Rules for maximum solid solubility of transition metals in Ti,Zr and Hf solvents

1　INTRODUCTIONThemaximumsolidsolubility (Cmax)ofasolutemetalinasolventmetalrestrictstheadjustablerangeofcomponentsinanalloy .Itisveryimportantforstudyingnewalloysornewheattreatmentmethods .Vanadium basedsolidsolutionalloysareveryattrac tivehydrogenstoragematerials .Thistriggeredscien tiststoinvestigatesolidsolutionalloysforhydrogenstorage .TisubgroupbasedalloysadjacenttoV basedonesinPeriodicTableareassociatedwithsolidsolu tionhydrogen storagematerialsandthiswillbein structivefordevelop…     

Maximum solid solubility of transition metals in vanadium solvent

Maximum solid solubility （Cmax） of different transition metals in metal solvent can be described by a semi-empirical equation using function Zf that contains electronegativity difference, atomic diameter and electron concentration. The relation between Cmax and these parameters of transition metals in vanadium solvent was studied. It is shown that the relation of Cmax and function Zf can be expressed as In Cmax = Zf = 7. 316 5- 2. 780 5 （△X）^2- 71. 278δ^2-0. 855 56n^2/3. The factor of atomic size parameter has the largest effect on the Cmax of the V binary alloy; followed by the factor of electronegativity difference; the electrons concentration has the smallest effect among the three bond parameters. Function Zf is used for predicting the unknown Cmax of the transition metals in vanadium solvent. The results are compared with Darken-Gurry theorem, which can be deduced by the obtained function Zf in this work.     

Pressure–composition–temperature hysteresis in C14 Laves phase alloys: Part 3. Empirical formula

In Part 1 and Part 2 of this series of papers, the pressure–concentration–temperature (PCT) isotherms hysteresis was found to be closely related to the axial ratio a/c for both simple ternary and more complicated multi-element C14 Laves phase based alloys. Furthermore, the particle pulverization rate, which is the major determining factor in the duration of metal hydride electrode cycling, was found to correlate well with PCT hysteresis. In the current Part 3, we discuss an empirical equation which was developed to predict the PCT hysteresis of battery alloys through the study of the lattice constant ratios of a series of ZrCr₂-based ternary alloys. The empirical formula can then be used to estimate the pulverization rate of metal hydride electrode. To fit the empirical formula, an equivalent number of outer shell electrons for some non-transition metals was calculated from the axial ratio of ZrCr_1.8M_0.2 ternary alloys, where M is an element from the group of Al, Si, Ga, Ge, and Sn. Other factors, such as the amount of substitution, the difference in A and B element electronegativities, atomic size, and the choice of A element, were also investigated.     

Structural stability of Fe-based topologically close-packed phases

Precipitates of topologically close-packed (TCP) phases play an important role in hardening mechanisms of high-performance steels. We analyze the influence of atomic size, electron count, magnetism and external stress on TCP phase stability in Fe-based binary transition metal alloys. Our density-functional theory calculations of structural stability are complemented by an analysis with an empirical structure map for TCP phases. The structural stability and lattice parameters of the Fe–Nb/Mo/V compounds are in good agreement with experiment. The average magnetic moments follow the Slater-Pauling relation to the average number of valence-electrons and can be rationalized in terms of the electronic density of states. The stabilizing effect of the magnetic energy, estimated by additional non-magnetic calculations, increases as the magnetic moment increases with band filling for the binary systems of Fe and early transition metals. For the case of Fe₂Nb, we demonstrate that the influence of magnetism and external stress is sufficiently large to alter the energetic ordering of the closely competing Laves phases C14, C15 and C36. We find that the A15 phase is not stabilized by atomic-size differences, while the stability of C14 is increasing with increasing difference in atomic size.     

块体非晶合金的成分设计准则

综述了块体非晶合金的成分设计准则,如：约化玻璃转变温度、＂混乱＂准则、Inoue准则、Johnson准则、原子尺寸比例准则、γ参数准则、电子浓度准则及相选择准则。并简要讨论了目前存在的问题及发展趋势。     

Interpretation of viscous deformation of Zr-based bulk metallic glass alloys based on Nabarro-Herring creep model

Superplastic-like viscous deformation of bulk metallic glass alloys around the glass transition temperature (Tg) was analyzed based on the Nabarro-Herring creep model, a classical creep model, where the diffusional motion of atoms or vacancies through the lattice (atomic configuration) is considered. The amorphous matrix of bulk metallic glasses that has a randomly-packed atomic configuration was assumed to behave in a manner similar to the grain boundary in polycrystalline metals so as to approximate the diffusivity of the major constituent element. In spite of rough approximation of the parameters in the Nabarro-Herring creep equation, a reasonable value of the diffusion path (d) could be obtained from the experimentally-obtained metal flow data, including the steady state stress and the strain rate. Due to the absence of vacancy sources such as grain boundaries in homogeneous metallic glasses, the diffusion path, which, in polycrystalline materials, generally is the average distance between vacancy sources such as grain boundaries, was considered in this work as the average distance between tunneling centers in bulk metallic glass alloys. The calculated diffusion path was comparable to the density of tunneling centers around Tg, proposed by M. H. Cohen and G. S. Grest based on free volume theory. The calculated diffusion path showed monotonous decrease with temperature over Tg for Zr-based bulk metallic glass alloys. Based on this analysis, a schematic model for viscous deformation of bulk metallic glass was proposed.     

Catalytic Effect Analysis of Metallic Catalyst During Diamond Single Crystal Synthesis

By transition metals （Fe, Ni, Mn, Co） and their alloys as catalysts during the diamond synthesis, some transition phases will be formed, such as FeaC type carbides and y solid solutions. Based on the empirical electron theory of the solid and molecules, the valence electron structures of different kinds of carbides and y solid solutions and the relative electron density differences of various diamond/carbide and y solid solution/carbide interfaces were calculated and analyzed in this paper. The electron structure conditions of the ideal catalyst were presented by analyzing the different catalytic effects of the catalysts, which provide a new theoretical path to the optimal design of the catalyst composition     

LAVES PHASE ALLOYS FOR HIGH TEMPERATURE APPLICATIONS

１　ＩＮＴＲＯＤＣＴＩＯＮＴｈｅｌａｒｇｅｓｔｇｒｏｕｐｏｆｉｎｔｅｒｍｅｔａｌｌｉｃｓｉｓｆｏｒｍｅｄｂｙｔｈｅＬａｖｅｓｐｈａｓｅｓ,ｗｈｉｃｈｃｒｙｓｔａｌｌｉｓｅｗｉｔｈｔｈｅｈｅｘａｇｏｎａｌＣ１４ｓｔｒｕｃｔｕｒｅ,ｔｈｅｃｕｂｉｃＣ１５ｓｔｒｕｃｔｕｒｅｏｒｔｈｅｄｉｈｅｘａｇｏｎａｌＣ３６ｓｔｒｕｃｔｕｒｅ［１］．ＶａｒｉｏｕｓＬａｖｅｓｐｈａｓｅｓｈａｖｅａｔｔｒａｃｔｅｄｉｎｔｅｒｅｓｔａｌｒｅａｄｙｉｎｔｈｅｐａｓｔｆｏｒａｐｐｌｉｃａｔｉｏｎｓａｓｓｕｐｅｒｃｏｎｄｕ…     

Phase Stability of Low-Density,Multiprincipal Component Alloys Containing Aluminum,Magnesium, and Lithium

A series of low-density, multiprincipal component alloys containing high concentrations of Al, Mg, Li, Zn, Cu and/or Sn was designed using a strategy based on high-entropy alloys (HEAs). The alloys were prepared by induction melting under high-purity argon atmosphere, and the resulting microstructures were characterized in the as-cast condition. The resulting microstructures are multiphase and complex and contain significant volume fractions of disordered solutions and intermetallic compounds. By analyzing the atomic size difference, enthalpy of mixing, entropy of mixing, electronegativity difference, and valence electron concentration among the constituent elements, modified phase formation rules are developed for low-density multiprincipal component alloys that are more restrictive than previously established limits based on more frequently studied HEAs comprising mostly transition metals. It is concluded that disordered solid solution phases are generally less stable than competing ordered compounds when formulated from low-density elements including Al, Mg, and Li.     

Corrosion behavior of Fe-Cr and Fe-Ni-base commercial alloys in flowing Ar-42.6%O2-14.7%Br2 gas mixture at 700 °C

The corrosion behavior of Fe-Cr and Fe-Ni-Base commercial alloys has been investigated in an argon-42.6% oxygen-14.7% bromine gas mixture at 700 °C which was one of the environments encountered in the UT-3 thermochemical water decomposition reaction process to produce hydrogen. The test alloys were type 304 and 310 stainless steels, Incoloy 800, and Incoloy 825. Two-dimensional thermodynamic phase stability diagrams were constructed for iron, chromium, nickel, and titanium to predict the condensed corrosion products that are stable with respect to the representative alloying elements when the alloy is exposed to the argon-42.6% oxygen-14.7% bromine gas mixture at 700 °C. The oxides were thermodynamically stable phases with respect to the corresponding metals. Post-reaction treatment of test alloys included discontinuous mass-change measurements, scanning electron microscopy (SEM), electron probe micro-analysis (EPMA) for morphological and compositional investigation of the corrosion products, and the X-ray diffraction (XRD) for phase identification. XRD identified oxides and spinels as corrosion products but low-melting metal bromides were detected for all alloys with deleterious effects on high-temperature properties of these alloys during exposure to the environment. The poor corrosion resistance of the test alloys was mainly caused by the cracking and spalling of iron and chromium-rich oxides and further growth of various metal bromides beneath the oxide scale following prolonged exposure. The high iron content of the test alloys had deleterious effects on the performance of these alloys in the environment.     

应变速率、液体体积分数和液体粘度对金属半固态成形变形力的影响

建立了用于描述金属及颗粒增强金属基复合材料在半固态下一维等温轴对称压缩变形行为的理论模型。使用有限差分技术和铝合金的参数来进行模型计算。根据模型的计算结果 ,研究了应变速率、液体体积分数和液体粘度对金属在两平行板间半固态压缩变形力的影响。结果表明 ,液体粘度对变形力几乎没有影响 ,变形力随轴向应变速率绝对值的增加而增加 ,随液体体积分数的增加而明显减少。     

METASTABLE EXTENSION OF SOLID SOLUBILITY OF CERTAIN SIMPLE METALS OR METALLOIDS IN Ag

用点阵参数法研究了在熔体淬火条件下若干简单金属与类金属在Ag中固溶度的亚稳扩展。发现与Ag发生一系列包晶反应的二元合金的固溶度扩展符合电子浓度规律,并结合相图特征讨论了包晶系固溶度扩展的规律。简单共晶合金的固溶度扩展并不满足电子浓度规律,用Miedema理论解释了Si在Ag中固溶度低的原因。     

A first-principles investigation of the effect of relaxation on the alloy formation in the aluminum-3d-transition-metal system

The aim of this investigation is to establish the effect of relaxation on the formation of ordered substitutional solid solutions in Al_{1 ? x} M _x alloys (M = 3d metal; x = 1.6 at %). As the main parameters of the process of formation of the aluminum-based solution, thermodynamic quantities such as the energy of dissolution and the cohesive energy have been chosen; for choosing the most appropriate substitutional element, an analysis of the relaxation energy and deviations of empirical atomic radii of the impurity from the radius of the matrix-forming element has been suggested. It has been shown that there is a correlation between these thermodynamic quantities through the behavior of the density of electronic states and the Fermi energy. A regular relation has also been demonstrated to exist between the relaxation and stability of arising solid solutions, which supports the applicability of the analysis of relaxation energy depending on the atomic radius of the matrix-substituting element. The presence of anomalies in the behavior of magnetic properties of some aluminum alloys with transition metals has been shown and their explanation is given.     

Bulk amorphous metal—An emerging engineering material

During the last two decades, researchers have developed families of metal alloys that exhibit exceptional resistance to crystallization in the undercooled liquid state. Upon cooling, these alloys readily form glass or vitrify to form bulk amorphous alloys or bulk metallic glasses. The stability of the undercooled molten alloys with respect to crystallization has enabled studies of liquid thermodynamics, rheology, atomic diffusion, and the glass transition previously not possible in metallic systems. Bulk amorphous alloys exhibit very high strength, specific strength, and elastic strain limit, along with unusual combinations of other engineering properties. These factors, taken together, suggest that bulk amorphous metals will become widely used engineering materials during the next decade.     

9%Cr-1%Mo耐热钢焊缝金属连续冷却组织转变

利用Ｆｏｒｍａｓｔｏｒ－Ｄ全自动热膨胀记录仪测定了三种改进型９％Ｃｒ－１％Ｍｏ耐耐热钢焊缝金属的连续冷却组织转变相图,并用光学显微镜和透射是分析了各种冷却条件下的组织转变特点。结果表明,在很大的冷却范围内,三种焊缝金属的工体均只发生马氏体转变,只有当冷速足够慢时才发生先共析铁素体转变和共析转变。其中,含合金元素较少的２号焊缝金属具有最快的先共析铁素体形成冷速。研究发现,三种焊缝金属的奥氏体均形成板     

Empirical design of single phase high-entropy alloys with high hardness

We collect the available basic properties of nearly 100 high-entropy alloys (HEAs) with a single face centered cubic (fcc) or body centered cubic (bcc) phase. HEAs crystallizing in the fcc structure are mainly composed of the late 3d elements (LTM-HEAs), whereas HEAs consisting of the early (refractory) transition elements and the LTM-HEAs containing an increased level of bcc stabilizer form the bcc structure. Guided by the solid solution theory, we investigate the structure and hardness of HEAs as a function of the valence electron concentration (VEC) and the atomic size difference (δ). The fcc structure is found for VEC between 7.80 and 9.50, whereas the structure is bcc for VEC between 4.33 and 7.55. High strength is obtained for an average valence electron number VEC ∼ 6.80 and for an average atomic size difference δ ≈ 6%. Based on these empirical correlations, one can design the high-entropy alloys with desired hardness.     

The Internal Oxidation of Ternary Alloys. VI: The Transition from Internal to External Oxidation of the Most-Reactive Component under Intermediate Oxidant Pressures

The conditions for the transition from internal to external oxidation of the most-reactive component C of ternary A–B–C alloys are examined, assuming the presence of external scales of the oxide of the component of intermediate reactivity B. For this, approximate expressions for the diffusion coefficient of oxygen and for the concentration of oxygen dissolved in the binary A–B alloy matrix within the zone of internal oxidation as functions of the composition of the metal matrix within the zone of internal oxidation are used. Numerical calculations of the critical content of C needed for this transition are carried out for different combinations of values of the various parameters involved. The results obtained for the ternary alloys are compared with the corresponding data calculated for the binary A–C and B–C alloys under oxygen pressures insufficient to oxidize the most-noble alloy component. This allows to predict the possibility of existence of a third-element effect under intermediate oxidant pressures.     

On the correlation between electron structure and short range atomic order in iron-based alloys

The experimental data on the concentration of free electrons in fcc iron-based alloys, results of theoretical calculations on the electronic structure and experimental data of atomic distribution are analysed. The electron structure of iron-based substitutional solid solutions and CrNi austenitic steels alloyed by Mn, Mo, Cu, Si, Al and C, N was studied by means of the measurement of conduction electron spin resonance. The electron exchange in binary fcc Fe–N and Fe–C alloys was also calculated using an ab initio norm-conserving pseudopotential method. It is shown that Ni, Cu, Si and Al increase the concentration of free electrons, whereas Cr, Mn and Mo decrease it. Theoretical calculations as well as experimental data show that nitrogen in fcc iron and iron-based solid solutions increases the state density at the Fermi surface, whereas carbon contributes its electrons to the states below the Fermi surface. Mössbauer spectroscopy was used to study the distribution of carbon and nitrogen in binary fcc Fe–C and Fe–N alloys, while the data on the distribution of d-solutes in multicomponent solid solutions were obtained from the analysis of the contributions of different electronic subsystems, namely free electrons, isolated localized d-electrons (single solute d-atoms) and superparamagnetic clusters (clusters of d-atoms), to the temperature dependence of the magnetic susceptibility. The results of studies concerning the atomic distribution are consistent with the available data on the short range order in iron-based alloys. The following correlation is found: an increase in the concentration of free electrons assists the short range atomic ordering in iron-based alloys, whereas the localization of electrons promotes clustering of solute atoms. The state of atomic order influences properties like austenite stability, corrosion resistance and strength.     

Corrosion behavior of Ni-Cr-base commercial alloys in flowing Ar-42.6%O2-14.7%Br2 gas mixture at 700°C

Corrosion behavior of Ni-Cr-Base commercial alloys has been investigated in an argon-42.6% oxygen-14.7% bromine gas mixture at 700°C which was one of the environments encountered in the UT -3 thermochemical water decomposition reaction process to produce hydrogen. The test alloys were Inconel 600, Hastelloy C-276, Inconel 625, and Nimonic 80A. Two-dimensional thermodynamic phase stability diagrams were constructed for nickel, chromium, iron, tungsten, cobalt, titanium, and aluminium to predict the condensed corrosion products that are stable with respect to the representative alloying elements when the alloy is exposed to the argon-42.6% oxygen-14.7% bromine gas mixture at 700°C. The oxides were thermodynamically stable phases with respect to the corresponding metals. Post-reaction treatment of test alloys included discontinuous mass-change measurements, scanning electron microscopy (SEM), electron probe micro-analysis (EPMA) for morphological and compositional investigation of the corrosion products, and the X-ray diffraction (XRD) for phase identification. XRD identified oxides and spinels as corrosion products but low-melting metal bromides were also detected for all alloys with deleterious effects on high-temperature properties of these alloys during exposure to the environment. The poor corrosion resistance of Inconel 600 and Hastelloy C-276 was mainly caused by the cracking and spalling of iron and nickel-rich oxides and further growth of various metal bromides beneath the oxide scale following prolonged exposure. Inconel 625 and Nimonic 80A alloys performed better than Inconel 600 and Hastelloy C-276, mainly because of their aluminium alloying element and lower iron content.