The oxidation behaviour of amorphous and crystalline Fe78Si9B13

A combination of thermogravimetry, scanning and transmission electron microscopy, electron probe microanalysis and differential scanning calorimetry has been used to investigate the oxidation kinetics, and oxide morphology, structure and composition in amorphous and crystalline Fe₇₈Si₉B₁₃ alloys. Kinetic data indicate that the oxidation reactions of both amorphous and crystalline Fe₇₈Si₉B₁₃ obey a parabolic rate law over the temperature range 300 to 450°C with activation energies of 120 and 86 kJ/mol respectively, indicating that grain boundary diffusion is probably the rate controlling process. The parabolic rate constant for oxidation of crystalline Fe₇₈Si₉B₁₃ is consistently higher than for amorphous Fe₇₈Si₉B₁₃ over the temperature range 300–450°C, so that the amorphous alloy always shows a better oxidation resistance. Electron microscopy and electron probe microanalysis show that the oxide scales formed on both amorphous and crystalline Fe₇₈Si₉B₁₃ consist of SiO₂, Fe₃O₄ and Fe₂O₃, but the detailed microstructure and compositions are different. The oxide scale formed on amorphous Fe₇₈Si₉B₁₃ contains more SiO₂ and has a small particle size, while the oxide scale formed on crystalline Fe₇₈Si₉B₁₃ contains more Fe₃O₄ and consists of larger particles. The difference in oxide growth between amorphous and crystalline Fe₇₈Si₉B₁₃ is caused by the difference in alloy microstructure.     

Mechanical behaviour of both sides of an amorphous Fe78B14Si8 alloy ribbon as determined from miniaturized disk-bend tests

A miniaturized disk-bend test was used to examine the mechanical properties of the “air” and “wheel” sides of melt-spun ribbons, 30 μm thick, of an amorphous Fe₇₈B₁₄Si₈ alloy. The specimens were 3 mm in diameter and were tested clamped at their perimeters. Deformation was non-linear, with the load rising to a maximum value signifying the onset of fracture. Crack propagation was accompanied by substantial elongations at lower loads. The displacement of the center of the specimen at peak load was used a measure of its ductility. The wheel side is consistently harder, stronger and more ductile than the air side. We propose that this is due to the numerous regions of low free volume at the wheel side, produced when air is entrapped between the melt and the wheel, combined with local enrichement of boron and/or silicon in these same regions. These strong regions are interspersed with those that solidified at the most rapid rate and which have the largest free volume, highest ductility, but lowest hardness and strength. The heterogeneous distribution of free volume at the wheel side invests it with its high strength and ductility; the air side has properties between these two extremes. The role of ribbon surface topography in the initiation of fracture is also discussed.     

Effect of high pressure on microstructure of crystallizing amorphous Nd9Fe85B6 alloy

The effect of high pressure on the microstructure of annealed amorphous Nd9Fe85B6 alloy was studied. It was found that application of high pressure made the microstructure of the crystallized alloy much more homogeneous. The average grain size of the Nd2Fe14B phase decreased with the increase of pressure, whereas, the size of the α-Fe first increased when a pressure of 1 GPa was applied and then decreased with further increase of pressure. Pressure-induced （410） texture of the Nd2Fe14B phase was also observed. The present study suggested an effective route for controlling the microstructure in a nanoscale solid.     

电流退火对铁基非晶合金Fe78Si9B13薄带巨应力阻抗效应的影响

研究了电流退火工艺对非晶Fe78Si9B13薄带巨应力阻抗效应的影响.实验结果表明,在外加应力下对非晶合金进行电流退火,巨应力阻抗效应显著提高,并且ΔZ/Z最大值随退火电流密度的增加先增加然后减小.Fe78Si9B13合金在40 MPa预应力下,经34 A/mm2电流退火后,阻抗的最大相对变化率达到180 %.认为上述阻抗变化与电流退火过程中应力感生各向异性有关.     

磁场退火对Fe80Si9B11非晶合金的磁致伸缩特性影响

摘要：利用激光多普勒法测量50Hz下非晶合金带材的磁致伸缩曲线,研究了磁场退火对Fe80Si9B11非晶合金带材的磁致伸缩特性的影响。结果显示,在相同的磁场强度下非晶带材经横磁退火后磁致伸缩最大,无磁场退火次之,纵磁退火时最小。然后,采用Kerr方法观察了非晶合金带材的磁畴形貌,从微观结构上解释了经不同磁场退火后磁致伸缩大小不同的机理。最后,对无磁场退火、横磁退火和纵磁退火后的Fe80Si9B11铁基非晶合金铁芯进行了噪音测试。结果显示,在相同的频率和磁通密度下,非晶合金铁芯经横磁退火后噪音最大,无磁场退火次之,纵磁退火时噪音最小,与非晶合金带材经不同磁场热处理后磁致伸缩大小的规律一致。为解决非晶合金铁芯在实际应用中的噪音问题提供了参考。     

Fe73.5 Cu1 Nb3 Si13.5 B9非晶合金的激光晶化

用CO2连续激光在不同功率、相同的速度条件下辐照Fe73.5Cu1Nb3Si13.5B9非晶带，然后用穆斯堡尔谱详细研究材料的微观结构。研究发现当扫描速度和散文斑直径一定的情况下，适当选择激光功率，Fe73.5Cu1Nb3Si13.5B9可以实现微量晶化。     

Casting Atmosphere Effects on the Precipitates, Magnetism, and Corrosion Resistance of Fe78Si9B13 Glassy Alloys

The precipitates, magnetism, and corrosion resistance of Fe₇₈Si₉B₁₃ glassy samples fabricated in vacuum and air atmospheres (labeled as VAC and AIR samples, respectively) were studied. The findings show that the fraction of the amorphous phase in VAC samples is lower than that in the AIR counterparts. The Fe phase in VAC samples grows preferentially along the 〈200〉 orientation. The distribution of magnetization M ₄₀₀₀ of VAC samples oriented parallel and orthogonal to the field (H _// and H _⊥) at H = 4000 Oe is more scattered than AIR samples. The corrosion resistance of VAC samples is lower than AIR counterparts, which can be attributed to the minor alloying effect of oxygen and the passive effect of silicon atoms supplied from the amorphous phase.     

Localized vs homogeneous deformation in Fe82B15Si3 amorphous alloy

Amorphous alloys are known to deform plastically either by a localized shear mode or in a homogeneous manner. Conditions that favor homogeneous deformation in an amorphous alloy consisting of 82Fe, 15B and 3Si in at. pct have been established by a free-bend test over a range of temperatures. These results are in turn related to the stress-strain rate-temperature relationship obtained by a load relaxation testing method. The intense, localized shear deformation is shown to occur at relatively high strain rate and low temperature regions where the rate sensitivity of flow stress,m, is small. With increasingm, plastic flow tends to take place homogeneously provided that the mode of deformation remains stable. The strain rate sensitivity of flow stress increases with decreasing strain rate and increasing temperature; the computed diffuse shear transformation zone also changes in the same manner. However, the general trend changes above the glass transition temperature, i.e., the diffuse shear transformation zone decreases and the flow strength increases with increasing temperature.     

CO2激光辐照工艺对非晶Fe73.5Cu1Nb3S13.5B9合金晶化的影响

在较低激光功率(40～170 W)和两种扫描速度(10mm/s,5mm/s)辐照条件下,研究了CO2激光辐照工艺对非晶Fe73.5Cu1Nb3S13.5B9合金晶化行为的影响.用穆斯堡尔谱(MS)技术对原始态和晶化后样品进行了结构分析.研究发现:非晶Fe73.5Cu1Nb3S13.5B9表面产生了少量晶化,晶化相为Fe-Si结构;晶化量在2.1%～3.57%内,随激光功率的增加而增加.当激光功率较低时,低扫描速度对晶化的促进作用大于激光功率的作用;但是,随激光功率增大,速度的影响变弱.表面微观硬度随激光功率的增加而增加.     

Magnetic properties and fine structure of amorphous Fe–Ni–Si–B alloys

The magnetic properties and Mossbauer spectra of amorphous 2NSR alloy samples are investigated after quenching and after tempering for different times at 520°C. After quenching, the alloy is inhomogeneous. Tempering of alloy samples below the crystallization temperature (540°C) raises the Curie temperature and the mean superfine field at the iron nuclei. Tempering leads to complex changes in the saturation magnetization. The changes in magnetic properties are analyzed.     

Thermo-Calc calculations and studies of the heating process of Fe83Si4B13 alloy

The microstructural changes of Fe_(83)Si_4B_(13) amorphous mother alloy during the heating process were investigated by Laser Scanning Confocal Microscopy( LSCM),and the phase transformation was determined by the Thermo-Calc calculations. The differences in the melting points measured by Differential Scanning Calorimetry( DSC)and LSCM,and those obtained by Thermo-Calc calculations were also discussed. It is found that the melting points measured by DSC and LSCM are relatively similar,whereas the onset and end of the melting temperatures calculated by Thermo-Calc software are higher than those measured by DSC and observed by LSCM.     

Fe元素对ZA27合金显微组织和力学性能的影响

在ZA27合金中添加0.5%~2%的Fe元素,利用金相、扫描电镜(SEM)、能谱分析(EDS)、X射线扫描(XRD)、拉伸实验等测试手段,研究Fe含量对ZA27合金显微组织和力学性能的影响。结果表明:不同Fe含量的ZA27合金基体组织均由富铝的α相和富锌的η相组成。Fe元素以FeAl3金属间化合物的形式分布于基体中。随Fe含量增加,FeAl3的含量增多、尺寸增大。FeAl3能阻碍晶界迁移,起到细化枝晶的作用。研究还发现,室温下,随Fe含量增加,ZA27的强度和伸长率均降低;150℃高温下,Fe含量为1.5%左右的ZA27合金抗拉强度达192.75MPa,比未加Fe元素的ZA27合金提高约54.4%,伸长率达15.65%,从而获得兼具高强度和高塑性的高温ZA27合金。     

The microstructure evolution of a Fe73.5Si13.5B9Nb3Cu1 nanocrystalline soft magnetic material

The microstructure evolution in the course of crystallization of a splat-quenched Fe_73,5Si_13.5B₉Nb₃Cu₁ amorphous alloy was investigated by atom probe field ion microscopy (APFIM) and high resolution transmission electron microscopy (HRTEM). All the alloying elements were found to be distributed homogeneously as an amorphous solid solution in the as-quenched state. At an initial stage of annealing, a concentration fluctuation of Cu was found to occur. Cu formed clusters of a few nanometer diameter and their composition was found to be approximately 30 at.% Cu at the beginning. In the later stage, a b.c.c. FeSi solid solution and the B and Nb enriched amorphous phase with the smaller Si content were found to coexist. In addition to these two phases, Cu enriched particles containing approximately 60 at.% Cu were found to be present in the intergranular regions, although we were not successful yet to determine whether this was a crystalline or amorphous phase. Based on these observations, we discuss the crystallization process of this alloy at 550°C which leads to the emergence of excellent soft magnetic properties.     

非晶态Ni-B合金镀层的组织结构和耐蚀性的实验研究

用金相显微镜、电子探针、X射线衍仪和全浸腐蚀实验方法研究化学镀Ni-B合金层的组织结构和耐蚀性,并与晶态Ni-P合金镀层和Q235钢基体进行对比。实验结果表明,非晶态Ni-B合金镀层在硫酸溶液中具有较好的耐蚀性。     

The oxidation behaviour of amorphous alloy Fe40Ni40P14B6

A combination of thermogravimetry, optical microscopy, scanning and transmission electron microscopy, electron probe microanalysis and differential scanning calorimetry has been used to investigate the oxidation behaviour of amorphous Fe₄₀Ni₄₀P₁₄B₆. The oxide layer formed on amorphous Fe₄₀Ni₄₀uB₆ has a whisker-like α-Fe₂O3 structure, which grows very rapidly to build up a thick layer of oxide. Kinetic data indicate that the oxidation of amorphous Fe₄₀Ni₄₀P₁₄B₆ obeys a parabolic rate law as long as the alloy remains amorphous and the rate controlling process is diffusion of iron in the amorphous alloy matrix. However, the oxidation rate drops sharply if crystallization of amorphous Fe₄₀Ni₄₀P₁₄B₆ takes place during oxidation annealing. Crystalline Fe₄₀Ni₄₀P₁₄B₆ also obeys a parabolic rate law but with as much smaller rate constant than the amorphous alloy. The rate controlling process for oxidation of crystalline Fe₄₀Ni₄₀P₁₄B₆ is diffusion of iron and nickel in the multiphase oxide layer, which consists of a fine scale mixture of NiO, Fe₃O₄, Fe₂O₃ and NiFe₂O₄, crystals. The difference in oxidation behaviour between amorphous and crystallized Fe₄₀Ni₄₀P₁₄B₆ is caused by the different alloy microstructures.