锡对铝锌镁铜合金在120℃时效后组织与性能的影响

采用透射电子显微镜和维氏显微硬度计研究了锡对铝锌镁铜合金在120℃时效不同时间后组织和性能的影响。结果表明:时效初期,锡能促进GP II区的形成;含锡合金中锡的高空位结合能影响了元素的扩散,导致η′相的粗化被抑制,从而延迟了硬度峰值的出现,而且合金具有更高的硬度。     

Fe-Ti二元体系的热力学重新优化(英文)

为提高Fe-Ti二元系外推到三元或多元体系的能力,应用CALPHAD方法重新优化了该二元系。与前人的优化工作相比,重点放在对两个二元金属间化合物Fe2Ti和FeTi的热力学描述上。因目前普遍采用双亚点阵模型来描述C14_Laves相,所以采用双亚点阵模型来描述Fe2Ti相。通过检验包含Fe-Ti二元系的三元体系Fe-Ti边界上Fe2Ti相的均匀化范围进一步证实了Fe2Ti相的相边界。FeTi相具有BCC_B2晶体结构,因而将其处理成为BCC_A2相的有序相,并且用统一的Gibbs 能函数来描述有序和无序相。另外一个特别关注的方面就是重现这两个化合物的实测热容。计算结果与有关相图和热力学性质实验结果的广泛对比显示两者符合得很好,从而证明了所得热力学描述的有效性。     

Thermodynamic assessment of Cu-Cd system

A thermodynamic assessment of the Cu-Cd system has been carried out by CALPHAD technique.The liquid phase, FCC_A1(Cu)and HCP_A3(Cd)terminal phases are described by a simple substitutional model,their excess Gibbs energy is formulated with the Redlich-Kister expression.The system contains four intermediate compounds,includingβ(Cu2Cd),γ(Cu4Cd3), δ(Cu5Cd8)andε(Cu3Cd10).Theδphase is described by a two-sublattice model and the other three intermediate phases are treated as stoichiometric phases.The optimization is carried out in the Thermo-Calc package.A set of self-consistent thermodynamic parameters are obtained.The calculated phase diagram and thermodynamic properties agree well with the available experimental data.     

Transformations and phase relations in Nb—Ti—Si ternary system at 1373—1473K

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Experimental determination and Re—optimization of Ni—Ta binary system

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THERMODYNAMIC OPTIMIZATION AND CALCULATION OF THE Fe-Pr SYSTEM

Based on the phase diagram of the Fe-Pr system available,the thermodynamic optimization and calcula-tion of the system have been carried out by the least square method.The lattice stabilities of Fe and Pr aredescribed by the expression recommended by SGTE organization.The liquid phase is described by thesubregular solution model.The intermetallic compounds,Fe_(17)Pr_2 and Fe_2Pr,are treated as stoichiometriccompounds.The optimized parameters describing phases in the system are presented.The comparision be-tween the calculated and experimentally determined phase diagram shows that the agreement is generally verygood except for the liquid δ-Fe equilibrium.It is suggested to measure this part of phase diagram again.     

A Study of the Isothermal Section in the W-Fe-Co Ternary System at 1380K

The purpose of the present paper isto determine the composition range ofthe θ intermediate phase and establishthe phase equilibria relation in theW-Fe-Co ternary system.The experimentalresult was compared with the calculationof phase diagrams in Guillermet's work.1.Experimental ProcedureThe diffusion couple specimen usedin this investigation was prepared fromthe tungsten bar (99.96 wt-%),electro-     

ISOTHERMAL SECTION OF THE W-Ni-Cu SYSTEM AT 1017℃

采用扩散偶试样,借助电子探针、X射线衍射等分析方法,测定了W-Ni-Cu三元系1017℃等温截面。在该温度下,W-Ni二元系存在体心四方结构的Ni_4W和正交结构的NiW,没有观察到NiW_2。钨在Ni_4W中的固溶度范围为16.95—20.51at.-％(39.00—44.70wt-％),Cu在Ni_4W中的固溶度范围为0—4.36at.-％(3.40wt-％).钨在γ(Ni)固溶体中的最大固溶度为13.11at.-％ (32.10wt-％).     

Thermodynamic optimization of Mg-Nd system

Based on the reported experimental data,the phase diagram of Mg-Nd binary system was optimized using the CALPHADapproach.Gibbs energies of the disordered BCC_A2 and ordered BCC_B2 phases were modeled with a single expression based on a2-sublattice model.Liquid and terminal solutions,such as dHCP and HCP,were modeled as substitutional solutions.Intermediatephases Mg2Nd,Mg3Nd and Mg41Nd5 were treated as stoichiometric compounds.The optimization was carried out in theThermo-Calc package.A set of thermodynamic parameters is obtained.Calculated phase diagram,enthalpies of formation and Gibbsenergies of formation are in reasonable agreement with the experimental data.     

Determination of isothermal sections of Ni-Cr-Nb ternary system

The isothermal sections of Ni-Cr-Nb ternary system at 1 323 K and 1 423 K were determined by means of diffusion triple and energy spectrum analysis (ESA). By analyzing the diffusion layers in the diffusion couples, the compounds forming in this system were identified. There are three similar compounds found at these two temperatures: Ni3 Nb, NiNb and NbCr2-R, and four similar three-phase regions are found : (Ni) (Cr) Ni3 Nb, Ni3Nb NbCr2-R NiNb, NbCr2-R (Cr) Ni3 Nb, NbCr2-R NiNb (Nb). The results show that no phase transformation happens between these tow temperatures. But the solid solubilities of the binary compounds at 1423 K become bigger than those at 1 323 K, especially the solid solubility of NbCr2-R. No ternary compound is observed.