Misfit strain energy in the Au-Cu system

Misfit strain energy has been calculated for the AuCu lattice from interatomic distances and the Morse function; the calculations give results of the same order of magnitude as calculations from elasticity theory. It is shown that electronic rearrangements occur during uniaxial tension, greatly reducing the strain energy from that calculated by ordinary methods. The theory of Pauling is applied and the electronic rearrangements derived from this theory reduce the strain energy to small values. This is not true, however, in other lattices. An explanation is advanced as to why Au-Cu alloys form more exothermically than Au-Ag alloys.     

Fe－1．83C马氏体调幅分解的TEM研究

利用透射电镜研究了Ｆｅ－１．８３Ｃ（％）马氏体在室温时效后衍时斑点的漫散射及显微组织变化。利用双倾试样技术得出了漫散时斑强度在倒易空间的分布。结果表明：马氏体斑点呈漫散的角状，其立体形态由对顶的两个四棱锥构成对漫散射的Ｆｏｕｒｉｅｒ分析及ＴＥＭ显微组织分析表明：马氏体在时效时发生了调幅分解，其调幅结构由波长为≈１ｎｍ的主波和波长大于１ｎｍ的次波叠加而成；同时发现Ｆｅ－Ｃ马氏体调幅分解的一个显著特点是，调幅结构时效数月后也未长大。对马氏体正方度的研究表明：在调幅分解过程中碳原子的再分布仅限于Ｏ＿ｚ八面体间隙亚点阵中。     

添加Mn和Ce对Ti0.27Cr0.33V0.4合金储氢性能的影响

采用XRD、SEM/EDS和PCT测试等方法,研究了添加Mn和Ce对于(Ti0.27Cr0.33V0.40)100-xMnxCey合金的组织结构和储氢性能的影响。结果表明:Mn的添加促进了富Ti相的析出,减小了合金bcc主相的晶格常数,平台压升高,残余氢量减小,当Mn含量为8at%时其有效储氢量达到最大值,在此基础上添加Ce,有效抑制了富Ti相的析出,促进了合金成分的均匀分布,增大了合金的晶格常数,改善了合金的平台性能,提高了合金的最大吸氢量和有效储氢量。     

First-Principles Investigation on Electronic Structure and Optical Properties of Wurtzite InxGa1-xN Alloys

采用密度泛函理论框架下的第一性原理平面波超软赝势方法,研究In掺杂对纤锌矿InxGa1-xN合金的晶格常数、能带结构、态密度和光学性质的影响。计算结果表明：随着In掺杂浓度的增加,晶格常数逐渐增大,导带向低能方向移动,带隙变窄;与此同时,介电函数向低能方向发生了漂移,发生了红移现象。在2.0 eV附近出现了第一个介电峰,在4.76 eV附近出现了最大的介电峰。在大约5.6 eV和9.2 eV处有两个交叉点,当光子能量低于5.6或者高于9.2 eV,低掺杂浓度(小于50%)的吸收系数小于高掺杂浓度的吸收系数;当光子能量在5.6到9.2 eV之间,低掺杂浓度的吸收系数高于高掺杂浓度的吸收系数。研究结果表明InxGa1-xN合金可以作为太阳能电池以及透明导电薄膜的材料     

Site occupancy in ternary L12 ordered alloys as determined by diffraction: observations on (Al,Cr)3 Ti alloys

The nature and occurrence of point defects have been studied in L1₂ ordered (Al,Cr)₃Ti alloys. Four compositions were investigated, two stochiometric alloys with either 9 or 12 at. pct. Cr, and two nonstoichiometric alloys with 10 at. pct. Cr and either 23 or 27 at. pct. Ti. Measurements of lattice parameter, density, and composition were combined to calculate the average number of atoms per unit cell. No variation in this quantity was detected with alloy composition, suggesting that the dominant point defects in these ordered phases are antisite defects rather than constitutional vacancies. A lack of constitutional vacancies was further supported by comparisons of measured and calculated superlattice peak intensities. The common method of regression fitting calculated and measured X-ray diffraction intensities using a single wavelength is shown to be unable to define the two independent order parameters unambiguously, calling into question the results of such previous studies on these ternary alloys. Only if an assumption is made that one type of site substitution dominates the antisite formation can the method be used to estimate the solution for the dominant behavior. Assuming that one type of substitution dominates the antisite formation on β (Ti) sites, the measurements performed in this study suggest a small amount of Cr, but not Al, substitution on β sites, and that most of the Cr is on α (Al) sites. Increasing the Cr level in stoichiometric alloys causes more Cr to occupy β sites, displacing some Ti to α sites, thus creating more antisite defects. The Ti deficiency in hypostoichiometric alloys is alleviated by enhanced substitution of Cr on β sites. However, the excess Ti in hyperstoichiometric alloys greatly decreases any Cr substitution on β sites.     

Mechanical properties and bonding feature of the YAg,CeAg, HoCu,LaAg, LaZn,and LaMg rare-earth intermetallic compounds: An ab initio study

Full-potential linearized augmented plane wave (FLAPW) method has been employed within the generalized gradient approximation (GGA) to investigate structural and elastic properties of YAg, CeAg, HoCu, LaAg, LaZn, LaMg compounds. The calculated ground state properties such as lattice constants, bulk Modulus and elastic constants agree well with the experiment. The ductility or brittleness of these intermetallic compounds is predicted. The calculated results indicate that LaAg is the most ductile amongst the present compounds. For HoCu and LaZn compounds, the mechanical properties and Debye temperature are predicted from calculated elastic constants. In addition, chemical bonding of these compounds has been investigated in the light of topological analysis approach based on the theory of atoms in molecules.     

Monte Carlo simulation of phase separation in iron-based ternary alloys

Numerical simulations of phase separation in Fe–Cr–Mo ternary alloys were performed with use of a model based on the Monte Carlo simulation, in order to investigate mechanisms of phase separation in Fe-based ternary alloys. Cr-rich regions were formed in an Fe–40at.%Cr–5at%Mo alloy. Mo atoms enrich into the Cr-rich region and/or boundaries of Cr/Fe rich regions. Behaviors of Mo and Cr in an Fe 40at.%Mo–5at.%Cr alloy were similar to those in the Fe–40at.%Cr–5at.%Mo alloy. The first peak position of the structure factor moves on to the shorter side of the wave number with the increase of temperature. Analysis of the static structure factor of a minor element indicates that the bifurcation formation of concentration profile of the minor element occurs at peak positions of the major element which is predicted by a theory based on the Cahn-Hilliard equation.     

粉末冶金Al-1．1Sc和Al-2SC合金晶体结构的实验和第一性原理研究

采用气体雾化合金颗粒制备Al-1．1％Sc和Al-2％Sc合金。采用x射线衍射分析合金样品以确定样品的晶格参数。利用这些晶格参数,分别通过WIEN2K和EMTO程序对该合金的力学性能进行理论计算。将实验得到的合金的弹性模量和理论计算结果进行比较。讨论了计算得到的A13Sc相和AI—Sc合金的力学性能以确定Al-Sc合金中最佳的Sc含量。结果表明,最高的Sc含量约为1．0％,更多的Sc不能提高合金的力学性能。     

共格沉淀析出过程的模拟Ⅰ--微观结构演化

采用相场模型对共格沉淀析出过程微观结构演化进行模拟研究.模拟结果表明,应力场的存在将会对相变过程中析出相形态产生显著的影响,通过界面能与弹性应变能的相互竞争析出相在不同阶段呈现不同的形态如模量结构、网格结构、三明治多畴结构、沉淀宏观点阵结构以及板条状等;此外,点阵错配度中等(2%～4%)时,粒子的粗化过程将出现应力诱导反向粗化现象,这种粗化现象取决于粒子的点阵错配度与体积分数.     

Valence bond structure of Ta-W alloys

The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal(CC)theory.This theory is based on cluster statistics of random alloys.By studying the correlativity between energy and volume of the CC in Ta-W alloys,the valence bond structure of CC is determined by the energy and shape method.Then,following additive law of CC,the valence bond structure of Ta-W alloys is calculated.It is found that the outer shell valence electronic distribution of Ta-W alloys shows ...     

Precursor of the virtual β phase in the topography of the electron density of the α-Ti<Subscript>13</Subscript> nanocluster

The scattered-wave method is used to calculate the energy spectrum and wave functions of electrons in clusters of α-Ti and its alloys with B, C, and N. A clear asymmetry in the distribution of electron density is revealed, which distinguishes groups of four and two atoms in the basal plane of the hcp structure, which correspond to the coordination of nearest and next-nearest neighbors in the (110) plane of the β phase.     

Influence of electronic structure on Compton scattering through comparing Cu-Ni alloys with Cu-Ni powder mixtures

The application fields of Compton scattering have been further broadened through the studies of theories and experiments as well as the electronic structure of the scatters. The relationship between the contents of binary alloys (also binary powder mixtures) and the number of Compton scattered photons has been thoroughly examined. The linear expression of the relationship has been obtained approximately according to the Compton scattering theory. And the relationship has been validated well through the Compton scattering experiments with the scatters of Cu-Ni binary alloys or Cu-Ni binary powder mixtures. Furthermore, it is found that the slope of Cu-Ni powder mixture series is steeper than that of Cu-Ni alloy series, and through the pseudopotential plane wave theory of DFT the microscopic principles of Compton scattering of Cu-Ni alloy and Cu-Ni powder mixture series have been discussed and compared with each other. The results show that the electronic structure is the main reason for the difference of the linear slopes, and the line slope of Cu-Ni powder mixtures series is steeper than that of Cu-Ni alloy series.     

VQ2(Q=H, D, T)热力学氢同位素效应的理论研究

基于量子力学第一性原理,采用赝势平面波函数与密度泛函结合的方法,计算并研究V、VH2、VD2、VT2体系的晶格动力学特征及热力学函数,采用热力学方法分析钒吸氢生成VQ2(Q=H,D,T)的热力学同位素效应。晶格动力学性质研究表明,VQ2的热力学同位素效应主要是氢同位素在钒晶格中的振动频率不同导致的。VQ2生成反应在10～1000K的温度范围内标准吉布斯自由能变由-50kJ·mol-1近似线性上升至140kJ·mol-1。平衡压力与温度关系表明,在高于常温的条件下,平衡压力随温度急剧升高;钒吸附氢同位素生成二氢化钒在整个温度范围内均表现为负同位素效应。     

STRUCTURAL TRANSFORMATION INDUCED BY MECHANICALLY DRIVEN ALLOYING AND SUBSEQUENT MAGNETIC PROPERLIES OF THE Fe-Cu SYSTEM

1.IntroductionRecently,someworkshavebeenfocusedonthemechanicalalloyingofFeandCupowders[1--61.ThemagneticpropertiesofFe-Cualloyssuchassaturationmagnetization,coercivityandCurietemperatureasafunctionofthecomposition,temperatureorthemillingtimehavebeenreported[1,2,6--12].Furthermore,thevariationsofthemagneticpropertiesagainstannealingtemperaturesortimeshavealsobeen.otic.d[8'13--16].Inthispaper,thestructuraltransformationinducedbymechanicallydrivenalloyingisstudiedbytakingFe6oCu4oasanexample.S…     

Enthalpies of formation for the Al–Cu–Ni–Zr quaternary alloys calculated via a combined approach of geometric model and Miedema theory

A method to extrapolate the thermodynamic properties of quaternary alloys from constitutive binary systems is presented. The method is based on Miedema's theory, and the asymmetry of thermodynamic properties of constitutive binary alloys is considered in the present model. The dependence of asymmetric constituent on the choice in Toop model has been overcome. This method has been applied to calculate the enthalpies of formation for ternary alloys. In the present work, the proposed method is used to calculate the mixing enthalpies of Al–Cu–Ni–Zr quaternary alloys and its constitutive subsystems. The good agreement between calculation and experimental data indicates that the present method is reasonable for predicting the thermodynamic properties of multi-component system.     

Atom configurations in Pd–Au and Pd–Au–D alloys: A neutron total scattering and Reverse Monte Carlo study

The effect of the alloying elements on the distribution of deuterium in Pd–Au has been investigated by total neutron scattering. The data are analyzed by Reverse Monte Carlo modeling in order to assess the type of interstitial sites occupied with deuterium and how this is correlated with the distribution of the Pd and Au atoms on the host metal lattice. The results show that in Pd–Au alloys deuterium occupies both octahedral and tetrahedral interstitial sites: the overall occupancy of tetrahedral sites increases with increasing Au content and decreasing overall D content. Short-range ordering (SRO) is identified in the D occupancy of interstitial sites in the sample with higher Au content. Indications of SRO and D-induced reorganization in the metal lattice are discussed.     

空位缺陷对单层MoS_2电子结构的影响

为了研究单层Mo S2中的空位缺陷形成及其对电子结构的影响,基于密度泛函理论框架下的第一性原理,采用平面波赝势方法分别计算了单层Mo S2中Mo空位和S空位的形成能、空位附近的晶格畸变、Mo S2层中的电子分布以及态密度(DOS)和能带结构。计算结果显示,2种空位缺陷都具有点缺陷特征,其附近的电子分布呈现出明显的局域化特点,且S空位比Mo空位更容易形成。通过与本征态Mo S2电子结构的对比分析,发现2种空位缺陷的存在对单层Mo S2的电子结构、尤其是对导带高能量区域的能态密度会产生十分明显的影响,这些影响可能与空位缺陷引入的缺陷能级有关。     

Zr含量对Al3(ZrxEr1-x)相价电子结构与合金性能的影响

用固体与分子经验电子理论(EET)计算研究了微量元素Er,Zr添加到铝合金中产生的Al3Er和Al(ZrIxEr1-x)相的价电子结构,探讨了不同Zr含量对Al3(ZrxFr1-x)相各电子结构参数的影响.计算结果表明:随着Zr原子含量的增加,表征强度性能的最强键上的共价电子对数na和相结构形成因子S会减小,这说明合金...     

TMAl(TM=Ir、Ru和Os)金属间化合物高压下力学性能的第一性原理研究

采用第一性原理方法研究了TMAl (TM=Ir、Ru和Os)三种金属间化合物在高压下晶格常数、弹性常数和弹性模量的变化规律。结果表明,三种金属间化合物的晶格常数和晶胞体积随着压力的增加而减小。通过对TMAl金属间化合物弹性性质的分析,发现它们的弹性系数和弹性模量随着压力的增加几乎呈线性增大。这主要是由于在压力的作用下,体相中TM原子和Al原子的相互作用增强,TM-Al金属键的键长变短所导致的。此外,三种金属间化合物在常压下表现为塑性行为,并随着压力增加而进一步增强。IrAl的普适弹性各向异性接近于零,表明其具有较好地抵抗微裂纹产生的能力。     

Formation of texture in thin tapes of Fe-Ni alloys during cold rolling and recrystallization

A quantitative analysis of rolling textures in iron-nickel alloys with a wide range of concentrations of the alloying element has been performed by analyzing the orientation distribution function. It has been found that, despite a considerable increase in the lattice parameter of the alloys under study, their deformation texture is similar to the deformation texture of pure nickel, making it possible to produce a perfect cube texture after primary recrystallization. It has been shown that the use of two-step annealing allows improving the sharpness of the cube texture in the iron-nickel alloys studied.