Diffusion of Au and Cu in amorphous Fe80B20 and Fe82B18 alloys

Diffusion rates (D) of Au in two amorphous alloys, Fe₈₀B₂₀ and Fe₈₂B₁₈, and of Cu in amorphous Fe₈₂B₁₈ alloy were measured in the temperature range 546–645 K by using the technique of Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES), respectively. The diffusion of Au was found to be 3 to 6 times faster in Fe₈₀B₂₀ than in Fe₈₂B₁₈, though both the alloys had almost similar crystallization temperatures. The observed differences in the diffusion rates corroborate the fact that Fe₈₀B₂₀ has a more open structure than Fe₈₂B₁₈ as revealed from the reported values of the metal packing fractions of these two alloys. Also, the diffusivities of smaller sized Cu atoms (radius: 0.128 nm) were found to be higher by more than an order of magnitude than those of larger sized Au atoms (radius: 0.146 nm), suggesting a dependence ofD on the size of the diffusing species.     

非晶Fe82Si5B13合金的磁导率驰豫

在0—300℃范围内考查了非晶Fe₈₂Si₅B₁₃合金的磁导率等温弛豫动力学行为,给出了等时弛豫谱,观察到四个弛豫峰。测量表明,总的磁导率弛豫由两种弛豫过程组成,即对于退磁可逆的普通减落和对于退磁不可逆的磁导率连续衰减。计算了弛豫时间和激活能的分布,表明弛豫时间和激活能有宽的分布。普通减落和磁导率衰减过程的最可几激活能分别为1.0eV和1.4eV。对退火的样品,观察到磁导率先是增大而后是衰减的广义cross-over效应。 关键词：     

Magnetism in disordered magnetic Fe82−xNixCr18

The zero field μSR-method has been used to study the magnetism in the disordered magnetic alloy Fe_82−xNi_xCr₁₈ near the three-critical, pointx=25. The dynamic and static local field distributions are analyzed. The difference between spin-glass states obtained either from the paramagnetic or after the double transition is discussed.     

高压下非晶Fe82Si4B14合金的晶化

研究高压对非晶Fe₈₂Si₄B₁₄合金晶化过程的影响,给出常压下与77kbar下的时间-温度-变态图(即T-T-T图)。结果表明:合金晶化温度的压力梯度值随晶化进行的时间长短而改变。常压下晶化时,bcc-Fe(Si)固溶体相先形成;77kbar下晶化时,DOe型Fe₃B与bcc-Fe(Si)固溶体相同时出现。 关键词：     

Effect of silicon additions on the magnetic properties of Nd2Fe12Co2B alloy

The results of magnetic measurements performed on Nd₂Fe_12−xSi_xCo₂B alloys with 0⩽x⩽0.6 are presented. All the compound studied crystallize in the tetragonal Nd₂Fe₁₄B structure. The unit cell volume is found to decrease by introducing Si. With substitution of Fe by Si, the saturation moments decrease, but theanisotropy fields and Curie temperatures are found to increase significantly. For example, in Nd₂Fe_11.5Si_0.5Co₂b, at room temperature, μ_s=28.4μ_B, H_A=80 kOe and T_c=736 K.     

Nanocrystallization process and ferromagnetic properties of amorphous (Fe0.99Mo0.01)78Si9B13 ribbons

The nanocrystallization process of soft ferromagnetic (Fe_0.99Mo_0.01)₇₈Si₉B₁₃ ribbons has been studied in detail. Microstructural and ferromagnetic properties are examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy (MS), differential scanning calorimetry (DSC) and magnetization measurements. The Curie and crystallization temperatures are determined to be T_C=665 K and T_x=750 K, respectively. The T_x value is in well agreement with DSC measurement results. XRD patterns had shown two metastable phases (Fe₂₃B₆, Fe₃B) which were formed under in situ nanocrystallization process. These metastable phases embedded in the amorphous matrix have a significant effect on magnetic ordering. The ultimate nanocrystalline (NC) phases of α-Fe(Mo, Si) and Fe₂B at optimum annealing temperature had been observed respectively. It is notable that the magnetization of the amorphous phase decreases more rapidly with increasing temperature than those of NC ferromagnetism, which suggest the presence of the distribution of exchange interaction in the amorphous phase or high metalloid contents.     

The magnetic phase diagram of amorphous FexPd82−xSi18, 2⩽x⩽25

The magnetic phase diagram of the metallic glasses Fe_xPd_82?xSi₁₈, 2?x?25, is presented. Transitions from spin glass to weak ferromagnetism with composition and temperature are associated with the composition dependent heterogeneity of the rapidly quenched materials.     

Structure of α-FeSi alloys with 8 and 10 at % silicon

The atomic structure of single-crystal samples of Fe_{1 ? x} Si _x (x = 0.08, 0.10) alloys has been investigated using X-ray diffraction. It has been shown that the body-centered cubic (BCC) lattice of these alloys contain clusters with local ordering of the B2 type, which are characteristic of alloys with depleted composition (x = 0.05?0.06). The Fe₃Si phase with the D0₃ structure has been revealed at silicon concentrations x = 0.08 and 0.10. The volume fraction of Fe₃Si-phase regions increases both with an increase in the silicon concentration in the Fe_{1 ? x} Si _x alloy and during annealing of the samples with this silicon concentration at a temperature of 450°C. Based on the results obtained, it has been concluded that the anisotropic distribution of the B2 clusters, which arises as a result of thermomagnetic or thermomechanical treatment, is responsible for the induction and stability of the uniaxial magnetic anisotropy in the Fe_{1 ? x} Si _x (x = 0.05?0.10) alloys.     

High Bs nanocrystalline Fe84−x−yCuxNbySi4B12 alloys (x=0.0-1.4, y=0.0-2.5)

In this study, Cu and Nb content dependences of magnetic properties for annealed Fe_84−x−yCu_xNb_ySi₄B₁₂ alloy ribbons fabricated by melt spinning were investigated. In Fe_83−xCu_xNb₁Si₄B₁₂ alloy systems, the coercivity H_c markedly decreases with increasing x and exhibits a minimum at around x=1.0-1.2, while the saturation magnetic flux density B_s shows a slight variation. In Fe_83−yCu₁Nb_ySi₄B₁₂ alloy systems, H_c markedly decreases at around y=0.5, while B_s shows a monotonic decrease. Fe₈₂Cu₁Nb₁Si₄B₁₂ nanocrystalline alloy ribbons exhibit a high B_s of 1.78 T and a low H_c of 3.2 A/m. The core losses of the present alloys at 1.0 T at 400 Hz, P_10/400, and at 1.0 T at 1 kHz, P_10/1k, are 1.3 and 4.4 W/kg, respectively.     

金属玻璃(Fe0.8Ni0.15Cr0.05)78Si8B14的起始磁导率减落现象

在77—553K范围内的不同温度下测量了金属玻璃(Fe_0.8Ni_0.15,Cr_0.05)₇₈Si₈B₁₄的起始磁导率减落。测量结果表明,减落的温度关系表现为一个具有单一弛豫峰的不对称谱。在273K下考察了减落的动力学行为。用Hesse-Rubartsch方法拟合动力学曲线得到一个左右不对称的单峰激活能谱,最可几激活能大约为1.40eV。考察了减落的退火效应及退火动力学行为,结果表明,在宽的温度范围内,减落呈现明显的退火效应,而且退火动力学行为近似服从lnt动力学。 关键词：     

Mössbauer effect and NMR study of amorphous Ni80−x Fe x B16Si4

The magnetic phase diagram of amorphous Ni₈₀? _x Fe _x B₁₆Si₄ was studied by de-magnetization measurement, by⁵⁷Fe-Mössbauer spectroscopy and pulsed spin echo NMR.     

用X射线异常色散效应测定二元非晶合金Fe82B18偏径向分布函数方法的简化

本文采用Mo,Cu,Co三种不同波长的X射线辐射,测定了Fe₈₂B₁₈二元非晶合金的径向分布函数。比较了不同波长辐射对测定径向分布函数的影响。应用X射线异常色散方法计算了Fe₈₂B₁₈二元非晶合金的偏径向分布函数。在计算时略去了B-B原子对对径向分布函数的贡献,因而简化了计算过程,并相对提高了计算精度。所得结果与国际上使用同类方法或其它方法的结果相近。 关键词：     

Demagnetisation effects in Fe3-xMnxSi alloys

Low field de susceptibility measurements have been made on an Fe_3-xMn_xSi alloy with x = 1.14. The observed and calculated results show a demagnetising effect to be occuring in and around the ferromagnetic regime. This brings into question earlier assertions of spin-glass or micromagnet like properties and the critical exponent estimates for these alloys because they lie within the region of significant demagnetisation.     

Glass formation and magnetic properties of Fe-C-Si-B-P-(Cr-Al-Co) bulk metallic glasses fabricated using industrial raw materials

Formation of Fe-C-Si-B-P-(Cr-Al-Co) bulk metallic glasses with enhanced glass-forming ability (GFA) and magnetic properties fabricated using industrial pig-iron and Fe-P alloys as raw materials has been studied. It was found that GFA of the pig-iron (Fe_79.5C_18.0Si_2.3P_0.2, at%) could be improved by proper additions of only metalloids C, Si, P and B, and fully glassy structure was obtained in the Fe_75.5C_7.0Si_3.3B_5.5P_8.7 alloy with a critical diameter of 1 mm. With suitable additions of metallic elements Cr, Co and Al, the GFA is further increased and fully amorphous rods in 4 mm diameter can be prepared for the Fe_68.2C_7.0Si_3.3B_5.5P_8.7Cr_2.3Al_2.0Co_3.0 alloy that shows a unique combination of good soft-magnetic properties (M_s=1.03 T, H_c=9.39 A/m), high GFA and high fracture strength. These low-cost Fe-based bulk metallic glasses fabricated using industrial raw materials have a potential to be utilized as engineering materials.     

Vickers Microhardness and Hyperfine Magnetic Field Variations of Heat Treated Amorphous Fe78Si9B13 Alloy Ribbons

Amorphous Fe₇₈Si₉B₁₃ alloy ribbons were heat treated between 296 and 763 K, using heating rates between 1 and 4.5 K/min. Whereas one ribbon partially crystallized at T _x = 722 K, the other one partially crystallized at T _x = 763 K. The partially crystallized ribbon at 722 K, heat treated using a triangular form for the heating and cooling rates, was substantially less fragile than the partially crystallized at 763 K where a tooth saw form for the heating and cooling rates was used. Vickers microhardness and hyperfine magnetic field values behaved almost concomitantly between 296 and 673 K. The Mössbauer spectral line widths of the heat-treated ribbons decreased continuously from 296 to 500 K, suggesting stress relief in this temperature range where the Vickers microhardness did not increase. At 523 K the line width decreased further but the microhardness increased substantially. After 523 K the line width behave in an oscillating form as well as the microhardness, indicating other structural changes in addition to the stress relief. Finally, positron lifetime data showed that both inner part and surface of Fe₇₈Si₉B₁₃ alloy ribbons were affected distinctly. Variations on the surface may be the cause of some of the high Vickers microhardness values measured in the amorphous state.     

Detailed study of ultra-soft magnetic properties of Fe74Cu0.8Nb2.7Si15.5B7

The magnetic properties of nanocrystalline Fe₇₄Cu_0.8Nb_2.7Si_15.5B₇ alloy, which were rapidly solidified and then annealed at various temperatures between 475 and 650°C for different holding time, have been studied. Grain size, silicon content and the lattice parameter of α-Fe(Si) nanograins at the annealing temperatures were determined. Curie temperature of the amorphous phase was determined from the temperature dependence of permeability. For higher annealing temperatures and times, some Si diffused out of the α-Fe(Si) phase and formed an ordered DO₃ phase of Fe₃Si. This changed the overall magnetostriction and average anisotropy of the matrix, which deteriorated the magnetic softness of the material at higher annealing temperatures. Ultra-soft magnetic properties were achieved by averaging the random anisotropy via exchange interaction. Hysteresis loops for samples in as-cast and annealed conditions have also been studied.     

预注入对Si1-xCx合金形成的影响

室温下在单晶Si中注入(0.6—1.5)at%的C原子,部分样品在C离子注入之前在其中注入²⁹Si⁺离子产生损伤,然后在相同条件下利用高温退火固相外延了Si_1-xC_x合金,研究了预注入对Si_1-xC_x合金形成的影响.如果注入C离子的剂量小于引起Si非晶化的剂量,在950℃退火过程中注入产生的损伤缺陷容易与C原子结合形成缺陷团簇,难于形成Si_1-xC关键词： 离子注入 固相外延 1-xC_x合金')" href="#">Si_1-xC_x合金     

Investigation of X-ray diffraction and positron life times in Fe78Si9B13 alloys of amorphous and crystalline structures before and after hydriding

Measurements of mean positron life-times and X-ray diffraction were carried out in unhydrided alloys Fe₇₈Si₉B₁₃ of amorphous and crystalline structures, and after hydriding them. The process of hydriding was carried out at a pressure of 55.773 × 10⁵ N/m². during 168 h. The crystalline samples were obtained after annealing the amorphous alloy Fe₇₈Si₉B₁₃ at 673, 773 and 873 K, respectively. The results obtained after the hydriding process suggest thatan additional electron energy band is formed due to introducing hydrogen inside the samples. The annealing process shows that there exists a nonmonotonic relation between the concentration of free electrons and the degree of order to the structure.     

Recoilless fraction, structural, magnetic and thermal properties of Fe73.5Cu1Nb3Si13.5B9 alloy

Differential scanning calorimetry, X-ray diffraction and room temperature Mössbauer spectrum measurements of Fe_73.5Cu₁Nb₃Si_13.5B₉ (Finemet) alloy have been carried out in order to study its structural and magnetic properties as a function of annealing temperature. The DSC profile of as-quenched Finemet showed two exothermic peaks at 530 and 702 °C, corresponding to two crystallization processes. The Finemet alloy remains amorphous at 450 °C with one broad peak in XRD pattern and one broad sextet in Mössbauer spectrum. When the Finemet alloy was annealed at 550 °C, only well indexed body-center-cubic phase was detected. After being annealed at 650 and 750 °C, the XRD patterns showed the coexistence of α-Fe(Si) and Fe-B intermetallic phases with the increase in XRD peak intensities, indicating the growth of crystallites and the decomposition of Fe_73.5Cu₁Nb₃Si_13.5B₉ alloy at elevated temperatures. The Mössbauer spectra of annealed Finemet alloy could be fitted with 4 or 5 sextets and one doublet at higher annealing temperatures, revealing the appearance of different crystalline phases corresponding to the different Fe sites above the crystallization temperature. The appearance of the nanocrystalline phases at different annealing temperatures was further confirmed by the recoilless fraction measurements.     

The effect of Si content on the martensitic transfor-mation temperature of Ni55.5e18Ga26.5-xSix alloys

This paper investigates the effects of substitution of Si for Ga on the martensitic transformation behaviours in Ni-Fe-Ga alloys by using optical metallographic microscope and differential scanning calorimetry (DSC) methods. The structure type of Ni_55.5Fe₁₈Ga_26.5-xSi_x alloys is determined by x-ray diffraction (XRD), and the XRD patterns show the microstructure of Ni-Fe-Ga-Si alloys transformed from body-centred tetragonal martensite (with Si content x = 0) to body-centred cubic austenite (with x = 2) at room temperature. The martensitic transformation temperatures of the Ni_55.5Fe₁₈Ga_26.5-xSi_x alloys decrease almost linearly with increasing Si content in the Si content range of x ≤ 3. Thermal treatment also plays an important role on martensitic transformation temperatures in the Ni-Fe-Ga-Si alloy. The valence electronic concentrations, size factor, L2₁ degree of order and strength of parent phase influence the martensitic transformation temperatures of the Ni-Fe-Ga-Si alloys. An understanding of the relationship between martensitic transformation temperatures and Si content will be significant for designing an appropriate Ni-Fe-Ga-Si alloy for a specific application at a given temperature.