Kinetics of thermal devitrification (crystallization) of a titanium amorphous alloy

Thermal investigation, by differential scanning calorimetry, of the behaviour of an amorphous alloy (39 Cu, 8 Ni, 1 Si and 52 Ti, wt%) was undertaken in a hydrogen atmosphere. It was shown that crystallization (devitrification) proceeds through four different stages within the temperature range 673 to 853 K (400 to 580° C) and consequently four exothermal maxima at temperatures which depend on the heating programme are registered on the thermograms. The activation energies of each cyrstallization stage, the frequency factor, rate constant, half-time of the reaction and crystallization enthalpy, were determined. Particular attention is paid to a discussion of the crystallization process of each stage in correlation with the results obtained by X-ray analysis.     

Electro-spark deposition of Fe-based amorphous alloy coatings

A simple and effective surface coating technique, electro-spark deposition (ESD), has been used to produce amorphous alloy coatings. Fe-Cr-Mo-Gd-C-B amorphous alloy rods produced by copper mould casting were used as electrode to produce coatings onto 304 stainless steel substrate. Classical X-ray diffraction (XRD), glancing angle XRD (GAXRD), and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis indicate that the coatings have an average thickness of ∼ 30 μm, show an amorphous structure, and are metallurgically bonded to the substrate. Microhardness tests showed that the coating layer has a high hardness of 1542 kg/mm², implying a much improved wear resistance on surface of stainless steels.     

Fe基非晶合金粉末的研究进展

非晶合金粉末是指快冷雾化合金液滴所制得的合金粉末,其中Fe基非晶合金粉末因具有生产成本低廉和应用前景广阔等优势,一直备受青睐。同时,Fe基非晶合金粉末的应用也为块体Fe基非晶合金应用难的问题提供了一条崭新的途径。本文综述了Fe基非晶合金粉末的研究进展,对其在涂层制备、磁性材料、激光3D打印、废水处理4个方面的研究现状进行了归纳分类与总结,并分析了Fe基非晶合金粉末在各领域的应用优势。最后指出Fe基非晶合金粉末在制备高质量涂层、老化磁性粉末再利用及增材制造领域的研究方向,并展望了作为传感、控制等功能性器件的应用前景。此外,在薄膜等小尺寸、低维材料及柔性电子领域也展现出巨大的应用潜力。     

Induced crystallization of an amorphous Cu-Zr alloy

The crystallization behaviour of the amorphous Cu₆₀Zr₄₀ has been examined by simultaneous deformation and annealing, just below the crystallization temperature T_c. This treatment causes a heterogeneous nucleation and growth of small crystals, belonging to the Cu₁₀Zr₇ phase near the Cu₆₀Zr₄₀ composition. It was also found that subsequent annealing at temperatures $\text{T}\text{≤}\text{T}{}_{\mathrm{<mtext>c</mtext><mtext>?</mtext>}}$ does not accelerate the crystal growth, but results in a copious nucleation surrounding the single crystals.     

Enhancement of shear stability of a Fe-based amorphous alloy using electrodeposited Ni layers

Tensile and fracture behaviors of sandwich-structured composites consisting of a Fe-based amorphous layer with a constant thickness and ultrafine-grained Ni layers with different thicknesses were investigated. The results indicate that the initiation and the stable propagation of the shear band in the amorphous layer was dominated by the Ni layers due to their strong constraint role. The catastrophic fracture of the amorphous layer was postponed in the sandwich composites through properly increasing the constrained Ni layer thickness, which effectively decreased the shear stress on the shear fracture planes of the amorphous layer, and thus led to stable propagation of the primary SB characterized by the increase in the smooth region size of the shear band.     

Characterization of crystallization in amorphous 2605 SC alloy

The annealing characteristics, the crystallization sequence of precipitating phases and their geometry have been studied for the amorphous alloy 2605 SC through X-ray and reflection electron diffraction, scanning electron microscopy and field ion microscopy.The as-received samples were found to contain small domains of crystalline Fe₃Si, Fe₂₃(B, C)₆ and an oxide of iron (maghemite, Fe₃O₄) on the ribbon surfaces.Samples annealed at 673 K for 10, 50, 100 and 1000 min reveal that there is a sequential difference in the crystallization of the ribbon surfaces and the bulk, the latter exhibiting the nucleation of α-Fe first. Moreover, in situ (in an electron microscope) continuous annealing of the samples indicates that, although formation of ferrite crystals occurs in the bulk, the initial crystallizing phase on the surfaces is the f.c.c. Fe₂₃(B, C)₆. Heat treatment at temperatures above 773 K, however, is seen to produce similar phase consistency, and thus diffraction patterns, from both regions. These structures primarily are seen to be composed of a dendritic α-Fe and the Fe₂₃(B, C)₆ phases along with the as yet non-crystallized amorphous domains. The equilibrium Fe₂B phase is not observed at the annealing temperatures (above 923 K) used.     

Kinetics of devitrification (crystallization) of amorphous titanium

In this paper the behaviour of amorphous titanium (62.0% Ti, 25.0% Ni, 9.0% Cu and 4.0% Si) has been investigated by differential scanning calorimetry (DSC). It has been shown that the crystallization process takes place throughout three distinct stages within the temperature interval 713–788 K; three exothermic thermal effects, depending upon the heating rate have been noticed as well. It has also been proved that, at room temperature and in hydrogen atmosphere, amorphous titanium sorbs hydrogen and liberates the same at temperatures exceeding 473 K, showing an exothermic thermal effect. During the performed research, the activation energy of crystallization, a factor of frequency, rate constants, as well as a half-time of reaction and heat of crystallization, have been determined.     

连续压应力下Fe基非晶合金带材的压磁效应

通过对Fe基非晶合金带材连续施加压力,测试其附近闭合回路电感变化,研究了Fe基非晶合金带材的电感式压磁效应。结果表明,通过测试Fe基非晶合金带材附近闭合回路电感变化可用来测试和表征Fe基非晶合金带材的压磁性能;在f=1kHz时,Fe基非晶合金带材压磁性能稳定性好,随着压力的增大带材压磁性能升高,在同一压力情况下,Fe73.5Cu1Nb3Si13.5B9带材压磁性能优于Fe78Si9B13带材;在f=100kHz时,Fe73.5Cu1Nb3Si13.5B9带材压磁性能稳定性优于Fe78Si9B13带材,并且Fe73.5Cu1Nb3-Si13.5B9带材在f=1kHz、压应力为0.69MPa时具有最佳的压磁性能;在压应力<0.1MPa条件下,随着压应力增大,线圈电感值Ls有一个剧增的上升趋势,铁基非晶带材压磁性能对微小应力更加敏感。     

含Be多元合金非晶形成能力的替代效应研究

利用晶胞平移和分子动力学模拟建立了Zr4lTil3.8Be22.5Ni17.5Cu5．2晶态和非晶合金的原子结构模型，利用递归方法研究了Zr4lTi13.8Be22．5Ni17．5Cu5．2晶态及非晶态合金中元素的替代效应．Be与B、Al、Si状态密度形状相似表明Be与B、Al、Si具有相似的性质，可以用Al、B、Si代替Be；非晶态相对于晶态的结构能差表明，用Al、B、Si代替Be后均使合金的非晶形成能力下降，只是Al、B下降的幅度较小；用Al、B替代Be，再用其它过渡金属替代Cu、Ni或zr、Ti可使非晶形成能力达到含Be合金的水平．     

Zr对Pr-Fe-B非晶合金晶化形成纳米晶合金的作用

从非晶合金化激活能的角度，分析了Pr-Fe-B非晶合金在退火过程中晶粒粗大的原因，揭示了Zr元素在其晶化过程中的作用，结果表明，Zr能改变Pr-Fe-B非晶合金中α－Fe相的晶化行为，有助于形成尺寸细小的α-Fe相。     

Surface crystallization of amorphous Fe-B-Si alloy annealed in a gas atmosphere containing organic vapour

The relationship between the annealing atmosphere and the magnetic properties of Fe_78.5B₁₃Si_8.5 amorphous alloy has been studied, showing that annealing in an inert gas atmosphere containing a borosiloxane resin significantly improves the core loss of the amorphous ribbon, and that annealing in an inert gas without any organic resins, gives much better results than annealing in an inert gas atmosphere containing cellulose and vinyl acetate resins. A boron-depletion zone was detected by Auger electron spectroscopy under the oxide film formed during annealing in the inert gas atmosphere containing cellulose and vinyl acetate resins. Annealing of the amorphous ribbon in the cellulose and vinyl acetate resins selectively oxidizes boron in the alloy to form a B₂O₃ film and a boron depletion zone; the alloy in this zone is then crystallized into -Fe. This surface crystalline layer induces out-of-plane magnetic anisotropy in the amorphous ribbon and thus deterioration of the core loss. On the other hand, annealing in the borosiloxane resin results in neither selective oxidation of boron nor surface crystallization of the amorphous ribbon     

Studies on crystallization and domain structure of a ferromagnetic amorphous alloy Co90Zr10

The paper presents the first results of studies on crystallization and domain structure of a new ferromagnetic amorphous alloy Co₉₀Zr₁₀. Amorphous Co-Zr alloys were obtained by the piston and anvil method with 20 to 45 at% of Co and 90 at% of Co. Crystallization of Co₉₀Zr₁₀ was studied by X-ray diffraction and differential calorimetry, as well as by transmission electron microscopy (TEM) with simultaneous heating of the material. Domain structure in the amorphous phase was investigated by the method of Lorentz. The types of structures occurring were described, domain wall widths were calculated, and the direction of changes in the parameters of the magnetic structure — caused by annealing and phase transformation — was suggested.     

超音速火焰喷涂制备Fe基非晶合金涂层的组织与腐蚀性能研究

采用超音速火焰喷涂技术制备了Fe基非晶涂层,通过激光粒度分析仪、X射线衍射仪、扫描电子显微镜等测试技术对Fe基合金粉末以及获得的Fe基涂层的形貌和显微组织结构进行了研究,结果表明,采用合适的喷涂工艺可以获得非晶态的Fe基合金涂层。Fe基非晶合金涂层的耐腐蚀性实验表明,获得的非晶合金涂层具有优异的耐腐蚀性。     

Nanolamellar structure obtained by simple crystallization of an amorphous cobalt-based magnetic alloy

A novel modulated nanolamellar structure with a lamellar spacing of about 5 nm was obtained by simple heat treatment of an initially amorphous Co/sub 65/Si/sub 15/B/sub 14/Fe/sub 4/Ni/sub 2/ magnetic alloy. The crystallographic characteristics of this nanolamellar structure were investigated using selected area diffraction pattern, Kikuchi maps, convergent beam electron diffraction, and X-ray diffraction techniques. The crystal structure of the lamellae was found to be a novel phase with a C-base centered orthorhombic crystal structure of a=0.74 nm, b=1.07 nm, and c=0.77 nm, the nanolamellar structure was modulated along the (0 0 1) plane. High-resolution transmission electron microscopy observations showed negligible lattice mismatch between neighboring lamellae. Electron energy loss spectroscopy mapping showed a periodic variation of boron composition corresponding to the nanolamellar periodicity. The formation of the nanolamellar structure was found to be due to spinodal decomposition within the grains formed by crystallization of the alloy.