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.

MOLTEN SALT PHASE DIAGRAMS CALCULATION USING ARTIFICIAL NEURAL NETWORK OR PATTERN RECOGNITION-BOND PARAMETERS PART 3.ESTIMATION OF LIQUIDUS TEMPERATURE AND EXPERT SYSTEM

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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.

PHASE DIAGRAMS AND σ- PHASE PRECIPITATION IN SOME STAINLESS STEELS

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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.

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.

θ Correction to the Analytical Expressions for Calculating Activities from Phase Diagrams Involving Intermediate Compounds

A set of correct expressions for calculating activities and activity coefficients from binary phase diagrams involving intermediate compounds are presented in this paper by the introduction of a correct parameter θ. The application of these expressions to system Mg-Sn shows that they are quite feasible.

Thermodynamic Optimization of TmCl_3-ACl (A=Na, K, Rb, Cs) Phase Diagrams

From the measured phase equilibria data and experimental thermochemical properties, the TmCl_3-ACl (A=Na, K, Rb, Cs) phase diagrams were optimized and calculated using the CALPHAD technique. For describing the Gibbs energies of the liquid phase in these systems, the new modified quasichemical model in the pair-approximation for short-range ordering was used. A set of thermodynamic functions was optimized and gotten based on an interactive computer-assisted analysis. The calculated phase diagrams and thermodynamic data are self-consistent.

Thermodynamic optimization and calculation of phase diagrams of YbCl_3-MCl (M=Na, K, Rb, Cs)

YbCl3-MCl （M = Na, K, Rb, Cs） systems were optimized and calculated using the CALPHAD （CALculation of PHAse Diagram） technique. The modified quasi-chemical model in the pair-approximation for short-range ordering was used to describe the Gibbs energies of liquid phase in the systems. On the basis of the measured phase diagram data and experimental thermodynamic properties, a series of thermodynamic functions were optimized and calculated through an interactive computer-assisted analysis. Furthermore, some reasonable discussions on the thermodynamic parameters for these strong interaction binary systems were carded out. The results showed that the optimized parameters and experimental data are thermodynamically self-consistent.

MOLTEN SALT PHASE DIAGRAMS CALCULATION USING ARTIFICIAL NEURAL NETWORK OR PATTERN RECOGNITION-BOND PARAMETERS Part 2.Prediction of phase diagrams of ternary molten salt systems

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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.

In situ observation of the phase transformation kinetics of bismuth during shock release

A time-resolved x-ray diffraction technique is employed to monitor the structural transformation of laser-shocked bismuth.Results reveal a retarded transformation from the shock-induced Bi-Ⅴphase to a metastable Bi-Ⅳphase during the shock release,instead of the thermodynamically stable Bi-Ⅲphase.The emergence of the metastable Bi-Ⅳphase is understood by the competitive interplay between two transformation pathways towards the Bi-Ⅳand Bi-Ⅲ,respectively.The former is more rapid than the latter because the Bi-Ⅴto B-Ⅳtransformation is driven by interaction between the closest atoms while the Bi-Ⅴto B-Ⅲtransformation requires interaction between the second-closest atoms.The nucleation time for the Bi-Ⅴto Bi-Ⅳtransformation is determined to be 5.1±0.9 ns according to a classical nucleation model.This observation demonstrates the importance of the formation of the transient metastable phases,which can change the phase transformation pathway in a dynamic process.

Phase-engineering modulation of Mn-based oxide cathode for constructing super-stable sodium storage

The Mn-based oxide cathode with enriched crystal phase structure and component diversity can provide the excellent chemistry structure for Na-ion batteries.Nevertheless,the broad application prospect is obstructed by the sluggish Na^(+)kinetics and the phase transitions upon cycling.Herein,we establish the thermodynamically stable phase diagram of various Mn-based oxide composites precisely controlled by sodium content tailoring strategy coupling with co-doping and solid-state reaction.The chemical environment of the P2/P'3 and P2/P3 biphasic composites indicate that the charge compensation mechanism stems from the cooperative contribution of anions and cations.Benefiting from the no phase transition to scavenge the structure strain,P2/P'3 electrode can deliver long cycling stability(capacity retention of 73.8%after 1000 cycles at 10 C)and outstanding rate properties(the discharge capacity of 84.08 mA h g^(-1)at 20 C)than P2/P3 electrode.Furthermore,the DFT calculation demonstrates that the introducing novel P'3 phase can significantly regulate the Na^(+)reaction dynamics and modify the local electron configuration of Mn.The effective phase engineering can provide a reference for designing other high-performance electrode materials for Na-ion batteries.

Ternary phase diagrams and solvate transformation thermodynamics of omeprazole sodium in different solvent mixtures

Omeprazole sodium(OMS), a typical non-hydrogen bond donors API, is only available in solvates so far, including monohydrate, ethanol solvate and methanol solvate. The methanol solvate was found for the first time. Solvate transformation thermodynamics of OMS was studied in this paper. First, the ternary phase diagrams forming two solvates for OMS in binary solvent mixtures including methanol + water, ethanol + water, and methanol+ ethanol were measured at temperature ranging of T =(278.15 to 313.15) K under atmospheric pressure. Further, the standard equilibrium constants of the solvate transformation reactions were evaluated according to the chemical reaction isothermal equation. The standard molar Gibbs free energy, the standard molar enthalpy, and the standard molar entropy of solvate transformation reactions were then calculated based on van't Hoff equation. Moreover, the thermodynamic stability of the OMS solvate was analyzed based on phase diagram. The results are of great importance to develop a crystallization process for manufacturing OMS solvate, and could be helpful to other solvate transformation research.

Relationship between the types of binary alloy phase diagrams of Ⅷ and IB group elements and the Mendeleev numbers

The relationship between the types of binary alloy phase diagramsof VIII and Ib group elements and the Men- deleev numbers wasdiscussed for the first time using the VIII and IB group elements assolvent metals (A) and the other elements as solute metals (B),basesd on their alloy phase diagram types. The Mendeleev numbers ofthe solvent metals and the solute metals were expressed as M_A andM_B, respectively. A two-dimension map of M_A/M_B was drawn. It isindi- cated that there is an oblique line in the map, which dividesthe binary alloy phase diagram types of solvent metals into twosymmetry parts, the phase diagram types of the other elements withsolvent metals located at the above or down of the line respectively,while on the line, △M = 0.

RECl_3-CaCl_2-MgCl_2 TERNARY PHASE DIAGRAMS(RE:La,Ce,Pr,Nd)

Nine sub-binary phase diagrams of the RECl3-CaCl2,RECl3-MgCl2 and CaCl2-MgCl2 systems,andthermodynamic data for these systems are critically assessed and optimized.Using Hillert model and takingMgCl2 as an asymmetric component,the ternary phase diagrams or the RECl3-CaCl2-MgCl2 systems are predtcted.As well,the determination of asymmetric component in the asymmetric model is investigated.

Phase diagrams and magnetic properties of the mixed spin-1 and spin-3/2 Ising ferromagnetic thin film: Monte Carlo treatment

Phase diagrams and magnetic properties of the mixed spin-1 and spin-3/2 Ising film with different single-ion anisotropies are investigated, by the use of Monte Carlo simulation based on heat bath algorithms. The effects of the crystal-fields and the surface coupling on the phase diagrams are investigated in detail and the obtained phase diagrams are presented. Depending on the Hamiltonian parameters, the system exhibits both second-and first-order phase transitions besides tricritical point, triple point, and isolated critical end point.

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.