钨合金强化机制的电子结构表征

结合固体与分子经验电子理论（EET）和改进的TFD理论计算了不同成分钨合金的相空间及相界面处的价电子结构。结果表明,钨合金的强化机制与粘结相的价电子结构有着密切的关系。相对于纯钨,粘结相的共价电子个数有所增加,相界面处的电子密度和界面上可能的原子状态组数也大大提高,且降低了钨颗粒之间的连接,这是钨合金强化的本质原因。     

反应合成AgSnO2材料的显微组织和力学性能研究

采用一种新的工艺(反应合成法)制备了AgSnO2电接触材料，并对AgSnO2材料进行了显微组织和力学性能研究。结果表明：采用反应合成技术可以在Ag基体中合成尺寸细小、界面新鲜的SnO2颗粒，微米级的SnO2颗粒是由纳米级的SnO2颗粒聚集而成。由于SnO2颗粒在Ag基体内部通过反应原位获得，增强了sn02颗粒与Ag基体的界面结合能，改变了Ag和SnO2的结合状态，使AgSnO2材料的加工性能和力学性能得到改善和提高。     

Mg-Zr合金固溶体的价电子结构分析

基于固体与分子经验电子理论(EET),分析了Mg-Zr合金固溶体的价电子结构,计算了表征合金力学性能的价电子结构参数(VESP)最强共价键上共用电子对数统计值(n'A),晶胞中可能存在的原子状态组数(σN),相界面上共价电子密度差统计值(Δρ')及相界面中可能存在的原子状态组数(σ)。结果表明:Mg-Zr合金固溶体晶胞的最强共价键上共用电子对数统计值(n'_A~(Mg-Zr))值为0.12984,明显大于纯Mg中对应的数值(0.10991),相应的原子状态组数σ_N~(Mg-Zr)(9)σ_N~(Mg)(1),表明Zr元素固溶产生了显著的固溶强化效果。而合金固溶体中各相界面上共价电子密度差统计值的关系为Δρ'~(Mg/Mg-Zr)=16.5541Δρ'~(Mg-Zr/Mg-Zr)=3.8673Δρ'~(Mg/Mg)=0,相应的的原子状态组数σ_(Mg-Zr/Mg-Zr)=45σ_(Mg/Mg-Zr)=9σ_(Mg/Mg)=1;Δρ'值的增大,说明合金元素Zr的加入提高了基体界面的应力,使该处的位错密度增加,因此界面和基体被强化了;而σ值的增多,表明Zr的溶入促使合金固溶体中含Zr晶胞界面上的电子密度连续性增强,导致错位的运动能力增强,使合金的塑性提高,降低了应力腐蚀敏感性。合金元素Zr使Mg-Zr合金固溶体的n'A值增大,Δρ'值提高,σ值上升,是固溶强化和界面强化综合作用的结果。     

稀土元素对MnS夹杂物变形能力影响的价电子理论分析

基于固体与分子经验电子理论，计算了MnS及固溶稀土元素的（Mn，RE）S的相空间价电子结构及与合金相硬度和塑性有关的价电子结构参数，即最强键上的共价电子对数和晶格电子密度。用价电子结构参数nA和ρT^L分析讨论了稀土元素使MnS抗变形能力增大的微观本质原因。发现稀土元素溶入后减小了MnS的晶格电子密度，增大了相邻密排面间最强共价键的结合能力，增大了滑移的难度，进而使MnS的抗变形能力增强，并发现随着MnS中固溶稀土量的增多，MnS的抗变形能力逐渐增强。     

Al-Ag合金η型GP区的强化作用和界面能分析

考虑温度对晶格常数的影响，运用固体与分子经验电子理论，对Al-Ag合金的Ⅵ型GP区的价电子结构进行计算；在此基础上，运用Beeker推广模型，对该体系的η型GP区与基体之间的界面能进行预测。从计算得到的各种价电子成键结果中发现，η型GP区的Ag-Ag原子之间的结合倾向最大，表明时效过程中，Ag原子容易以η型GP区的形式出现偏聚；与原合金的均相过饱和固溶体相比，η型GP区有较强的共价键络，是Al-Ag合金时效硬化的重要原因；η型GP区与基体的共格界面能较基体晶粒间的界面能低，是η型GP区形成和生长的有利条件，同时计算结果体现了温度对界面能的影响。     

新型Ag-Ti_2AlN电接触材料的电弧侵蚀行为研究

采用高能球磨和粉末冶金法制备出Ag-Ti_2AlN新型电接触材料,对该触头材料的电弧侵蚀行为及其机理进行了研究,并通过扫描电镜分析电弧侵蚀后触点的表面微观结构。结果表明,Ti_2AlN增强相在改善Ag基电接触材料的燃弧时间、燃弧能量和抗熔焊性能方面具有明显优势,Ag-Ti_2AlN触头在70 000次的通断循环测试中,其平均燃弧时间为5.61 ms,平均燃弧能量为59.8 mJ,平均熔焊力仅有15 cN。在气相电弧作用下,电触头阴极形成蚀坑中心如熔岩状和"汗滴"状微观组织,Ti_2AlN增强相颗粒通过Ti、Al熔入Ag熔池,来改善熔体的黏度,从而增强抗电弧侵蚀性能。另外,由于Al元素存在优先氧化机制,形成的Al_2O_3在汽化时吸收大量的热量,从而降低阳极增重,降低阳极凸起的高度,有效提高电接触材料的可靠性。     

锰、铌对TiAl金属间化合物的电子结构及脆性的影响

采用“固体与分子经验电子理论”计算了Mn，Nb合金化对TiAl价电子结构参数的影响，并在此基础上分析了Mn，Nb合金化对TiAl合金脆性的影响。结果表明：在TiAl晶胞中，Ti，Al原子的杂阶分别为13，4，共价电子在总价电子中所占比例为78．8％；加入Mn后，Ti，Al和Mn的杂阶分别为12，4和11，共价电子在总价电子中所占比例为73．87％，TiAl合金键合的共价成分降低，因而Mn的加入可以改善。TiAl的脆性；而Nb加入后Ti，Al和Nb的杂阶分别为12，4和7，共价电子在总价电子中所占比例为79．2％，TiAl键合的共价成分有所提高，从而Nb的加入可能进一步降低TiAl的延性。     

NiTi合金的价电子结构分析及结合能计算

应用固体与分子经验电子理论对ＮｉＴｉ合金的价电子结构进行了分析，并计算了该合金的理论晶格常数和理论结合能，计算结果与实验结果完全一致，为研究ＮｉＴｉ合金的宏观性能提供了理论参考。     

合金粉末预氧化法制备Ag-SnO2-Y2O3电接触材料的研究

Ag-SnO2是各国电接触材料研究人员近年来新开发的一种无镉新型触头材料,它具有较好的导电导热性,优良的耐热性、抗电弧烧蚀性和抗熔焊性,是目前代替Ag-CdO的最理想材料。本文通过合金粉末预氧化法、复合粉体改性处理技术来制备Ag-SnO2-Y2O3电接触材料,添加稀土后合金粉末容易氧化,氧化粉体经改性处理后可有效改善氧化物颗粒与银基体间的润湿性、改善材料的后续加工性能,并且所制备的Ag-SnO2-Y2O3材料密度高、组织均匀、不存在宏观偏析,SnO2和Y2O3颗粒在材料中弥散均匀分布。     

Al-Mg-Sc合金的原子键强与力学性能

运用固体经验电子理论(EET)，对掺微量Sc的Al—Mg合金的价电子结构进行计算。结果表明：在合金熔体中Sc与Al原子存在强的结合倾向，易形成粗大的Al3Sc颗粒，起非匀质形核细化晶粒作用；在合金凝固过程中，形成Al—Sc偏聚区，析出细小弥散的Al3Sc颗粒，增强了合金基体和晶界的共价键络，使合金的硬度、强度和晶粒热稳定性都得到提高。     

Calculation and Analysis of Valence Electron Structure of Mo2C and V4C3 in Hot Working Die Steel

Taking the hot working die steel （HWDS） 4Cr3Mo2NbVNi as an example, the phase electron structures （PES） and the biphase interface electron structures （BIES） of Mo2C and V4 C3 , which are two kinds of important carbides precipitated during tempering in steel were calculated, on the basis of the empirical electron theory of solids and molecules and the improved TFD theory. The influence of Mo2 C and V4 C3 on the mechanical properties of HWDS has been analyzed at electron structure level, and the fundamental reason that the characteristic of the PES and the BIES of carbides decides the behavior of them has been revealed.     

Multiphase diffusion in Ag-Zn alloys

Multiphase diffusion was studied in Ag-Zn alloys at 600°C with vapor-solid diffusion couples. The experiments were performed with a β(bcc) alloy as vapor-source material and with diffusion disks (fcc) of either pure silver or an α alloy. The diffused couples were studied metallo-graphically and by electron microprobe analysis. Interdiffusion coefficients for each of the phases were calculated from data on the expansion of the couple and the motion of the α/β interface on the basis of new relations developed from an analysis of two-phase vapor-solid couples. Also, the compositions at the α/β interface differed little from those determined from an equilibrated two-phase alloy.     

Out-diffusion of the noble component during the initial stage of the oxidation of γ′-Ni3Al

Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies of the oxidation behaviour of single crystalline γ′-Ni₃Al revealed that Ni diffuses through the oxide layer to the surface of the material during oxidation at low oxygen partial pressure. Small pure nickel particles (diameter ∼ 50 nm) form on top of the oxide scale. In this paper, this observation is explained on the basis of a micromechanical model. The model assumes that at intermediate temperatures the prevailing transport mechanism is the diffusion along the oxide/metal interface caused by compressive stresses generated during oxide growth. Relaxation of internal stresses as well as the formation of the small Ni-particles on top of the oxide surface are controlled by interface diffusivity. Other possible stress relief mechanisms can be excluded by theoretical estimates.     

Al-Er二元合金的价电子结构与固溶度研究

利用固体与分子经验电子理论(EET),计算分析了Al-Er合金的价电子结构。计算了不同温度下Er在基体铝中的平衡固溶度,同时结合界面前的溶质原子再分配原理,研究了在凝固过程中溶质原子Er的分配问题。结果表明:在Al3Er晶胞中最强Al-Er共价键的共价电子数为0.35798,表明Al-Er之间存在强烈的相互作用,在合金凝固过程中存在较大的形成金属间化合物Al3Er的趋势。固溶体中3种晶胞中最强键键能的关系为:EErEAl-ErEAl。因此Er元素的加入可以提高Al基体的结合强度,从而提高合金的抗高温性能。Er在基体铝中平衡固溶度很低,共晶温度928K下铒的固溶度仅为0.017%,平衡分配系数K约为0.00281,运用sheil模型计算表明当铒含量很低的情况下,凝固过程溶体中也会存在较大的成分过冷,随着凝固过程的进行,固液界面铒原子偏聚与铝结合生成Al3Er,起到异质形核的作用,细化了铸态晶粒组织。     

应用BP网络建立新型高强韧钢的结构形成因子与抗拉强度的关系

根据固体与分子经验电子理论计算了19组新型高强韧钢的试验数据所对应的结构形成因子S值,从中随机抽取16组数据,应用人工神经网络的BP结构进行训练,用其余3组数据进行检验,其平均训练误差为0．8731％,平均检验误差为0．9657％,建立了价电子结构与强度这间的定量关系,为从电子层次进行合金成分设计进行了有益的尝试。     

Effects of Additives and Impurity on the Adhesive Behavior of the NiAl(110)/Al2O3 (0001) Interface: An Ab Initio Study

Using ab initio density functional theory (DFT), the adhesive behavior of NiAl(110)/Al₂O₃(0001) interface in thermal barrier coatings was systematically studied with an emphasis on the effects of alloying additives and impurity elements. To reveal possible atomic-scale mechanisms, the separations between certain atoms at the interface, the electron localization function (ELF), and the electron density of states (DOS) are thoroughly investigated. First, effects of individual elements such as S, Pt, and Cr, and reactive elements (REs) Hf, Zr, and Y, on the work of separation, W _sep, of the interface were examined. As expected, the segregation of S to the interface significantly degrades the adhesion, while the substitution of Pt for Ni adjacent to the interface does not enhance the W _sep. Cr and RE addition to the interface individually result in a considerable increase of W _sep. Second, the addition of Pt, Hf, and Cr to the S containing interface is shown to mitigate the detrimental effect of sulfur to some extent. Co doping the interface with a selected combination of (Pt, Hf), (Pt, Cr), (Cr, Hf), (Cr, Y), (Hf, Y), and (Y, Zr) was implemented to probe possible synergistic interactions between elements on W _sep. Synergistic effects are detected on increasing W _sep for (Hf, Y), (Hf, Zr) combinations. Co doping the interface with (Cr, Y) and (Cr, Hf), however, is found to weaken the adhesion. Through a detailed analysis of electronic structures in terms of ELF and DOS, four dominant bonds across the interface, RE-O, RE-Ni, Al_oxide-Ni, and Al_NiAl-O, are identified to play a decisive role in governing the adhesive strength of the interface.     

623K温度下SnxZn1-x/Ni扩散偶的界面反应

为研究Sn-Zn合金(无铅焊料的候选者)和Ni基体(Cu基上的扩散阻挡层)的界面反应,制备一系列原子分数x分别为14.8％、22％和31％的液固扩散偶Sn1-xZnx/Ni;在623 K温度下恒温退火后,用扫描电镜和电子探针检测与分析扩散偶的界面结构,研究退火时间和合金中的Zn含量对扩散层结构和形貌的影响.结果表明,S...     

Multiperspective Approach to Exploring Comprehensive Cause Factors for Interface Issues

The severity of interface issues and the necessity of interface management (IM) have not received adequate recognition from both industry and academia. The understanding of interface issues is still insufficient and the proposed or employed measures are unilateral, which result in unsatisfactory IM performance in construction projects. After establishing IM’s importance in the construction industry, this paper presents a multiperspective approach that systematically explores comprehensive cause factors for various interface issues. From six interrelated perspectives, namely people/participants, methods/processes, resources, documentation, project management, and environment, hierarchical cause factors are identified and presented in a structured way. These cause factors are further converted into a series of interface management and control elements that allow for the development of an object data model and a systematic model-based IM strategy dealing with all interface issues. The multiperspective approach outperforms other research methods that analyze selected interface issues in a loose and isolated way. The findings contribute a holistic view of what causes interface issues as well as provide a solid theoretical basis for practitioners and researchers to seek all-around IM solutions.