电镜对纳米复合Ag-SnO2，Fe掺杂的纳米复合Ag-SnO2及商用Ag—SnO2-In2O3电接触合金的电弧演化过程和阴极斑点进行了比较研究。结果显示：空气中电弧的演化过程可以分为起弧、稳定燃烧和衰减3个阶段。Fe掺杂后，纳米复合电接触合金电弧演化过程的形弧时间是商用合金的2倍；对触点表面烧蚀起主要作用的稳定燃烧时间短；电弧弧根对应的阴极斑点数量多、跳动迅速、运动区域大；电弧弧根在阴极表面停留的时间短，热流输入少，使其燃弧后阴极斑点分散，烧蚀轻微，具有较好的耐电弧侵蚀性能。     

Composition Dependence of the Kinetics and Mechanisms of Thermal Oxidation of Titanium-Tantalum Alloys

The oxidation behavior of titanium-tantalumalloys was investigated with respective concentrationsof each element ranging from 0 to 100 wt.%. Alloys wereexposed to argon-20% oxygen at 800 to 1400°C. Theslowest oxidation rates were observed in alloys with5-20% Ta. The oxidation kinetics of alloys containingless than approximately 40% Ta were approximatelyparabolic. Pure Ta exhibited nearly linear kinetics. Alloys containing 50% or more Taexhibited paralinear kinetics. The activation energiesfor oxidation ranged between 232 kJ/mole for pure Ti and119 kJ/mole for pure Ta, with the activation energies of the alloys falling between these values andgenerally decreasing with increasing Ta content. Theactivation energies for oxidation of the end members, Tiand Ta, agree well with published values for the activation energies for diffusion of oxygenin -Ti and Ta. Scale formation in the alloys wasfound to be complex exhibiting various layers of Ti-,Ta-, and TiTa-oxides. The outermost layer of the oxidized alloys was predominately rutile(TiO₂). Beneath the TiO₂ grew avariety of other oxides with the Ta content generallyincreasing with proximity to the metal-oxide interface.It was found that the most oxidation-resistant alloys hadcompositions falling between Ti₅Ta andTi-15Ta. Although Ta stabilizes the -phase of Ti,the kinetics of oxidation appeared to be rate limited byoxygen transport through the oxygen-stabilized -phase.However, the kinetics are complicated by the formationof a complex oxide, which cracks periodically. Tantalumappears to increase the compositional range ofoxygen-stabilized -phase and reduces both the solubilityof oxygen and diffusivity of Ti in the - and-phases.     

纳米晶双相Nd10．5Fe78-xCo5ZrxB6．5合金磁性能与结构的研究

用熔体快淬法和晶化热处理工艺制备Nd10．5Fe78-xCo5ZrxB6．5（x=0，2，3，4，5）纳米晶双相永磁材料，研究了其磁性能与结构的变化。结果表明：适量地添加（2at％）Zr能显著提高合金的内禀矫顽力，并且可以有效抑制合金中的软、硬磁相的晶粒长大，获得晶粒尺寸为20nm的微观结构，使得合金中的软磁相和硬磁相发生比较充分的交换耦合作用，从而有效地提高合金的磁性能。     

环境因素对铝合金大气腐蚀的影响及其动态变化规律研究

采用灰关联分析法分别计算了环境因素与三种铝及铝合金在1、3、6、10年大气暴露后平均腐蚀速率的关联度,并进行了排序.对LY12cz、LY12、L6M材料在不同暴露时间的主要环境影响因素及其动态变化规律进行了分析.结果表明,SO2、Cl-、T、RH>80%等环境因素对铝及铝合金腐蚀作用显著;尤其是SO2,而NH3和非水溶性降尘(D)的影响基本可忽略.RH>80%影响的加强可促进Cl-对铝合金腐蚀的影响,且T影响强时,Cl-和SO2有协同作用.灰关联度计算结果与各试验站实际的大气腐蚀结果相一致.     

Dependence on the Chromium Content of the High-Temperature Oxidation Behavior of Ta-Rich Nickel-Based Cast Alloys

The high-temperature stability of primary tantalum carbides is a problem of importance for chromium-rich cast alloys, based on cobalt or nickel. The focus of this study was nickel-based alloys, as these alloys are particularly sensitive to a lack of TaC in the as-cast state and by dissolution due to high-temperature exposure. In this work, a possible way for promoting the formation of many TaC precipitates by changing from the usual 30 wt% chromium content was investigated. Five alloys with Cr content varying from 10 to 50 wt% were prepared and then subjected to microstructure characterization and to oxidation tests. In contrast with what was expected, decreasing the Cr content in comparison with the Ni–30Cr–0.4C–6Ta reference alloy did not succeed in obtaining more TaC precipitates, but instead had the opposite effect. Concerning the high-temperature oxidation behavior at 1127 and 1237 °C, loss of resistance was observed only for a Cr content at the lower level of 10 wt%. It was noticed that a subscale CrTaO₄ developed during oxidation and seemed to promote oxide spallation during cooling.     

Dependence of Microstructure, Texture and Tensile Properties on Working Conditions in Indirect-Extruded Mg-6Sn Alloys

通过光学显微镜（OM）、扫描电子显微镜（SEM）、X射线衍射仪（XRD）和电子材料试验机研究了反向挤压Mg-6Sn合金的组织、织构和拉伸性能与挤压条件（挤压速度和初始坯料温度）间的依赖关系。研究结果表明：反向挤压 Mg-6Sn 合金的晶粒尺寸、再结晶体积分数和动态析出第二相体积分数在很大程度上取决于反向挤压参数,随着挤压速度和初始坯料温度的升高,合金的织构强度减弱。通过控制挤压速度和初始坯料温度,经高温挤压后的合金表现出最高的抗拉强度。对于商业 AZ31 镁合金而言,合金的强度随着挤压温度的升高而降低。本研究的 Mg-6Sn 合金经高温挤压后的抗拉强度和经低温挤压后的 AZ31 合金相当。上述研究结果表明 Mg-6Sn 合金是一种适合于高速度挤压的新型合金系。