Formation Of Ternary Intermetallic Compounds Research Articles

Thermodynamic Optimisation of the Ni-Al-Y Ternary System

Ni-base superalloys become more attractive recently for its use in aerospace. As one of the most important constitutional ternary system the Ni-Al-Y system has been thermodynamically optimised in the present work. Solubility of yttrium in fcc-nickel and fcc-aluminium has been taken into account since yttrium can be used as an alloy element in Ni-base superalloys. A comprehensive set of thermodynamic parameters have been obtained. Calculated phase equilibria and enthalpies of formation of ternary intermetallic compounds are consistent with experimental data. This work can be used as basis of multi-component thermodynamic database for Ni-base alloys.

The strength of chemical bonds in solids and liquids

The strengths of chemical bonds between atoms are accurately measured and widely available for molecular gases, but an established method of quantifying bond strengths in liquids and solids is not available, and the strengths of these bonds are generally unknown. A new term, the condensed bond enthalpy (CBE), is proposed to specify the energy contained in bonds between atoms in condensed states. An approach to estimating these bond strengths is developed by combining classical thermodynamic concepts with measured heats of formation and crystallographic data. A nearly complete set of elemental CBE and a selection of CBE between unlike metal atom pairs are produced using the method described here. Elemental bond enthalpies generally range from about −0.1eV to −1.3eV, and bonds between unlike atoms studied here range from about −0.6eV to −1.1eV. The validity and utility of these values are demonstrated by using them to estimate enthalpies of fusion and surface energies in elemental metals and heats of formation of ternary intermetallic compounds. Predicted enthalpies are generally within experimental errors for all three comparisons. Bond enthalpies are found to have a mild but systematic dependence on chemistry and atomic structure in some of the binary systems studied here, but are essentially independent of the atomic environment in other systems. The uncertainty in εij values (±4%) is small enough to enable classical approximations, but is inadequate when higher precision is needed.

DMiner-I: A software tool of data mining and its applications

SummaryA software tool for data mining (DMiner-I) is introduced, which integrates pattern recognition (PCA, Fisher, clustering, HyperEnvelop, regression), artificial intelligence (knowledge representation, decision trees), statistical learning (rough set, support vector machine), and computational intelligence (neural network, genetic algorithm, fuzzy systems). It consists of nine function models: pattern recognition, decision trees, association rule, fuzzy rule, neural network, genetic algorithm, HyperEnvelop, support vector machine and visualization. The principle, algorithms and knowledge representation of some function models of data mining are described. Nonmonotony in data mining is dealt with by concept hierarchy and layered mining. The software tool of data mining is realized byVisual C++under Windows 2000. The software tool of data mining has been satisfactorily applied in the prediction of regularities of the formation of ternary intermetallic compounds in alloy systems, and diagnosis of brain glioma.

TICP — an expert system applied to predict the formation of ternary intermetallic compounds

A four-parameter model based on extended Miedema's cellular model of alloy phases and pattern recognition methods has been used to study the regularities in the formation of ternary intermetallic compounds. According to some empirical criterions that have been found, we build an expert system to predict whether a ternary alloy system forms the ternary intermetallic compound or not.

Regularities of formation of ternary intermetallic compounds between two transition elements and one non-transition element

The pattern recognition methods and a four-parameter model, based on extended Miedema’s cellular model of alloy phases, are used to study the regularities of formation of ternary compounds between two transition elements (T, T′) and one non-transition element (N) (T-T′-N system). The criterion of formation can be expressed as some functions of ϕ (electronegativity),nws1/3 (valence electron density in Wagner-Seitz cell),R (Pauling’s metallic radii) andZ (number of valence electrons in atom).

Regularities of formation of ternary alloy phases between non-transition metals

Using a four-parameter model based on extended Miedema’s cellular model of alloy phases and pattern recognition methods, the regularities of formation of ternary intermetallic compounds between non-transition metals have been investigated. The criterion of formation can be expressed as some empirical functions of ϕ (electronegativity),n WS 1/3 (valence electron density in Wagner-Seitz cell),R (Pauling’s metallic radius) andZ (number of valence electrons in atom).

Regularities of formation of ternary intermetallic compounds Part 4. Ternary intermetallic compounds between two nontransition elements and one transition element

Abstract Regularities in the formation of ternary intermetallic compounds consisting of one kind of transition element (T) and two kinds of nontransition elements (M, M′) have been studied by atomic parameter-pattern recognition methods. Some empirical criterions found are explained by the concepts of spd hybridization and charge transfer between the atoms of the constituent elements.

Regularities of formation of ternary intermetallic compounds

Villars’s system of atomic parameters, R sp , VE and X MB , has been used to investigate the regularities of the formation of ternary intermetallic compounds between one nontransition element (M) and two transition elements (T and T′). It has been found that ternary compounds are usually formed when T is an early transition metal and T′ is a late transition metal if X MB of the nontransition metal M is larger than 1.45. The regularities of formation of ternary intermetallic compounds in the T–T′–M with two late transition elements or two early transition elements are also investigated.

Regularities of formation of ternary intermetallic compounds

Regularities of the ternary intermetallic compound formation between three transition elements are studied by the pattern recognition–atomic parameter method. The influences of VE, R sp and X MB on the formation of the ternary intermetallic compounds are investigated. The criteria of ternary compound formation in the late transition element-containing systems, early transition element-containing systems, systems containing both the early transition element and late transition element, and the systems containing Mn-group elements are found by pattern recognition methods.

Regularities of formation of ternary intermetallic compounds

The regularities of ternary intermetallic compound formation between nontransition metallic elements have been studied by the atomic parameter-pattern recognition method using Villars’s system of atomic parameters ( R sp , VE, and X MB ). It has been found that the representative points of ternary compound forming alloy systems and that of ternary alloy systems without a ternary compound are distributed in different regions in the multi-dimensional space spanned by the atomic parameters or their functions. A hyperpolyhedron model obtained by pattern-recognition methods can be used to describe the boundaries of the zone of ternary compound formation in multi-dimensional space, with good computerized prediction for ternary intermetallic compound formation.

Investigation of the structure of ternary phases in AlMgTi, AlMgV and AlMgCr systems

The interaction of AlMg alloys containing 6–8 at.% magnesium with titanium, vanadium and chromium on the interface surface of diffusion couples at 800–820 K results in the formation of ternary intermetallic compounds and binary V 5Al 8 and Cr 4Al 9 compounds respectively. It was established for the first time using X-ray powder analysis, that ternary intermetallic compounds in the AlMgTi system crystallize with cubic symmetry with a = 14.77 ± 0.01 A ̊ . It was confirmed that ternary compounds in the AlMgV and AlMgCr systems have a cubic lattice with unit cell parameters a = 14.61 ± 0.01 A ̊ and a = 14.53 ± 0.01 A ̊ respectively (space group Fd3 m, 184 atoms in the unit cell).