Bi-Pb-Tl三元系相图

用室温、高温X射线衍射及淬火的方法,测定了Bi-Pb-Tl三元系25℃的等温截面及该体系中的相结构。     

EFFECT OF ALLOY ELEMENTS ON QUASIEQUILIBRIUM MICROSTRUCTURE IN Fe-Mn-Ni-Cr STEELS

The microstructures of Fe-Mn-Ni-Cr steels with medium carbon and the effect of alloy ele-ments on them have been investigated by means of X-ray diffraction quantitative phase ana-lyses,metallography and hardness tests.The volume fraction of martensite in steels quenchedat 1100℃ can be expressed as:f_M~(1100)=162.643-15.482Mn-7.36Ni-4.286(Cr+Mo+V)Based on this expression,the quasi-equilibrium microstructure diagram has been obtained.Itis shown that the effect of Mn on the austenite stability is greater than that of Ni.The equiva-lent [Ni]=2.104Mn+Ni and equivalent [Cr]=Cr+Mo+V.The driving force for martensite transformation at M_s point has been calculated to hedrastically decreased by element Mn.     

QUASI-EQUILIBRIUM MICROSTRUCTURES AND EFFECT OF ALLOY ELEMENTS IN Fe-Mn-Ni-Cr STEELS

本文利用X射线定量相分析及金相观察和硬度测试,考察了中碳Fe-Mn-Ni-Cr钢的组织及合金元素的作用。建立了经1100℃淬火后的马氏体体积分数与合金成分的定量关系式; f_M~(1100)=162.643-15.482Mn-7.36Ni-4.286(Cr+Mo+V)并在此基础上给出了亚平衡组织图。结果表明,Mn稳定奥氏体的作用大于Ni的作用。Ni和Cr当量分别以[Ni]=2.104Mn+Ni,[Cr]=Cr+Mo+V表示。计算了M_S点处的马氏体相变驱动力,指出Mn具有强烈降低相变驱动力的作用。     

Thermodynamic study of the phase equilibria in the Sn−Ti−Zn ternary system

The Sn−Ti−Zn ternary phase diagram has been constructed using the CALPHAD technique. The Ti−Zn binary system phase boundaries were determined using differential scanning calorimetry and the solid-liquid diffusion couples method. In addition, the formation energy of some stoichiometric compounds was obtained using first-principle band energy calculations. For the ternary system, some alloys were prepared by equilibration at 600 or 700 °C, and the compositions of the precipitates were analyzed using electron probe microanalysis. Thermodynamic assessment of the Ti−Zn and Sn−Ti−Zn systems was performed based on the experimental information and by adopting reported values of the thermodynamic properties of the Sn−Zn and Sn−Ti binary systems. Microstructural observation showed that Sn₃Ti₅Zn₁₂ exists in the ternary system. Seven types of invariant reaction on the Sn-rich liquidus surface of the ternary system are predicted by the phase diagram calculations. The ternary eutectic point falls at 0,0009 mass% Ti and 8.69 mass% Zn, at T=192.40°C, which is slightly lower than the calculated eutectic point of Sn−Zn binary alloy (T=192.41°C). Based on these results, a nonequilibrium solidification process using the Scheil model was simulated. This paper was presented at the International Symposium on User Aspects of Phase Diagrams, Materials Solutions Conference and Exposition, Columbus, Ohio, 18–20 October, 2004.     

Kinetics of hydrogen absorption and desorption of magnesium nickel alloy

Reaction rates in the Mg₂Ni---H₂ system are still unclear, although they are needed for the process/optimization of hydrogen storage reactors. In this article, the rates of hydrogen absorption and desorption of the magnesium nickel alloy were investigated at different pressures up to 2.0 MPa using a constant-temperature thermogravimetric method. The powder of the alloy was microencapsulated with copper to improve the alloy properties (such as cycling strength) as a pretreatment. In the experiments, weight changes of the smallest amount possible of samples were monitored with the help of an ultra-accurate thermobalance, in order to avoid changes of the sample temperature due to the heat of the reaction. The reaction curves obtained revealed unique dependence of temperature and pressure and influence of thermal hysterisis. It is also possible that hydrogen-absorption and-desorption rates of this hydrogen storage alloy are expressed by the rate equation of first-order reversible reaction.     

EQUILIBRIA OF SYSTEM MoO_3-MoO_2-H_2O-H_2 AND PHASE DIAGRAM FOR SYSTEM Mo-O BETWEEN 400 AND 700℃

使用自行设计的受控气氛热重装置研究了MoO_3—MoO_2-H_2O—H_2系平衡.在P_(H_2O)/P_(H_2)从0.412至0.609,温度从400至534℃范围内直接测定了反应:MoO_3+H_2=MoO_2+H_2O(g)的平衡常数与温度间的关系为1gK_p=0.702-739.8/T获得298.15K下MoO_3标准生成焓及绝对熵分别为:-845.75kJmole~(-1)及78.1 J·K~(-1)mole~(-1) 实验表明,存在于MoO_2-MoO_3系中的一些Magneli相在本研究条件下不能作为热力学稳定相而存在.并绘制了400-700℃下Mo-O系相图.     

Nd—Pd—Ru三元系富钯区域的相图

用Ｘ射线衍射和金相显微镜分析方法研究了Ｎｄ－Ｐｄ－Ｒｕ三元系的富钯区域，作出部分相图的７００℃等温截面。发现Ｒｕ在（ＮｄＰｄ３）中有高达１３ａｔ％的固溶度。该截面上存在４个单相区：（Ｐｄ），（Ｒｕ），ＮｄＰｄ５和ＮｄＰｄ３；５个二相区：（Ｐｄ）＋（Ｒｕ），（Ｐｄ）＋ＮｄＰｄ５，ＮｄＰｄ５＋ＮｄＰｄ３，ＮｄＰｄ３＋（Ｒｕ）和ＮｄＰｄ５＋（Ｒｕ）；２个三相区：（Ｒｕ）＋ＮｄＰｄ３＋ＮｄＰｄ５和（Ｐｄ）＋（Ｒｕ）＋ＮｄＰｄ５。     

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.     

Metallochemical Analysis of the Reaction in a Mixture of Nickel and Aluminum Powders

Phaseformation processes are considered at the level of a mesocell of a mixture with the use of the state diagram for a binary system. Consecutive schemes of metallochemical reactions of formation and decomposition of intermetallide compounds in a mixture of nickel and aluminum powders are suggested. The problem of diffusion annealing of this mixture is numerically solved for two different conditions: at a constant temperature and at a temperature slowly increasing by a linear law.