A Future Life of Binary Phase Diagrams

The article raises the question of what to do with one of the main achievements of metal science in recent years—binary phase diagrams. These diagrams play a key role in the science of alloys and therefore their reliability must be complete. However, the discovery of the “ordering-separation” phase transition, which showed that in binary alloys at certain temperatures the sign of the chemical interatomic interaction changes (and, consequently, the microstructure changes), forces us to reconsider our ideas about those areas. Currently, these areas are designated on diagrams as areas of a “disordered solid solution.” This article proposes, using transmission electron microscopy, to study all the so-called solid solution regions, and apply the results obtained to the studied regions of the phase diagram.

Holographic alloy positioning design system and holographic network phase diagrams of Au-Cu system

Taking Au?Cu system as an example, three discoveries and two methods were presented. First, a new way for boosting sustainable progress of systematic metal materials science (SMMS) and alloy gene engineering (AGE) is to establish holographic alloy positioning design (HAPD) system, of which the base consists of measurement and calculation center, SMMS center, AGE center, HAPD information center and HAPD cybernation center; Second, the resonance activating-sychro alternating mechanism of atom movement may be divided into the located and oriented diffuse modes; Third, the equilibrium and subequilibrium holographic network phase diagrams are blueprints and operable platform for researchers to discover, design, manufacture and deploy advanced alloys, which are obtained respectively by the equilibrium lever numerical method and cross point numerical method of isothermal Gibbs energy curves. As clicking each network point, the holographic information of three structure levels for the designed alloy may be readily obtained: the phase constitution and fraction, phase arranging structure and properties of organization; the composition, alloy gene arranging structure and properties of each phase and the electronic structures and properties of alloy genes. It will create a new era for network designing advanced alloys.

Alloy gene Gibbs energy partition function and equilibrium holographic network phase diagrams of Au_3Cu-type sublattice system

Taking Au3Cu-type sublattice system as an example, three discoveries have been presented. First, the fourth barrier to hinder the progress of metal materials science is that today’s researchers do not understand that the Gibbs energy function of an alloy phase should be derived from Gibbs energy partition function constructed of alloy gene sequence and their Gibbs energy sequence. Second, the six rules for establishing alloy gene Gibbs energy partition function have been discovered, and it has been specially proved that the probabilities of structure units occupied at the Gibbs energy levels in the degeneracy factor for calculating configuration entropy should be degenerated as ones of component atoms occupied at the lattice points. Third, the main characteristics unexpected by today’s researchers are as follows. There exists a single-phase boundary curve without two-phase region coexisting by the ordered and disordered phases. The composition and temperature of the top point on the phase-boundary curve are far away from those of the critical point of the Au3Cu compound; At 0 K, the composition of the lowest point on the composition-dependent Gibbs energy curve is notably deviated from that of the Au3Cu compounds. The theoretical limit composition range of long range ordered Au3Cu-type alloys is determined by the first jumping order degree.

Alloy gene Gibbs energy partition function and equilibrium holographic network phase diagrams of AuCu_3-type sublattice system

Taking AuCu3-type sublattice system as an example, three discoveries have been presented: First, the third barrier hindering the progress in metal materials science is that researchers have got used to recognizing experimental phenomena of alloy phase transitions during extremely slow variation in temperature by equilibrium thinking mode and then taking erroneous knowledge of experimental phenomena as selected information for establishing Gibbs energy function and so-called equilibrium phase diagram. Second, the equilibrium holographic network phase diagrams of AuCu3-type sublattice system may be used to describe systematic correlativity of the composition?temperature-dependent alloy gene arranging structures and complete thermodynamic properties, and to be a standard for studying experimental subequilibrium order-disorder transition. Third, the equilibrium transition of each alloy is a homogeneous single-phase rather than a heterogeneous two-phase, and there exists a single-phase boundary curve without two-phase region of the ordered and disordered phases; the composition and temperature of the top point on the phase-boundary curve are far away from the ones of the critical point of the AuCu3 compound.

Solubility and phase diagrams of hydroxyl manganese chloride

In the course of the basic research on the ammonia-evaporation reaction of manganese monoxide （MnO）, hydroxyl manganese chloride （Mn2（OH）3Cl） was found. The solubility and phase diagrams of the hydroxyl manganese chloride were investigated. The aqueous thermostat and vibrating bed were used to determine the solubility of hydroxyl manganese chloride in water, ammonium chloride and manganese chloride system, and the phase diagrams of multicomponent system were drawn. The research results indicate that hydroxyl manganese chloride has been produced in laboratory and is in favor of the solid-liquid separation at high temperature.

Towards high strength cast Mg-RE based alloys:Phase diagrams and strengthening mechanisms

Mg-rare earth(RE)based systems provide several important commercial alloys and many alloy development opportunities for high strength applications,especially in aerospace and defense industries.The phase diagrams,microstructure,and strengthening mechanisms of these multicomponent systems are very complex and often not well understood in literature.We have calculated phase diagrams of important binary,ternary,and multicomponent RE-containing alloy systems,using CALPHAD(CALculation of PHAse Diagrams).Based on these phase diagrams,this paper offers a critical overview on phase equilibria and strengthening mechanisms in these alloy systems,including precipitation,long period stacking order(LPSO),and other intermetallic phases.This review also summarized several promising Mg-RE based cast alloys in comparison with commercial WE54 and WE43 alloys;and explored new strategies for future alloy development for high strength applications.It is pointed out that the combination of precipitation and LPSO phases can lead to superior strength and ductility in Mg-RE based cast alloys.The precipitates and LPSO phases can form a complex three-dimensional network that effectively impedes dislocation motion on the basal and non-basal planes.The LPSO phases can also prevent the coarsening of precipitates when they interact,thus providing good thermal stability at elevated temperatures.Future research is needed to determine how the combination of these two types of phases can be used in alloy design and industrial scale applications.

Thermodynamic Modeling and Phase Diagrams of Hexagonal and Cubic GaN Single-Crystal FilmGrowth by ECR-PEMOCVD Method

Based on thermodynamic equilibrium theory,a chemical equilibrium model for GaN g rowth is given in electron cyclotron resonance plasma enhanced metalorganic chem ical vapor deposition (ECR-PEMOCVD) system.Calculation indicates that the growt h driving force are functions of growth conditions:group Ⅲ input partial press ure,input Ⅴ/Ⅲ ratio,and growth temperature.Furthermore,the growth phase diag rams of hexagonal and cubic GaN film growth are obtained,which are consistent wi th our experimental conditions to some extent.Through analysis,it is explained t he reason that high temperature and high input Ⅴ/Ⅲ ratio are favorable for he xagonal GaN film growth.This model can be extended to the similar systems used f or GaN single-crystal film growth.

Optimization and Calculation of TbCl_3-ACl (A=Li, Na, K, Rb, Cs) Phase Diagrams

By using CALPHAD (Calculation of Phase Diagram) technique the optimization and calculation of the binary systems of TbCl_3-ACl (A= Li, Na, K, Rb, Cs) were carried out. For describing the Gibbs free energy of liquid phase in these systems the new modified quasichemical model in the pair-approximation for short-range ordering was used. From measured phase equilibria data and experimental integral properties the TbCl_3-ACl phase diagrams were optimized and calculated. A set of thermodynamic functions was optimized based on an interactive computer-assisted analysis. The calculated phase diagrams and thermodynamic data are self-consistent.

Determination of High Pressure Phase Diagrams of the Ternary Alloy System

everal vertical sections of the phase diagram of Cd-Sn-Zn system with a constant mole fraction X_(cd)=0.2 were determined by means of differential thermal anal- ysis(DTA)at high pres:ures 0.0,0.5,1.5,and 2. 0 GPa respectively. The eutectic temperature of the system increases by about 50K from atmospheric pressure to the high pressure 2.0 GPa,but the ternary eutectic composition changes slightly with the pressure chnge.

Phase diagrams in mixed spin-3/2 and spin-2 Ising system with two alternative layers within the effective-field theory

The phase diagrams in the mixed spin-3/2 and spin-2 Ising system with two alternative layers on a honeycomb lattice are investigated and discussed by the use of the effective-field theory with correlations. The interaction of the nearest-neighbour spins of each layer is taken to be positive （ferromagnetic interaction） and the interaction of the adjacent spins of the nearest-neighbour layers is considered to be either positive or negative （ferromagnetic or antiferromagnetic interaction）. The temperature dependence of the layer magnetizations of the system is examined to characterize the nature （continuous or discontinuous） of the phase transitions and obtain the phase transition temperatures. The system exhibits both second- and first-order phase transitions besides triple point （TP）, critical end point （E）, multicritical point （A）, isolated critical point （C） and reentrant behaviour depending on the interaction parameters. We have also studied the temperature dependence of the total magnetization to find the compensation points, as well as to determine the type of behaviour, and N-type behaviour in Neel classification nomenclature existing in the system. The phase diagrams are constructed in eight different planes and it is found that the system also presents the compensation phenomena depending on the sign of the bilinear exchange interactions.

Magnetization and magnetic phase diagrams of a spin-1/2 ferrimagnetic diamond chain at low temperature

We used the Jordan-Wigner transform and the invariant eigenoperator method to study the magnetic phase diagram and the magnetization curve of the spin-1/2 alternating ferrimagnetic diamond chain in an external magnetic field at finite temperature.The magnetization versus external magnetic field curve exhibits a 1/3 magnetization plateau at absolute zero and finite temperatures,and the width of the 1/3 magnetization plateau was modulated by tuning the temperature and the exchange interactions.Three critical magnetic field intensities H_(CB),H_(CE)and H_(CS) were obtained,in which the H_(CB) and H_(CE)correspond to the appearance and disappearance of the 1/3 magnetization plateau,respectively,and the higher H_(CS) correspond to the appearance of fully polarized magnetization plateau of the system.The energies of elementary excitation hω_(σ,k)(σ=1,2,3)present the extrema of zero at the three critical magnetic fields at 0 K,i.e.,[hω_(3,k)(H_(CB)]_(min)=0,[hω_(2,k)(H_(CE)]_(max)=0 and[hω_(2,k)(H_(CS)]_(min)=0,and the magnetic phase diagram of magnetic field versus different exchange interactions at 0 K was established by the above relationships.According to the relationships between the system’s magnetization curve at finite temperatures and the critical magnetic field intensities,the magnetic field-temperature phase diagram was drawn.It was observed that if the magnetic phase diagram shows a three-phase critical point,which is intersected by the ferrimagnetic phase,the ferrimagnetic plateau phase,and the Luttinger liquid phase,the disappearance of the 1/3 magnetization plateau would inevitably occur.However,the 1/3 magnetization plateau would not disappear without the three-phase critical point.The appearance of the 1/3 magnetization plateau in the low temperature region is the macroscopic manifestations of quantum effect.

Development of advanced materials based on phase diagrams and microstructural control

Recent progress on research activities of phase diagrams in our laboratory has been presented. Experimental studies and thermodynamic calculations based on CALPHAD (Calculation of Phase Diagrams) method have been conducted in the following alloy systems.1.Database on microalloying steels including carbide, nitride and sulfide is now being constructed.2.ADAMIS (Alloy Database for Micro-Solders) containing 8 elements of Ag, Bi, Cu,In, Sb, Sn, Zn and Pb has been constructed, which can handle all combinations of these elements and all composition ranges.3.A thermodynamic database of Cu-base alloys including Cu-X binary system and Cu-Fe, Cu-Ni, Cu-Cr base ternary systems has been constructed.4.Experimental and thermodynamic calculations on Fe, Ni, Co and Ti aluminides have been conducted.5.Experimental and thermodynamic calculations on Co base magnetic recording media have been conducted.6.Thermodynamic analysis of interaction between magnetic and chemical orderings has been performed.By utilizing the information on phase diagrams, the following advanced materials have been developed. (A)New type of high speed steel with high hardness about Hv≈1000 by carbide dispersion carburizing method. (B)New Pb-free machinable stainless steel using titanium carbosulphide. (C)New Pb-free solder for Die-attaching use. (D)Shape memory alloys; Cu-base, Ferromagnetic Ni-base and Fe-base. (E)Invar alloys. (F)Egg-type powder.Typical examples of phase diagrams, phase stability, database and its application for the development of advanced materials will be presented.

ASSESSMENT AND OPTIMIZATION OF THE PHASE DIAGRAMS AND THERMODYNAMIC DATA OF SOME BINARY SYSTEMS CONTAINING PRASEODYMIUM CHLORIDES

In this paper a critical assessment and optimization of the phase diagrams and thermodynamic properties of the PrCl_3-MCl(M=Li,Na)and PrCl_3-MCl_2(M=Mg,Ca,Sr,Ba) binary systems have been per- formed.The assessed and optimized binary phase diagrams and thermodynamic data with self consistency are a better basis for constructing multicomponent phase diagrams.

MY RESEARCH ACHIEVEMENTS IN POWDER X-RAY DIFFRACTION & PHASE DIAGRAMS

I graduated from the Department of Chemistry, Xiamen University in 1955, majoring in physical chemistry. I went to the Institute of Metallurgy under the Soviet Academy of Sciences in 1956 as a Ph.D.candidate in thermochemistry and crystal chemistry of metal alloys,and got my Ph.D.degree in 1960.In the following 30 years, I did basic and applied research in interdisciplines,including crystal chemistry,materials science and solid state physics.My main achievements can be listed in two aspects as follows:

New formulae for calculating activities from binary system phase diagrams containing solid solution by introducing the parameterθ

New formulae for calculating activities and activity coefficients from binary phase diagrams containing solidsolution are presented. In the new formulae, a parameterθ is introduced. It seems be more efficient The application ofthese formulae to system Ag-Pb proves its efficiency.

NEW METHODS FOR CALCULATING ACTIVITIES OF COMPONENTS FROM PHASE DIAGRAMS IN BINARY PERITECTIC SYSTEMS

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Thermodynamic database of the phase diagrams in the Mg-Al-Zn-Y-Ce system

The Mg-Al-Zn-Y-Ce system is one of the key systems for designing high-strength Mg alloys. The purpose of the present article is to develop a thermodynamic database for the Mg-Al-Zn-Y-Ce multicomponent system to design Mg alloys using the calculation of phase diagrams （CALPHAD） method, where the Gibbs energies of solution phases such as liquid, fcc, bcc, and hcp phases were described by the subregular solution model, whereas those of all the compounds were described by the sublattice model. The thermodynamic parameters describing Gibbs energies of the different phases in this database were evaluated by fitting the experimental data for phase equilibria and thermodynamic properties. On the basis of this database, a lot of information concerning stable and metastable phase equilibria of isothermal and vertical sections, molar fractions of constituent phases, the liquidus projection, etc., can be predicted. This database is expected to play an important role in the design of Mg alloys.

The Collins Model and the Eutectic—Type and the Peritectic—Type Phase Diagrams

From the Gibbs free energy and the equations of two-phase equilibrium curves of the two-dimensionalbinary system which has the Lennard-Jones potential, using the Collins model, the eutectic-type phase diagram and theperitectic-type phase diagram of the binary system are obtained, whose results are quite similar to the behavior of thethree-dimensional (3D) substances.

PHASE DIAGRAMS AND σ- PHASE PRECIPITATION IN SOME STAINLESS STEELS

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Calculation of RECl_3-CaCl_2-LiCl Phase Diagrams(RE=La, Ce, Pr, Nd)

Based on the assessment and optimization of nine experimental sub-binary phase diagramsand thermodynamic data (RECl3-LiCl, RECl3-CaCl2 and CaCl2-LiCl), four phase diagrams of theRECl3-CaCl2-LiCl systems are calculated and brieflly discussed.