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 propertiesof 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 area better basis for constructing multicomponent phase diagrams.     

Co-Cr系相平衡的热力学计算和fcc相的磁性诱导相分离

Two-phase equilibria between the ferromagnetic fcc and the paramagnetic fcc phase from 800 ℃ to 900 ℃ in the Co-rich region have been detected by the diffusion couple technique. Two phase separation region of the fcc has been confirmed along the Curie temperature. The phase equilibria including the present results and the thermodynamic data of the Co-Cr system reported in the literature were analyzed on the basis of the thermodynamic evaluation. A set of thermodynarnic values for the liquid, fcc, hcp, bcc, sigma phases was obtained. The calculated phase equilibria were in good agreement with most of the experimental data.     

Experimental Study and Thermodynamic Optimization of the FeO-V203 System

Optimization of the phase diagram of FeO-V20a system is a part of an on-going research project to develop a self-consistent multi-component thermodynamic database for vanadium slag from hot metal. Due to the lack o{ ex- perimental data for optimization, a novel experimental investigation has been carried out by thermal analysis （DSC） with a series of slags on different V2 03 contents （i. e. 3mass%- 12mass%）. All available thermodynamic and phase diagram data for the binary systems have been simultaneously optimized with CALPHAD （Calculation of Phase Dia- grams） methods to give one set of model equations for the Gibbs free energy of the liquid slag as functions of compo- sition and temperature. The modified quasi-chemical model was used to describe the binary slag system. It was dem- onstrated that the calculated phase diagram with the optimized parameters was in good agreement with the experi- mental data.     

Fabrication of Different SiC Architecture Via a Simple Method

Silicon carbide architecture with different morphology has been synthesized via catalyst-free carbothermic reduction of silica under normal atmosphere pressure.X-ray powder diffraction(XRD)and Scanning electron microscopy(SEM)were used to characterize the architecture.The results show that the mole ratio of carbon/silica has a great influence on the morphology of silicon carbide architecture.At different carbon/silica mole ratio,platelet-,bamboo-,pagoda-,and bead-like silicon carbide architecture have been synthesized.     

Ti-Mo-Sn形状记忆合金管在微导尿管上的应用

Recently, minimally invasive surgeries using guide-wire, catheter, stent etc. have spread rapidly as the diagnosis and the medical treatment for a cancer, a disease in a circulatory organ etc. Currently, further maneuverability and functionability of those devices are strongly desired in order to be used widely and safely. Although Ti-Ni shape memory alloys have been used in medical devices such orthodontic wire, guide-wire, it has been suspected that Ni is allergenic and carcinogenic to the human body. Thus the development of Ni-free shape memory alloys has been strongly required. Re- cently, several Ni-free beta-titanium alloys such as Ti-Mo-Al, Ti-Mo-Ga, Ti-Nb-Al have been developed as new-type shape memory alloys. We have been studying Ti-Mo based beta-titanium alloys and Ti-Mo-Sn alloy has constantly superelasticity of 3%. The purpose of present study is to propose the micro catheter with thin wall and high flexibility using To-Mo-Sn alloys tube on the basis of its mechanical properties.     

Prediction of Heat of Fusion of Rare Earth Compounds from Binary Phase Diagrams

Based on the thermodynamical principle the new formula for calculation of heat of fusion and its error havebeen derived from binary phase diagrams which could be classified to eutectic,solid solution,degenerate eutecticand involving a compound phase diagram and so on.Using these formulae heats of fusion of some rare earth ox-ides have been predicted.     

Key technologies of roll forming automobile components with AHSS

Lightweight design is one of the development trends of the automobile industry.An effective way to achieve lightweight auto bodies is to use AHSS (advanced high strength steel) for the safety components of automobiles.This study has taken doorsill reinforcements made of martensite AHSS as the object,and performed research on the AHSS roll forming technologies and prototype development of typical asymmetric open components.By means of finite element analysis (FEA) and simulation,studies have been carried out on the springback and edge wave defects during AHSS roll forming,and an optimized process design has been achieved.The generation mechanisms of vertical bows,horizontal cambers,twists,pre-punched hole distortion and cut end flare have been analyzed,and solutions to these defects have been given.In addition,tesing of the roll forming process for AHSS has been conducted and typical samples with required dimensional accuracy have been manufactured.This study has provided technical support for the large-scale application of AHSS.     

The Thermodynamics of Cu-La,Cu-Ce Systems

The Cu-La,Cu-Ce systems have been optimized using the recommended phase diagrams and the experi-mental thermodynamic values reported in the recent years.The optimization results are in good agreement withthe experimental data.     

电子组装无铅焊料的热力学、动力学计算及合金设计

Computational thermodynamics and kinetics were used to design the Pb-free micro-solders for replacing the conventional Sn-Pb solders because of the health and environmental safety problem.On the basis of CALPHAD (Calculation of Phase Diagrams) method we can easily calculate properties such as the liquidus projection, isothermal and vertical sectional diagrams and phase fraction in multicomponent system including Ag, Bi, Cu, In, Sb, Sn, Zn and Pb elements. In addition, other related information such as the surface tension, viscosity of the liquid phase and solidification simulation can also be obtained. DICTRA (Diffusion Controlled Transformation) software was used to simulate the interfacial reactions between substrate and Pb-free solders, which can easily give the information on the growth of intermetallic compounds and moving speed of interface between substrate and solders etc.     

LUMINESCENCE CENTERS OF Eu~(2 ) IN KCaF_3:Eu~(2 )

The nature of the emission center of Eu~(2 ) in KCaF_3:Eu~(2 ) strongly depends on the preparative condi-tions.Experimental results show that there are two different d→f transition emission bands,and the origin ofthese two emission bands,their interrelationship and the effect of doping concentration on them have been dis-cussed.A Eu~(2 )-Eu~(3 ) valency change process has been proposed.     

Simulation of paraequilibrium growth in multicomponent systems

A methodology to simulate paraequilibrium (PE) growth in multicomponent systems using the DIC-TRA (Diffusion-Controlled Transformation) software is presented. For any given multicomponent system containing substitutional and interstitial elements, the basic approach is to define a hypothetical element Z, whose thermodynamic and mobility parameters are expressed in terms of the weighted average (with respect to site fraction) of the thermodynamic parameters and mobilities of the substitutional alloying elements. This procedure facilitates the calculation of PE phase diagrams and the PE growth simulations directly in the Thermo-Calc and DICTRA software, respectively. The results of two distinct case studies in multicomponent alloys are presented. In the first example, we simulate the isothermal growth of PE cementite in an Fe-C-Co-Cr-Mo-Ni secondary hardening steel during tempering. This is of practical importance in modeling the carbide precipitation kinetics during secondary hardening. In the second example, we have presented the results of PE ferrite growth during continuous cooling from an intercritical temperature in an Fe-Al-C-Mn-Si low-alloy steel. This is of importance to the design of triple-phase steels containing an austenite that has optimum stability, to facilitate stress-induced transformation under dynamic loading. The results of both simulations are in good accord with experimental results. The model calculations do not consider any resistive or dissipative forces, such as the interfacial energy, strain energy, or solute drag, and, as a result, the interface velocities represent an upper limit under the available chemical driving force.     

Calculation of α/γ equilibria in SA508 grade 3 steels for intercritical heat treatment

An attempt has been made to suggest an optimum temperature for intercritical heat treatment of an SA508 grade 3 steel for nuclear pressure vessels, based on thermodynamic calculation of the α/γ phase equilibria. A thermodynamic database constructed for the Fe-Mn-Ni-Mo-Cr-Si-V-Al-C-N tencomponent system and an empirical criterion that the amount of reformed austenite should be around 40 pct were used for thermodynamic calculation and derivation of the optimum heat-treatment temperature, respectively. The calculated optimum temperature, 720 °C, was in good agreement with an experimentally determined temperature of 725 °C obtained through an independent experimental investigation of the same steel. The agreement between the calculated and measured fraction of reformed austenite during the intercritical heat treatment was also confirmed. Based on the agreement between calculation and experiment, it could be concluded that thermodynamic calculations can be successfully applied to the materials and/or process design as an additive tool to the already established technology, and that the currently constructed thermodynamic database for steel systems shows an accuracy that makes such applications possible.     

Calculation of phase diagrams of systems Al-Cu-Zn-Mg and Al-Cu-Zn-Mg-Fe-Si

Fragments of phase diagrams Al-Cu-Zn-Mg and Al-Cu-Zn-Mg-Fe-Si-(Mn) in a temperature range (%) 4–6 Cu, 2–4 Zn, 0.5–2.0 Mg, 1.5–2.0 Fe, and 1.5–5.0 Si are constructed and the composition of the solid solution for a series of alloys of the Al-Cu-Zn-Mg-Fe-Si-(Mn) system at temperatures near the solidus is calculated by the results of thermodynamic calculations using the ThermoCalc software package. The thermodynamic calculations are verified by electron probe microanalysis. This verification shows the satisfactory convergence of the calculated and experimental data. It is revealed that, with the ratio of iron and silicon concentrations Fe/Si = 0.5 for alloys of the Al-Cu-Zn-Mg-Fe-Si-(Mn) system, it is possible to obtain a maximally doped solid solution.     

M-Si-B合金非晶形成能力的CALPHAD模式评估

Evaluation of the amorphous-forming ability of M-Si-B ternary alloys using CALPHAD approach@長谷部光弘$日本九州工业大学 @OHTANI Hiroshi$Department of Materials Science and Engineering, Kyushu Institute of Technology @HASEBE Mitsuhiro$Department of Materials Science and Engineering, Kyushu Institute of Technology…     

Phase Stability in the Mo-Ti-Zr-C System via Thermodynamic Modeling and Diffusion Multiple Validation

Alloys in the Mo-rich corner of the Mo-Ti-Zr-C system have found broad applications in non-oxidizing environments requiring structural integrity well beyond 1273 K (1000 °C). Alloys such as TZM (Mo-0.5Ti-0.08Zr-0.03C by weight %) and TZC (Mo-1.2Ti-0.3Zr-0.1C by weight) owe much of their high temperature strength and microstructural stability to MC and M₂C carbide phases. In turn, the stability of the respective carbides and the subsequent mechanical behavior of the alloys are strongly dependent on the alloying additions and thermal history. A CALPHAD-based thermodynamic modeling approach is employed to develop a quaternary thermodynamic database for the Mo-Ti-Zr-C system. The thermodynamic database thus developed is validated with diffusion multiple experiments and the validated database is exercised to elucidate the effects of alloying and thermal history on the phase equilibrium in Mo-rich alloys.     

Determination of isothermal transformation diagrams for sigma-phase formation in cast duplex stainless steels CD3MN and CD3MWCuN

Work was undertaken to establish reliable time-temperature-transformation (TTT) diagrams for the cast duplex stainless steels CD3MN and CD3MWCuN. The latter contains higher Cr, Ni, and Mo contents compared to the former. The TTT diagrams for sigma-phase formation in both alloys were developed based on quantitative metallography results from optical and scanning electron microscopy. The kinetics of sigma-phase were found to be much faster in CD3MWCuN alloys than in CD3MN. An Avrami analysis was employed to assess transformation characteristics and to refine the TTT diagram determination. Theoretical prediction of phase equilibria using the thermodynamic software package ThermoCalc was compared to the amount of sigma phase observed experimentally from long-term heat treatments. The constructed TTT diagrams of the cast alloys were compared to wrought counterpart alloys.     

基于原位观察的H13钢中液析碳化物高温行为研究

使用原位观察方法研究了不同凝固条件H13钢铸锭样品中液析碳化物的高温行为.实验发现连铸锭及电渣锭两种样品在所研究的枝晶间存在明显的合金元素偏析,其中Cr、Mo、V、C的偏析较为明显,液析碳化物存在于凝固枝晶间偏析最严重的区域,成分为V、Mo、Cr、Ti的液析碳化物.连铸锭及电渣锭两种样品分别在1200℃及1250℃围绕液析碳化物周围出现局部液相,理论计算的局部液相出现温度与实验观察到的接近;随着温度的升高,局部液相范围扩大,与电渣锭相比,加热至相同温度时,连铸锭液析碳化物周围的局部液相范围更大.液析碳化物周围局部液相的出现加快了枝晶间合金元素的扩散,对液析碳化物的高温行为具有重要影响.      

Phase equilibria in Cu-As(Sb,Bi)-O systems under conditions of the existence of a copper-based alloy

Solubility surfaces of components in metal melts for the Cu-As-O, Cu-Sb-O, and Cu-Bi-O systems in the range t = 1100–1300°C and high-temperature fragments of phase diagrams of oxide systems Cu₂O-R₂O₃ (R is As, Sb, Bi) are constructed based on thermodynamic calculations. Phase equilibria in the Cu-Sb-O and Cu-Bi-O systems are investigated experimentally. The results can be used to analyze the production processes of copper and copper-based alloys.