Thermal stability data of amorphous binary alloys

Data on the thermal stability of amorphous (glassy) binary alloys are compiled. Where available, alloy preparation method, crystallization temperature and method of measurement of crystallization temperature are tabulated. Other relevant aspects such as crystallized phases and compositions, glass transition temperature and analytical parameter variations also are given when data are available.     

Formation of amorphous phase in the binary Cu−Zr alloy system

The aim of this work is to elucidate the formation of the amorphous phase in the Cu−Zr binary alloy system. It was found that 1 mm diameter rods with a fully amorphous structure can be prepared in a relatively wide range of compositions. In contrast, the formation of 2 mm diameter rods was achieved only for the Cu₆₄Zr₃₆ alloy and in the range of Cu₅₃Zr₄₇−Cu₅₀Zr₅₀, which are compositions near the energetically stable Cu₂Zr and CuZr intermetallic compounds. The difference between the calculated Gibbs free energy of the amorphous phase and the intermetallic compounds gives insight into the range of glass formation. In addition, the formation of the energetically stable phases can be kinetically by-passed owing to the crystallization of several competing phases.     

Copper corrosion mitigation by binary inhibitor compositions of potassium sorbate and benzotriazole

This work presents the combined effect of two inhibitors, potassium sorbate (2,4-hexadienoic acid potassium salt) and 1,2,3-benzotriazole, on the corrosion behavior of copper in sulfate based solutions. Individual and combined characteristics of copper corrosion inhibition in sulfate solution in the presence of potassium sorbate (K-sorbate) and benzotriazole (BTAH) were studied with the use of electrochemical, microscopic and spectroscopic methods. Whereas, BTAH alone protects copper from corrosion attack in sulfate solutions only in a limited potential range below 0.4 V vs. saturated calomel electrode (SCE), the presence of K-sorbate combined with BTAH in such solutions enables the protection of the copper surface at potentials above 0.4 V_SCE. The mixture of both inhibitors provides supplementary and robust corrosion protection of Cu over a wide potential range.     

Phase diagrams of nanometer-sized particles in binary systems

A study on alloy phase formation in nanometer-sized particles by insitu transmission-electron microscopy revealed that the phase equilibrium of these particles is significantly different from that of the corresponding bulk materials. A theoretical study was conducted based on thermodynamics modified so that Gibbs free energies for bulk materials available in the CALPHAD database were modified by taking into consideration factors affecting the phase equilibrium of nanometer-sized alloy particles. The study proved useful to evaluate the results obtained from experiments. For more information, contact Junggoo Lee, Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871, Japan; +81-6-6879-7941; fax +81-6-6879-7942; e-mail; jg-lee@uhvem.osakau.ac.jp.     

Energetic characteristics of the adsorption of oxygen on surfaces of polycrystalline and amorphous aluminum-cerium alloy

Based on modeling the optical-conductivity spectrum estimated from the data of optical experiments, the electronic structure of nonoxidized and oxidized surfaces of liquid, amorphous, and polycrystalline Al-8 at % Ce alloy is studied. The conduction band of the alloy in the liquid and amorphous states is found to be split. In the polycrystalline state, there is no splitting. The heat of adsorption of oxygen on the alloy surface is calculated for amorphous and polycrystalline alloy states.     

Excellent magneto-caloric effect of a binary Gd63Ni37 amorphous alloy

In the present work, we reported an excellent magneto-caloric effect (MCE) of a binary Gd₆₃Ni₃₇ amorphous alloy. The amorphous features of the Gd₆₃Ni₃₇ as-spun ribbons were ascertained by their X-ray diffraction pattern, differential scanning calorimetry (DSC) curve and their magneto-caloric behaviors. The Gd₆₃Ni₃₇ amorphous ribbon exhibits rather high magnetic entropy change peak (−ΔS_m^peak), refrigeration capacity (RC) and adiabatic temperature rise (ΔT_ad). The binary Gd₆₃Ni₃₇ amorphous alloy is expected to play an important role in developing high performance multi-component Gd-Ni-based amorphous magnetic refrigerants.     

无损精确定量测量二元合金成分探讨

采用三种成分分析方法定量测量了二元Ni-W合金试样的成分变化区.三种方法分别为密度转换成分法、微观组织转换成分法和X射线荧光光谱分析(XRF).对比三种分析方法测得的数据表明,密度转换成分法和微观组织转换成分法都能够精确地测定合金成分,而其中微观组织转换成分法还可以在保持试样完整的情况下得到测试结果.     

Thermodynamic interdiffusion coefficient in binary systems with intermediate phases

A new form of diffusion coefficient, termed the thermodynamic interdiffusion coefficient has been introduced in this investigation; it is related to the conventional chemical interdiffusion coefficient and thermodynamic properties of the system. Three main advantages in using the thermodynamic interdiffusion coefficient are described by applying this alternative approach of diffusion analysis, as an example, to the Al–Ni system. These include (1) a better interpretation of the relative diffusivities in the different phases of the same system, (2) estimation of appropriate values of the activation energy of the diffusion process and (3) determination of the thermodynamic intrinsic diffusion coefficient (also known as the tracer diffusion coefficient) in an intermediate phase with narrow homogeneity range, which otherwise is not possible without tracer diffusion experiments.     

Mechanical properties of amorphous and polycrystalline multilayer systems

Amorphous and polycrystalline multilayer structures containing materials with metallic (Cr, Cr₃C₂), ionic (Al₂O₃) and covalent (SiC) bonding have been prepared by magnetron sputtering and ion plating in a dual-source apparatus. Up to 1000 layers have been deposited with a constant total thickness of 2.3 μm.

Below a single-layer thickness of 10–30 nm the mechanical properties stress and hardness show strong variations. On one hand it is possible that below a certain thickness the mechanical properties of a single layer change (A. Pan and J.E. Greene, Thin Solid Films, 78 (1981) 25–34). On the other hand electrical resistance and electron spin density measurements indicate that electronic effects may be involved. An attempt is made to explain the observed correlations by transport mechanisms of the electrons, by saturation of dangling bonds with delocalized electrons and by changes in the electronic band structure.     

Compilation of thermodynamic and phase information for the binary systems of molybdenum

The publication of the computation of molybdenum data has prompted a number of questions about the motivation for the project and general philosophy used in evaluating data. This article presents some general comments about the project and about the format of the compilations.     

Thermochemical investigation of binary liquid mixtures in glass-forming oxide systems

Methods and equipment successfully employed in high- temperature calorimetry to measure partial and integral enthalpies of mixing in liquid oxide systems are reviewed with special attention given to the drop-mixing method. This technique has been used to measure enthalpies of mixing in binary liq-uid mixtures composed of network forming oxides (e.g. SiO₂) and network modifying oxides (e.g. Na₂O). Results for the systems Na₂O-SiO₂ and Na₂O- B₂O₃ are presented graphically. Entropies of mixing were estimated by combining enthalpies with available data on Gibbs energies of mixing. Prominent thermochemical features of glass-forming oxide melts are pointed out. The observed thermodynamic behavior is discussed in relation to its structural basis.     

Solid state amorphisation in binary systems prepared by mechanical alloying

In the present work a detailed study of amorphisation in different systems prepared by mechanical alloying under the same experimental conditions was carried out, milling up to 50 and 100 h in some cases. The systems studied were: AlTi, AlNi, AlFe, FeNi, FeCo, NiMo, NiW, NiCo, MoW, CoMo. These systems were chosen to study the effect of Al-transition metal, transition metal–transition metal and also systems with large and small negative heat of mixing, different and similar crystal structures, atomic sizes and diffusion coefficients. Calculations based on the Miedema model for alloy formation and amorphisation on all the alloys studied were performed. The experimental results from X-ray diffraction and transmission electron microscopy showed that the systems based on Fe (FeNi, FeCo and FeAl) did not amorphised, even after milling for 100 h, and formed a stable solid solution with a nanometric grain size of 7 nm. The systems NiMo, NiW, MoW and CoMo (systems with small negative heat of mixing), showed amorphisation after 50 h of milling. NiAl and TiAl form an intermediate amorphous phase after around 20 h of milling and with further milling they recrystallize into a fcc solid solution. Agreement between the theoretical calculations based on the Miedema model and the experimental results was found in most of the systems.     

Thermochemical investigation of binary liquid mixtures in glass-forming oxide systems

Methods and equipment successfully employed in high- temperature calorimetry to measure partial and integral enthalpies of mixing in liquid oxide systems are reviewed with special attention given to the drop-mixing method. This technique has been used to measure enthalpies of mixing in binary liq-uid mixtures composed of network forming oxides (e.g. SiO₂) and network modifying oxides (e.g. Na₂O). Results for the systems Na₂O-SiO₂ and Na₂O- B₂O₃ are presented graphically. Entropies of mixing were estimated by combining enthalpies with available data on Gibbs energies of mixing. Prominent thermochemical features of glass-forming oxide melts are pointed out. The observed thermodynamic behavior is discussed in relation to its structural basis.     

RE-X二元合金相图的热力学数据库

利用CALPHAD方法,采用亚正规溶体模型、亚点阵模型以及理想气体模型来描述RE-X(Ag,Bi,Cr,Mn,Mo,V,Zn)中二元系各相的Gibbs自由能,并结合相平衡及热力学性质的实验结果,对Ag-RE(RE:Sc,Y Nd,Sm,Gd,.Tb,Ho,Er)、Bi-RE(RE:Nd,Tm,Er,Ho,Pr,Gd)、...     

Osmotic convection-driven instability and cellular eutectic growth in binary systems

Using phase-field theory we demonstrate that osmotic stress may result in intense convection in solidifying eutectic systems. Under isothermal conditions the natural convection is of osmotic origin, and driven by the non-equilibrium composition field. Osmotic forces arise mostly in the interface layer, since large concentration gradients are localized near the triple junctions of the phases. Tuning friction forces at the solid-liquid interface controls the intensity of fluid flow. We have found that convection in the low friction regime significantly affects microstructural pattern formation. Osmotic convection-driven instability of the solid-liquid interface is observed that leads to cellular and dendritic eutectic crystal growth. The mechanism we propose is distinct from diffusive instability that is widely acknowledged as the main cause of cellular and fingerlike patterns.     

Ni基高温合金共格强化相平衡形状的能量分析

采用三维有限元方法计算了不同形状因子的γ’强化相在基体为γ相的Ni基高温合金中引起的弹性应变能密度,进而建立了以形状因子为变量的弹性应变能密度表达式。通过最小化γ’强化相引起的弹性应变能和界面能之和,得到了γ’强化相的平衡形状与其特征半径之间的函数关系。本文的分析很好地解释了文献报道的Ni基高温合金中γ’强化相形状演变的实验规律,结果表明:通过三维有限元法结合强化相粒子形状近似法计算模型,可以给出复杂情况下强化相粒子引起的弹性应变能密度的表达式,并有效地应用于材料共格相变的热力学研究。