Zr48Cu45Al7大块金属玻璃的原子结构研究

应用同步辐射X射线衍射(XRD)和广延X射线吸收精细结构边方法(EXAFS),结合反蒙特卡罗(RMC)拟合、Voronoi分形技术等对Zr₅₀Cu₅₀二元和Zr₄₈Cu₄₅Al₇三元金属玻璃材料的微观结构进行了系统的研究.结果表明:ZrCuAl三元金属玻璃中Al原子与Zr原子、Cu原子之间存在强相互作用,表现为键长的明显缩短,导致其微观结构中的Voronoi团簇体积普遍小于Zr_{50关键词： 大块金属玻璃 原子结构 玻璃形成能力 同步辐射技术}     

铸锭凝固组织对相应非晶合金晶化过程中二十面体准晶相形成动力学的影响

通过在真空电弧熔炼炉内对合金铸锭进行反复熔炼处理，获得到了凝固组织不同的Zr₆₅Al_7.5Cu_12.5Ni₁₀Ag₅合金铸锭.在相同的制备条件下，由凝固组织不同的合金铸锭通过吸铸法制备得到了薄片非晶合金.利用差示扫描量热法(DSC)对非晶合金的晶化动力学进行了分析.x射线衍射谱表明，在Zr₆₅Al_7.5Cu_12.5Ni₁₀Ag₅非晶合金晶化过程中，二十面体准晶相(I相)作为初生相析出.Kissinger分析结果表明，合金铸锭的凝固组织细化，相对应的非晶合金发生晶化时，I相形成与分解的有效激活能都增大，说明非晶合金及析出的I相的热稳定性都提高.从结构的遗传性角度就合金铸锭凝固组织对相应非晶合金晶化过程中二十面体准晶相的形成动力学的影响进行了讨论. 关键词： 二十面体准晶相 晶化动力学 凝固组织     

Acid corrosion of amorphous and crystalline Cu-Zr alloys

Corrosion resistance of amorphous and crystalline Cu₄₅Zr₅₅, Cu₅₀Zr₅₀ and Cu₆₀Zr₄₀ alloys in strong acid (C_H⁺ = 1 M ℓ^-1) solutions was investigated with the use of potentiodynamic and gravimetric techniques. It was observed that the corrosion resistance of these alloys tested in H₂SO₄ and HNO₃ solutions was very high. However, amorphous Cu-Zr alloys exhibit a lack of resistance in HCl solutions where the corrosion rate increases with the rise of Cu content in the alloy (selective etching of Zr). Crystallization of alloys strongly improves their resistance to corrosion in HCl provided the Zr content in an alloy ⩾ 50 at%.     

μSR study of Cu10Zr7

It is shown that temperature dependences Λ(T) of dipole relaxation rate of the positive muon spin in crystalline and amorphous states of Cu₁₀Zr₇ are approximately the same over the temperature interval 20–300 K. this fact points out approximately identical close-order structure of crystalline and amorphous states of Cu₁₀Zr₇ alloy.     

Wear resistance of CuZr-based amorphous-forming alloys against bearing steel in 3.5% NaCl solution

Abstract

To investigate the amorphous-crystalline microstructure on the tribocorrosion of bulk metallic glasses (BMGs), 6 mm diameter rods of Cu_46-xZr₄₇Al₇Ag_x (x = 0, 2, 4) amorphous-forming alloys with in situ crystalline and amorphous phases were fabricated by arc-melting and Cu-mould casting. Using a pin-on-disc tribometer, the tribo-pair composed by CuZr-based amorphous-forming alloys and AISI 52100 steel were studied in 3.5% NaCl solution. With the increase of Ag content from 0 to 4 at.%, the compressive fracture strength and the average hardness decrease firstly and then increase. Moreover, 4 at.% Ag addition increases the amount of amorphous phase obviously and inhibits the formation of brittle crystalline phase, resulting in the improvement of corrosion resistance and the corrosive wear resistance. The primary wear mechanism of the BMG composites is abrasive wear accompanying with corrosive wear. The tribocorrosion mass loss of Cu₄₂Zr₄₇Al₇Ag₄ composite is 1.5 mg after 816.8 m sliding distance at 0.75 m s^?1 sliding velocity under 10 N load in NaCl solution. And the volume loss evaluated from the mass loss is about 20 times lower than that of AISI 304 SS. Thus, Cu₄₂Zr₄₇Al₇Ag₄ composite may be a good candidate in the tribology application under marine environment.     

Effect of Fe on the glass-forming ability,structure and devitrification behavior of Zr–Cu–Al bulk glass-forming alloys

We report on the glass-forming ability and devitrification behavior of Zr₆₀Cu₃₀Al₁₀, Zr₆₀Cu₂₅Al₁₀Fe₅ and Zr_62.5Cu_22.5Al₁₀Fe₅ bulk glass-forming alloys on heating. The effect of Fe addition on the structure of Zr–Al–Cu alloys is also discussed. Crystallization kinetics and structural changes in the glassy alloys were studied using X-ray diffraction, transmission electron microscopy, differential scanning and isothermal calorimetry methods. The results indicate that good glass-formers, such as Zr_62.5Cu_22.5Al₁₀Fe₅, are located somewhat beyond the equilibrium eutectic point. Possible phase separation in the supercooled liquid on heating and electron beam-induced in situ crystallization are observed and discussed.     

Manifestation of anharmonic localized vibrational modes in the specific heat and vibrational spectrum of freshly prepared amorphous alloys

The low-temperature specific heat of freshly prepared and annealed amorphous alloys Zr₇₀Be₃₀, Zr₆₇Cu₃₃, and Zr₇₅Rh₂₅ has been investigated experimentally. The integral parameters of the electronic and phonon spectra have been determined: the Sommerfeld coefficients and the Debye temperatures. Data from calorimetric and neutron experiments were compared on the basis of the theory of lattices with off-diagonal disorder and localized modes. It is concluded that a local rearrangement of the structure occurs in freshly prepared samples as the temperature decreases. A model of a bistable impurity configuration is proposed to explain this restructuring. Fiz. Tverd. Tela (St. Petersburg) 39, 145–152 (January 1997)     

Composition dependence of the electrical transport properties of amorphous transition metal alloys

Summary A quadratic composition dependence of the electrical resistivity of amorphous transition metal alloys has been investigated at room temperature. A very good agreement between the theoretical and the observed values has been obtained in the case of Ni_xZr_1−x and Cu_xZr_1−x for all compositions. The thermoelectric power was then correlated with the electrical resistivity satisfactorily for the Cu_xZr_1−x and Ni_xZr_1−x To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Surface tension measurement of metastable liquid Ti–Al–Nb alloys

Thermophysical properties of liquid alloys are usually difficult to measure, especially for high melting point and reactive alloys. In this work, the surface tensions of superheated and undercooled liquid Ti₅₅Al₄₅, Ti₅₀Al₄₅Nb₅ and Ti₄₅Al₄₅Nb₁₀ alloys are determined by using oscillating drop method under electromagnetic levitation state. The experimental results of Ti–Al and Ti–Al–Nb alloys display linear temperature dependence. The maximum undercoolings of 259 (0.143T _L), 268 (0.146T _L) and 275 K (0.147T _L) are respectively achieved for these three alloys. Furthermore, the viscosities of liquid Ti_55−x Al₄₅Nb _x alloys are also derived from the experimental results.     

Deformation behavior of Zr-based bulk metallic glass and composite in the supercooled liquid region

A Zr-based bulk metallic glass (BMG) with a composition of (Zr₇₅Cu₂₅)_78.5Ta₄Ni₁₀Al_7.5 and a bulk metallic glass matrix composite (BMGC) with a composition of (Zr₇₅Cu₂₅)_74.5Ta₈Ni₁₀Al_7.5 have been prepared by copper-mold casting. The compressive deformation behavior of the BMG and BMGC was investigated in the supercooled region at different temperatures and various strain rates ranging from 8×10⁻⁴ s⁻¹ to 8×10⁻² s⁻¹. It was found that both the strain rate and test temperature significantly affect the deformation behavior of the two alloys. The deformation follows Newtonian flow at low strain rates but non-Newtonian flow at high strain rates. The deformation mechanism for the two kinds of alloys was discussed in terms of the transition state theory. Supported by the National Natural Science Foundation of China (grant Nos. 50471060 and 50635020)     

Thermopower of some amorphous transition metal-alloys

Measurements of the thermopower for amorphous alloys are reported in the temperature range 77K to 320K. The alloys examined are Cu₅₀Ti₅₀, Pd₈₀Si₂₀, Pd₃₀Zr₇₀ and Cu₄₀Zr₆₀. The data are compared with values of similar systems, as far as available. In addition we analyse the temperature coefficient of the thermopower, applying a model, based on the Ziman formulation of the transport properties.     

Structural features and the microscopic dynamics of the three-component Zr<Subscript>47</Subscript>Cu<Subscript>46</Subscript>Al<Subscript>7</Subscript> system: Equilibrium melt,supercooled melt,and amorphous alloy

The structural and dynamic properties of the three-component Zr₄₇Cu₄₆Al₇ system are subjected to a molecular dynamics simulation in the temperature range T = 250–3000 K at a pressure p = 1.0 bar. The temperature dependences of the Wendt–Abraham parameter and the translation order parameter are used to determine the glass transition temperature in the Zr₄₇Cu₄₆Al₇ system, which is found to be T_c ≈ 750 K. It is found that the bulk amorphous Zr₄₇Cu₄₆Al₇ alloy contains localized regions with an ordered atomic structures. Cluster analysis of configuration simulation data reveals the existence of quasi-icosahedral clusters in amorphous metallic Zr–Cu–Al alloys. The spectral densities of time radial distribution functions of the longitudinal (C?_L(k, ω)) and transverse (C?_T(k, ω)) fluxes are calculated in a wide wavenumber range in order to study the mechanisms of formation of atomic collective excitations in the Zr₄₇Cu₄₆Al₇ system. It was found that a linear combination of three Gaussian functions is sufficient to reproduce the (C?_L(k, ω)) spectra, whereas at least four Gaussian contributions are necessary to exactly describe the (C?_T(k, ω)) spectra of the supercooled melt and the amorphous metallic alloy. It is shown that the collective atomic excitations in the equilibrium melt at T = 3000 K and in the amorphous metallic alloy at T = 250 K are characterized by two dispersion acoustic-like branches related with longitudinal and transverse polarizations.     

Investigation of short‐range structural order in Zr69.5Cu12Ni11Al7.5 and Zr41.5Ti41.5Ni17 glasses,using X‐ray absorption spectroscopy and ab initio molecular dynamics simulations

Short‐range order has been investigated in Zr_69.5Cu₁₂Ni₁₁Al_7.5 and Zr_41.5Ti_41.5Ni₁₇ metallic glasses using X‐ray absorption spectroscopy and ab initio molecular dynamics simulations. While both of these alloys are good glass formers, there is a difference in their glass‐forming abilities (Zr_41.5Ti_41.5Ni₁₇ > Zr_69.5Cu₁₂Ni₁₁Al_7.5). This difference is explained by inciting the relative importance of strong chemical order, icosahedral content, cluster symmetry and configuration diversity.     

The electrical resistivity of amorphous alloys at low temperatures

Measurements of the temperature- and magnetic field dependence of the electrical resistance of some metallic glasses are presented. The data obtained for Cu₅₇Zr₄₃, Cu₄₀Zr₆₀ and Pd₃₀Zr₇₀ demonstrate that deviations from the high temperature behaviour extrapolated to low temperatures are caused by superconducting effects. The paraconductivity which is strongly enhanced in amorphous alloys is shown to agree quite well with theoretical models. The normal state resistance does not saturate down to temperatures of about 2 K. It still exhibits a negative temperature coefficient of the resistivity.     

Research on Zr50Al15−xNi10Cu25Yx amorphous alloys prepared by mechanical alloying with commercial pure element powders

Amorphous Zr₅₀Al_15−xNi₁₀Cu₂₅Y_x alloy powders were fabricated by mechanical alloying at low vacuum with commercial pure element powders. The effects on glass forming ability of Al partial substituted by Y in Zr₅₀Al₁₅Ni₁₀Cu₂₅ and thermal stability of Si₃N₄ powders addition were investigated. The as-milled powders were characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimeter. The results show that partial substitution of Al can improve the glass forming ability of Zr₅₀Al₁₅Ni₁₀Cu₂₅ alloy. Minor Si₃N₄ additions raise the crystallization activation energy of the amorphous phase and thus improve its thermal stability.     

非晶态Cu56Zr44合金的结构及其等温退火晶化过程的研究

利用X射线衍射技术、差示扫描量热分析技术和透射电子显微镜研究了非晶态Cu₅₆Zr₄₄合金的结构及其等温退火条件下的晶化过程.实验结果表明,非晶态Cu₅₆Zr₄₄合金在室温下的短程结构类似于硬球无规密堆积分布.在703K过冷液相区内等温退火时发现,当退火时间为3min时,晶化产物主要为Cu₈Zr₃相;当退火时间为6min时,Cu₈Zr₃关键词： 非晶态 56Zr₄₄合金')" href="#">Cu₅₆Zr₄₄合金 结构 等温退火     

Effects of nickel on the crystallization of Zr70Cu20Ni10 amorphous alloy

Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) are employed to investigate the effects of nickel on the crystallization of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy. We have found that the crystallization process of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy is strongly influenced by the addition of nickel. Addition of 10 at% Ni to the Zr₇₀Cu₃₀ amorphous alloy makes the crystallization process proceed from a single-stage mode to a double-stage mode. The activation energy for crystallization of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy is calculated to be about 388kJ·mol^-1 on the basis of the Kissinger equation. The effects of nickel on the crystallization of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy are discussed in terms of the genetics of metals.     

Magnetic interference effect in amorphous D-band metals with high electrical resistivity

Systematic occurence of low temperature resistivity anomalies (upturn) in amorphous alloys Zr₅₀Cu₅₀, Zr₇₅Ni₂₅, and Y₇₅A?₂₅ containing up to 4 at .% Gd is observed. Detailed analysis of ‘background’ impurity (other than Gd) effects on the electrical resistivity of the alloy host Zr₅₀Cu₅₀ provides unambiguous evidence that the anomalies are due solely to the Gd ions. The present results are interpreted in terms of conduction electrons with short mean free path scattering from nearest neighboring pairs of Gd spins. Predictions derived from the diffraction type model of magnetic interference, however, fail to describe all the results on metals with high electrical resistivity. Data on Zr₅₀Cu₅₀ containing Fe and Mn are also discussed.     

Nonlinear elastic characteristics of Zr52.5Ti5Cu17.9Ni14.6Al10 and Pd40Cu30Ni10P20 bulk metallic glasses

The influence of uniaxial compression on the propagation of sound in Zr_52.5Ti₅Cu_17.9Ni_14.6Al₁₀ and Pd₄₀Cu₃₀Ni₁₀P₂₀ bulk metallic glasses is investigated, and the third-order elastic moduli of these glasses are determined. __________ Translated from Fizika Tverdogo Tela, Vol. 47, No. 3, 2005, pp. 395–399. Original Russian Text Copyright ? 2005 by Kobelev, Kolyvanov, Khonik.