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调整了MAEAM模型中的电子密度参数比,并以相图为基础考虑每个成分比的相结构,应用改进分析型嵌人原子方法(MAEAM)计算了TiAI合金形成热.计算结果与Miedema理论结果进行了比较,二者的变化趋势一致.为了说明计算方法的可靠性,用同样的方法计算了NiAl合金和FeAl合金形成热.模拟结果与实验结果和第一性原理计算结果相一致. 相似文献
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金属铑的原子状态、物理性质和热力学性质的研究 总被引:3,自引:0,他引:3
依据纯金属单原子理论(OA)确定了面心立方结构(fcc)金属Rh的原子状态为[Kr](4dn)4.46(4dc)2.54(5sc)1.61(6sf)0.39,并对金属Rh的密排六方结构(hcp)和体心立方结构(bcc)初态特征晶体及初态液体的原子状态进行了研究,在此基础上解释了Rh的原子状态与晶体结构的关系,通过计算得到了fcc-Rh的势能曲线,线热膨胀系数、晶格常数和结合能等物理性质随温度变化的曲线,同时计算了fcc金属Rh的比热、熵、焓和Gibbs能等热力学性质随温度变化关系的曲线,这些性质理论值与实验值符合较好,为电催化剂及相关材料的优化设计提供了理论指导。 相似文献
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以3.0 mol/L HNO3活化后的三钛酸钠晶须为吸附剂,以电感耦合等离子体原子发射光谱(ICP-AES)法为检测手段,探讨了静态条件下三钛酸钠晶须对Cu(Ⅱ),Co(Ⅱ),Pb(Ⅱ)的吸附和解脱行为,考察了影响其吸附和解脱的主要因素、三钛酸钠晶须对Cu(Ⅱ),Co(Ⅱ),Pb(Ⅱ)的吸附等温线及三钛酸钠晶须对其它几种离子吸附的情况。结果表明:在pH5.0下,0.250 0 g的三钛酸钠晶须对上述3种离子的吸附效果最好;在沸水浴中,以10 mL 3.0 mol/L的HCl作解脱剂,可实现3种离子的定量解 相似文献
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应用电导法测定了298K时DyCl3在混合溶剂(DMF-H2O)中的活度系数和电导率,利用公式计算了DyCl3的摩尔电导率,应用Debye-Hücker和Osager-Falkenhangen公式计算了DyCl3在混合溶剂(DMF-H2O)中的活度系数,并讨论了在298K时浓度对DyCl3溶液活度系数的影响,随氯化稀土溶液浓度增加,稀土盐溶液的活度系数降低.计算了DyCl3在混合溶剂中的相对偏摩尔自由能,对其相对偏摩尔自由能的某些变化规律作了初步的讨论. 相似文献
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采用石墨坩埚浇铸法在真空中频感应熔炼炉中制备Zr55Al10Ni5Cu30合金,并对合金进行了金相、X射线衍射和显微硬度的测试,考察原料纯度、过热度及冷却速率对非晶态合金性能的影响。结果表明,采用工业级原料就可以制备出性能良好的非晶态合金,在低的冷却速率下形成的非晶态合金具有相对较高的硬度,适当提高过热度可以减少微晶的形成。 相似文献
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采用静态吸附法,研究了D113离子交换树脂吸附锰(Ⅱ)的过程和机理。结果表明:在一定的浓度范围内,D113树脂对锰(Ⅱ)的吸附符合Langmuir和Freundlich等温吸附方程式,但Langmuir方程更能准确反映该交换吸附过程。热力学函数ΔH0,表明吸附为放热反应,降低温度有利于吸附进行;ΔS0,说明吸附过程熵减少占主导作用;ΔG0,表明该吸附过程为自发过程。吸附交换过程符合HO准二级吸附交换动力学方程,表观吸附活化能Ea为35.085 kJ/mol,颗粒扩散过程为吸附的控速步骤。 相似文献
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本文对Gd0.97V0.03合金的硬度、抗拉强度、耐腐蚀性以及相关机理进行了研究。研究发现:Gd0.97V0.03合金硬度和抗拉强度分剐为86.2HV和205MPa,相比Gd分剐提高了40%和12%;相同的腐蚀时间下,Gd0.97V0.03合金的腐蚀量和腐蚀速度在开始时高于纯Gd.但经过1天左右水腐蚀后,其腐蚀量和腐蚀速度明显低于纯Gd,Gd0.197V0.03合金腐蚀层产物主要为Gd的氧化物Gd2O3,以上结果表明该系列材料有望成为良好的室温低场磁制冷工质。 相似文献
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研究了微量硼和 2 % Nb对铸造 Ni5 0 Al2 0 Fe30 合金组织及性能的影响。结果表明 :微量硼的加入可以改善 Ni5 0 Al2 0 Fe30 合金的强度与塑性 ,最佳硼含量为 0 .0 2 %~ 0 .0 5 % ;此外 ,微量硼的加入影响该合金的共晶区 ,从而明显改变合金的微观组织形态。在硼含量为 0 .0 2 %时 ,该合金主要处于 β相 (Ni Al)与 γ相的共晶区 ,这对合金的室温塑性极为有利。添加 2 % Nb可明显提高该合金的压缩屈服强度并改善塑性。在室温、6 5 0℃和 10 0 0℃ ,该合金的压缩屈服强度分别提高 30 %、5 9%和 36 % 相似文献
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The time and temperature dependence of wetting Cu and Ag substrates by molten 60Sn40Pb drops was determined using several
fluxes. Four stages were identified. In Stage I, the solder melts and develops into a spherical cap, which spreads rapidly
to the quasi-equilibrium stage II, wherein the contact angle θ changes only slightly with time. This is followed by stage
III, where6 decreases with a time exponent of ≈0.2, leading ultimately to stage IV, where θ again changes only little with time. An intermetallic
compound was observed at the liquid/solid inter-face throughout stages II to IV. The flux influenced the magnitude of θ and
the small time dependence in stage II. For a nonactivated rosin flux, the temperature dependence of θII yielded an apparent activation energy QII
a = 2 to 3 kcal/mole for all substrates, including pretinned Cu. It is speculated that the driving force for the decrease in
θ during stage III may result from a decrease in the free energy of the system by diffusion, with a corresponding change in
one or more of the interfacial tensions. Pretinning Cu, which formed the intermetallic compound Cu3Sn on the surface, had
a significant effect on the time dependence of θ, the effect in stage II being relatively greater than in stage III. 相似文献
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NiAl应力诱发马氏体相变的分子动力学模拟 总被引:2,自引:0,他引:2
利用NiAl合金的嵌入原子势,通过分子动力学模拟方法研究了标准化学计量比NiAl合金中应力诱发马氏体相变的微观机理。系统径向分布函数的变化表明,模拟中发生了B2结构奥氏体逐渐转变为四方L10结构马氏体的相变,分析了马氏体形核和长大过程中系统微观结构的变化规律。通过分析形核前后系统应变的变化过程,探讨了应力诱发马氏体形核的微观机理。 相似文献
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Levashov E. A. Mishina E. S. Malochkin O. V. Stanskii D. V. Mour J. J. Fadeev M. I. 《Metallurgist》2003,47(3-4):133-139
This article examines aspects of the effect of nanocrystalline powders of ZrO2, Al2O3, W, WC, WC–Co, NbC, and Si3N4 on the combustion, structure, and physical and physico-mechanical properties of new dispersion-hardened electrode alloy TiC – 40%KhN70Yu. This heat-resistant hard alloy, based on titanium carbide and a nickel alloy, was obtained by self-propagating high-temperature synthesis (SHS). It is shown that the addition of a nanocrystalline powder decreases combustion rate, with the magnitude of the reduction depending on the specific surface of the addition. It was determined that the structure of the synthesis products is modified appreciably by introducing a mixture of nanocrystalline powders into the initial charge. Here, additions of ZrO2 and NbC have a positive effect on the main physico-mechanical characteristics of the alloy (strength, hardness, fracture toughness). Nano-powders of Al2O3 and Si3N4 have a negative effect on the alloy's physico-mechanical properties. The addition of WC–Co increases the flexural strength of the material, while the addition of W and WC increases its fracture toughness. 相似文献
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对粉末冶金法制备的Mo-30Cu合金板材,在不同工艺条件下进行轧制试验,采用金相显微镜及扫描电镜对轧制变形后的组织进行观察,并采用维氏硬度计对经过不同道次变形量的材料进行硬度测试,研究合金的轧制变形性能及组织演变.研究发现,热轧温度为900℃、变形量达到50%时,板材试样轮廓清晰,Mo颗粒被压扁拉长,呈椭球状,烧结态组织转变为变形组织.总变形量为98%的Mo-30Cu合金箔材组织中,Mo相与Cu相均被压成纤维状,两相成均匀层叠分布,Mo层与Mo层、Mo与Cu层间界面清晰,彼此结合紧密.Mo-30Cu合金的轧制变形行为分为3个阶段:总变形量小于50%时,Mo颗粒在Cu相中滑移及Cu相变形;变形量介于50%~90%时,Mo相和Cu相协调变形:变形量大于90%时,Mo相变形.经热轧变形后的Mo-30Cu合金,当冷轧变形量为0%~ 25%时,由于加工硬化,维氏硬度呈直线上升;当冷轧变形量大于25%时,随着变形量的增加,钼骨架和铜相逐渐变形形成纤维组织,位错密度的增长趋势逐渐减弱,加工硬化效应也会逐渐低于线性增长规律,同时晶格畸变能增加,产生变形热效应,促使材料中产生回复过程,材料的硬度增加缓慢. 相似文献
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根据Miedema模型,计算了Mg-Sc合金液态和固态时的生成焓.结合相关的热力学关系式,计算了该合金中Sc的活度曲线,并拟合了该合金的相互作用系数,发现本文所采用的Miedema模型和正规溶体模型对于Mg-Sc合金是适用的. 相似文献
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The compressive creep and stress-strain behavior of the near-eutectic 60Sn-40Pb solder alloy has been investigated over the
temperature range of −55 °C to 125 °C. The total primary creep strain is a strong function of stress and temperature: at lower
temperatures and high applied stresses (i.e., near the power-law breakdown regime), it is quite large, while it is much smaller at higher temperatures and lower applied
stresses. The compressive minimum creep rate as a function of stress and temperature is fit well by the Garofalo sinh equation.
A discussion of the effective stress exponent, n
eff, in the context of the Garofalo sinh equation is presented to understand trends in the creep data. The values of n
eff, for the applied stress levels studied, are found to range from 3.09 to 5.00 at 125 °C, while they have a range of 10.75
to 15.79 at −55 °C. These trends are consistent with the interpretation of climb-dominated creep at higher temperatures and
plasticity-dominated power law breakdown behavior at the lower temperatures. The microstructural observations suggest that,
at elevated temperatures, deformation occurs by relative displacement of eutectic colonies in the solder microstructure accompanied
by extensive grain coarsening in the colony boundaries. At lower temperatures (<0 °C), deformation occurs by cell displacement
with very limited coarsening and, at high stresses, is dominated by plastic deformation. The application of the Garofalo sinh
equation to other data sets for creep of eutectic Sn-Pb solder is also discussed. 相似文献