La在A1_2O_(3(sf))/Al-5.0%Cu复合材料界面的分布及界面结构研究

挤压铸造A12O3(sf)/Al-5.0%Cu复合材料时添加适量稀土La,并研究了界面附近La元素的分布。添加稀土后能明显的改善纤维与基体的润湿性,并促进了界面反应的发生,在纤维与基体合金之间生成致密的厚度约2μm的过渡层,并建立了界面的生成及结构模型。     

稀土La对Al-Si合金复合材料凝固组织与溶质偏析的影响

利用挤压铸造法制备了Al2O3/Al-Si-La复合材料;研究了稀土La对复合材料凝固组织以及基体合金凝固时溶质偏析的影响。结果表明,稀土La可细化基体合金的凝固组织,La富集在界面附近,有利于改善铝合金液对氧化铝短纤维的润湿性,但是未发现任何富稀土相在界面上形成。稀土La对基体合金中镁的偏聚没有明显的影响,镁和稀土La均在界面处富集,且它们的分布位置大致近似。     

La2O3对钢基陶瓷涂层组织与性能的影响

采用热化学反应法在中碳钢(45钢)基体上,以稀土氧化镧(La2O3)为添加剂,制备A12O3陶瓷涂层,并对其组织和性能进行测试和分析.结果表明:稀土氧化镧(La2O3)可以改善陶瓷涂层的组织及性能,陶瓷涂层的硬度和耐蚀性明显提高;添加了稀土氧化镧(La2O3)的A12O3陶瓷涂层,在900℃固化时有MgFeZr3O4、MgSiO3等新相生成;当陶瓷涂层中稀土添加剂(La2O3)含量约为1.19％时,涂层组织更加致密,涂层与基体的冶金结合更加明显,涂层耐蚀性能更好.     

La对Al2O3f/Al-Mg复合材料凝固溶质偏析的影响

利用挤压铸造法制备了Al2O3／Al-Mg-La复合材料。研究了La在铝合金基体中的分布，并探讨了La对基体凝固时溶质元素偏析的影响。结果表明，La富集在界面附近，有利于改善铝合金液对Al2O3f的润湿性，但是在界面上未发现任何富稀土相的形成。La的加入对基体合金中的Mg的偏聚没有很明显的影响，Mg和La作为表面活性元素都在界面处富集，且它们的分布位置大致一样。     

Al2O3短纤维增强Al-5Cu-0.6La合金的元素分布及其溶质偏析研究

采用挤压铸造法制备了Al2O3r/Al-5Cu-0.6La复合材料,研究了其凝固组织及其溶质在纤维附近的分布.结果表明:Al2O3纤维与基体间润湿良好,生成了致密的界面层;在凝固过程中,α-Al相在短纤维间隙中形核并向纤维表面生长,纤维表面Cu和La元素的浓度增大,纤维间隙中的Cu元素的浓度减小.La的加入改变了凝固过程中的溶质传质参数,根据Clyne-Kurz公式的计算和统计物理的分析,将会生成更多的共晶组织.     

稀土镧对Sn3．5Ag0．5Cu钎料组织性能的影响

运用莱卡显微镜、显微硬度计、拉伸试验机等仪器设备,研究添加不同含量稀土元素La对Sn3．5Ag0．5Cu钎料及其与Cu基体焊合后微观组织及性能影响。结果表明：添加不同含量的稀土La均能使Sn3．5Ag0．5Cu钎料及其与Cu基体焊合后组织与性能得到改善,其中以La含量达到0．05％时为最优,显微硬度及剪切强度分别提高14％和10．7％;基于热力学理论计算结果表明稀土元素La具有“亲Sn”倾向,可减小钎料中锡基化合物界面锡的活度,降低IMC的长大驱动力。     

添加La2O3对激光烧结(WC-Co)p/Cu金属基复合材料组织和成形性能的影响

研究了稀土氧化物La2O3添加量对激光烧结直接成形(WC-10Co)颗粒增强Cu基复合材料的影响.结果表明,优化La2O3含量(1.0%),可细化激光烧结组织,提高增强颗粒分散均匀性以及颗粒/基体界面结合性能,成形致密度高达理论密度的96.3%,显微硬度HV可达403.1;而过量添加La2O3(≥1.5%),导致激光成形性能降低.讨论了稀土原子对颗粒增强金属基复合材料激光烧结成形的作用机理.     

稀土对AZ91镁合金干湿交替循环腐蚀行为的影响

镧铈(La,Ce)混合稀土的添加改变了AZ91镁合金微观组织和元素分布。La元素与Ce元素在AZ91镁合金中以不同的形式存在,一部分固溶在镁合金基体中,一部分参与生成了针状的Al4(La,Ce)相和粒状的Al_(10)Ce_2Mn_7相。稀土添加后AZ91镁合金中β相的体积分数有所降低,Al元素分布由晶界向晶内迁移。对不同添加量的稀土镁合金在模拟融雪剂溶液中的干湿交替循环腐蚀行为的研究结果表明,La、Ce混合稀土的添加,可以增加镁合金表面膜的致密度。虽然混合稀土降低了镁合金的自腐蚀电位,但腐蚀电流密度相比较于AZ91明显降低。SECM结果则表明,稀土添加可以减少镁合金表面微区的活性点数量。     

熔炼时间对稀土单晶合金坩埚界面反应的影响

为了实现稀土单晶高温合金中稀土含量的稳定控制,明确稀土元素在熔炼过程中参与的坩埚界面反应机理,研究了熔炼时间对含Y高温合金CMSX-4与Al2O3陶瓷坩埚在真空感应熔炼过程中的界面反应和稀土Y收得率的影响。实验结果表明：随着熔炼时间的延长界面反应加剧,熔炼过程中Y首先与Al2O3陶瓷基体发生反应生成Y2O3,生成的Y2O3会继续与Al2O3发生反应生成Y、Al原子比不同的铝酸钇反应层,最终坩埚表面形成的界面反应产物由外层的YAlO3、内层的Y3Al5O12(Y3Al2(AlO4)3) 以及附着的高温合金组成。熔炼10~30min时合金中稀土Y收得量为41.023、4.566和5.368ppm。     

La对氟盐法制备Al-Ti-B-La反应机理及其细化效果的影响

利用氟盐法制备Al-5Ti-1B和Al-5Ti-1B-1La中间合金,对比分析稀土La添加对合成反应速率、第二相粒子的形态及物相组成的影响,并对比研究中间合金对纯铝和Al-8Si合金的细化效果。结果表明:添加稀土La元素会加速氟盐反应的进行,有利于Ti、B元素的吸收;稀土La可以有效地细化Al_3Ti相,并与其反应生成细小弥散分布的Al_(20)Ti_2La相,同时减弱TiB2相聚集成团的倾向,在细化纯铝过程中表现出更优异的细化长效性;在细化Al-8Si合金过程中,Al-5Ti-1B-La中间合金中所存在的大量细小弥散的第二相形核粒子可以有效地细化铝基体,同时Al_(20)Ti_2La相熔解所释放的稀土La原子还可以对硅相产生变质细化作用,表现出较强的细化效果。     

Size-dependent interface energy and related interface stress

General equations for the size-dependence of solid–liquid interface energy, grain boundary energy and the intrinsic interface stress without free parameters are derived. The predicted results correspond to computer simulation results, the first principles calculation, the modified embedded-atom-method potential results and experimental results. In addition, the possible physical background of positive or negative interface stress is analyzed.     

Thermal interface materials

Thermal interface mateials for facilitating heat transfer by conduction across two adjacent surfaces are reviewed. They include thermal fluids and pastes, solders, phase change materials (PCMs), and resilient thermal conductors.     

Surface state density at the semiconductor-glass interface

An investigative technique for the determination of the surface state density (SSD) at the semiconductor-lead-borosilicate-glass interface is proposed. It is shown that this technique involving differentiation of the C-V dependence is a more precise and less labor-consuming method, which shows the uniqueness of the solution.     

Properties and determination of the interface stiffness

The chemical potential of a curved interface contains a term that is proportional to the product of the interface curvature and the interface stiffness. In crystalline materials, the interface stiffness is a tensor. This paper examines several basic issues related to the properties of the interface stiffness, especially the determination of the interface stiffness in particular directions (i.e. the commonly used scalar form of the interface stiffness). Of the five parameters that describe an arbitrary grain boundary, only those describing the inclination are crucial for the scalar stiffness. We also examine the influence of crystal symmetry on the stiffness tensor for both free surfaces and grain boundaries. This results in substantial simplifications for cases in which interfaces possess mirror or rotational symmetries. An efficient method for determining the interface stiffness tensor using atomistic simulations is proposed.     

Characterizing the interface of nickel-zincate-aluminum thin films

The manufacture of plated computer memory disks requires a complex sequence of processing steps. One of the most important factors affecting disk surface topography and adhesion between nickel and aluminum was found to be the formation and diffusion of a zincate thin film at the nickel-aluminum interface. To improve the adhesion, the strength of the weak link (the zinc layer) must be increased. This can be accomplished by alloying the zinc layer with the aluminum and nickel layers by co-diffusion, which is accelerated at high temperatures, or by keeping the zinc layer very thin. Surface topography can be modified by changing the metallurgical properties of the substrate, promoting the diffusion of elements between layers at elevated temperatures, or adjusting the zincating bath parameters.

     

Parabolic vs linear interface shift on the nanoscale

It was shown very recently that diffusion nonlinearity, caused by the strong composition dependence of diffusion coefficients, can lead to surprising effects on the nanoscale: a nonparabolic shift of interfaces (both in ideal and phase separating systems) and sharpening of an initially diffuse interface in ideal systems. Some of these can not be interpreted even qualitatively from Fick’s classic equations. For instance, the nonparabolic shift of an interface at the very beginning is a consequence of the violation of Fick’s first equation on the nanoscale, and the transition from this to the classic parabolic behavior depends on the strength of the nonlinearity and the value of the solid solution parameter V (proportional to the heat of mixing). Experimental and theoretical efforts to explore the above phenomena are summarized in this paper.     

Charge transfer at the antiscale composite layer-electrolyte interface

Properties of composite coatings based on oxide layers formed on a titanium surface using the plasmic electrolytic oxidation method and processed using Forum? superdispersed polytetrafluorinethylene were investigated. A combination of electrochemical impedance spectroscopy, differential thermal analysis, and thermal gravimetry methods allowed one to establish the change of the surface state as a result of heating that determines the charge transfer mechanism at the heterostructure-electrolyte phase interface and the difference in the thermodynamic stability of the temperature fractions of the employed polymer. Original Russian Text ? S.V. Gnedenkov, S.L. Sinebryukhov, D.V. Mashtalyar, V.S. Egorkin, A.K. Tsvetnikov, A.N. Minaev, 2007, published in Korroziya: Materialy, Zashchita, 2006, No. 5, pp. 27–33.     

Inhomogeneities of the interface produced by explosive welding

Results of studying structure of the transition zone for a number of joints produced by explosive welding are presented. The joints of dissimilar metals (titanium-orthorhombic titanium aluminide, coppertantalum, and others) have been investigated. The welded pairs of metals differ from each other in mutual solubility; moreover, some pairs (copper-tantalum) virtually lack it. The interface was found to be uneven; it contains inhomogeneities, irrespective of whether it is flat or wavy. It is shown that the formation of interfacial protrusions determines the adhesion of materials. A granulating fragmentation has been found near the protrusions. The role of various processes in explosive welding has been discussed. The formation of protrusions does not depend on whether the metals of a pair have mutual solubility or not. However, this factor affects the structure of zones of local melting. The metals that have mutual solubility form true solutions; in the absence of solubility, these zones represent colloidal solutions. It is shown that sometimes the local melting zones do not present a real danger for the strength of the joint. A hypothesis is proposed that the formation of a wavy surface is possible through the self-organization of the previously formed protrusions.