共查询到19条相似文献,搜索用时 609 毫秒
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运用实空间递归方法研究了添加元素Nb,Ta,Y,La对Zr基非晶合金的非晶形成能力和耐腐蚀性能的影响.用计算机编程构造了Zr基非晶中初始晶化相Zr2Ni的原子结构模型,用Zr2Ni中的二十面体原子团簇模拟非晶中的二十面体团簇.计算了替代二十面体中心或顶角位置原子前后Ni,Zr及合金元素的局域态密度、团簇中心Ni与近邻Zr原子及Ni与替代元素Nb,Ta,Y,La间的键级积分,还计算了合金元素替代前后团簇的费米能级.局域态密度计算结果表明:合金元素Cu占据二十面体团
关键词:
电子结构
Zr基大块非晶
非晶形成能力
耐蚀性 相似文献
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通过固相反应将晶态的金属转变为非晶态合金是近年来人们发现的一种新的制备北晶态合金的方法,这种方法原则上完全不受以往限制人们获得大块非晶态合金的因素的约束,因而给我们开发适合于大规模工业应用的非晶态合金生产工艺开辟了新的途径.目前,人们对固相反应非晶化机理的研究可以分为两个方面,一是固相反应的反应驱动力;二是固相反应的动力学过程.本文着重就金属多层膜间固相反应非晶化机理的实验和理论研究作了一些介绍. 相似文献
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利用透射电镜研究了Zr65Al7.5Ni10Cu12.5Ag5非晶合金的Vickers压痕内微观结构的变化. 结果发现,压痕塑性变形诱导非晶合金发生了晶化,在压头棱角下面的区域内有尺寸大于1 μm的晶体析出. 选区电子衍射分析表明,该析出相是稳定的CuZr2或NiZr2四方晶体,而没有析出该非晶合金在加热过程中的初生相二十面体准晶相,说明非晶合金的机械稳定性与热稳定性是有区别的. 打压痕过程中的温度升高是可以忽略的,本工作进一步证实了塑性变形诱导非晶合金晶化的主要动力是粘性流动而非局部热效应.
关键词:
非晶合金
塑性变形
粘性流动
局部热效应 相似文献
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通过在真空电弧熔炼炉内对合金铸锭进行反复熔炼处理,获得到了凝固组织不同的Zr65Al7.5Cu12.5Ni10Ag5合金铸锭.在相同的制备条件下,由凝固组织不同的合金铸锭通过吸铸法制备得到了薄片非晶合金.利用差示扫描量热法(DSC)对非晶合金的晶化动力学进行了分析.x射线衍射谱表明,在Zr65Al7.5Cu12.5Ni10Ag5非晶合金晶化过程中,二十面体准晶相(I相)作为初生相析出.Kissinger分析结果表明,合金铸锭的凝固组织细化,相对应的非晶合金发生晶化时,I相形成与分解的有效激活能都增大,说明非晶合金及析出的I相的热稳定性都提高.从结构的遗传性角度就合金铸锭凝固组织对相应非晶合金晶化过程中二十面体准晶相的形成动力学的影响进行了讨论.
关键词:
二十面体准晶相
晶化动力学
凝固组织 相似文献
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用掠入射X射线衍射及X射线反射对磁控溅射制取的等原子比Ni/Ti周期性多层膜晶化热处理 后的TiNi形状记忆薄膜室温微结构进行了研究.TiNi形状记忆薄膜在深度方向的相分布和元 素分布是不均匀的,都是一种多层结构.室温下其微结构特征为最外层是Ti氧化膜,再下层 是Ti3Ni4,B19’马氏体相和少量的B2奥氏体相的三相混合物,靠近 基体为主要相成分马氏体,最后是Ni和Si界面反应层.X射线反射率的拟和结果显示薄膜微结 构的分析是合理的.薄膜中相深度分布的不均匀性主要是动力学因素决定的.
关键词:
相深度分布
形状记忆
TiNi
多层膜 相似文献
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G. Principi A. Gupta R. Gupta C. Tosello L. M. Gratton A. Maddalena S. Lo Russo 《Hyperfine Interactions》1992,69(1-4):627-630
Solid state reaction in Fe?Si multilayers occuring at 300°C and 385°C has been studied using Mössbauer spectroscopy and RBS measurements. Annealing at 300°C results in partial amorphization of the system, while annealing at 385°C results in formation of crystalline phases. Possible mechanism for amorphization has been discussed. 相似文献
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The amorphization of Fe−Zr multilayers due to ion-beam mixing and solid state reaction is studied in detail using the CEMS
and CXMS. The nature of the amorphous Fe−Zr phase produced by both processes is the same suggesting that diffusion of Fe is
an important mechanism during ion-beam mixing. 相似文献
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Q. Zhang W.S. Lai G.W. Yang B.X. Liu 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):223-231
An embedded-atom potential for the Ni-Nb system is constructed using physical properties obtained from first-principle calculations.
Employing the potential, molecular-dynamics simulations are performed to study the interfacial reaction in Ni/Nb multilayers
upon annealing at medium temperatures. The results show that a preset disordered interlayer, which is obtained by exchanging
Ni and Nb atoms in the interfaces, may act as a nucleus of amorphous phase and is usually necessary for amorphization. It
is found that the growth of the amorphous interlayer is in a planar mode and exhibits an asymmetric behavior due to a faster
consumption of Ni than that of the Nb layer; this is also indeed observed experimentally. Moreover, performing a simulation
with solid solution models, it is found that the Nb lattice can accommodate a large number of Ni atoms and still retain a
crystalline structure, while a small amount of Nb atoms induce a spontaneous decay of the Ni lattice. Such differences in
solid solubility is thought to be the physical origin of the asymmetric growth observed in experiments and simulations.
Received 7 June 1999 and Received in final form 12 January 2000 相似文献
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We report on the fabrication of Ni/Al2O3/Si and textured Ni/Al2O3/Si3N4 multilayers containing Ni nanoparticles that exhibit significantly improved results. The secondary phases arising from thermal reaction between Ni and Si can be remarkably suppressed with increasing layers of Al2O3 and deposition of Ni/Al2O3 multilayers on Si3N4 substrates. Atomic force microscopy shows the formation of large as well as nanoclusters of Ni when grown on Si, whereas textured Ni nanoparticles are formed on Si3N4 substrates. The magnetization measurements on Ni/Al2O3/Si containing a single buffer layer of Al2O3 shows higher coercivity field with magnetic nanowire-like behavior, whereas with several Al2O3 alternate layers almost a superparamagnetic-like behavior is observed. However, significantly improved magnetic hysteresis was observed in textured Ni/Al2O3/Si3N4 multilayers due to preferred alignment of Ni nanocrystallites. 相似文献
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J. J. Suñol 《哲学杂志》2013,93(20):2323-2342
Progress in the ball milling amorphization of elemental powders with the overall composition Fe40Ni40P20 ? xSix (X = 6, 10 and 14) and thermally induced crystallization of obtained alloys were characterized by differential scanning calorimetry, X-ray diffraction and transmission Mössbauer spectroscopy (TMS). Diffusion of Si into Fe and Ni alloys promotes the formation of the amorphous phase, via previous formation of (Fe, Ni) phosphides. After milling for 32–64 h, most of the powders are amorphous but bcc Fe(Si) crystallites remain (about 5% in volume). TMS results indicate that homogenization of the amorphous phase occurs by interdiffusion of Ni and Fe in Fe(Si,P)-rich and Ni(Si,P)-rich zones respectively. Annealing induces structural relaxation of stresses induced by milling, growth of bcc Fe(Si) crystallites, precipitation of bcc Fe(Si) and fcc Ni–Fe, and minor phases of Ni-rich silicides and (Fe, Ni) phosphides. The main ferromagnetic phase is bcc Fe(Si) for Fe40Ni40P10Si10 powders obtained after milling for 32 h. However, it is fcc Fe–Ni for the same alloy after milling for 64 h. In the later powders, as well as for alloys with x = 6 and 14 milled for 32 h, the fcc Fe–Ni shows the Invar magnetic collapse. 相似文献
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In this review article, first a brief summary is presented concerning the formation of amorphous alloys (or metallic glasses) in binary metal systems by solid-state reaction of metallic multilayers. Secondly, under the framework of Miedema's model, thermodynamic modelling of crystal-to-amorphous transition is developed with special consideration of the excess interfacial free energy in metallic multilayers. Thirdly, the results of molecular dynamics simulations in some representative systems are presented, revealing the detailed kinetics of the crystal-to-amorphous transition on the atomic scale, such as the temperature/time dependence of interfacial reactions, the asymmetric growth of amorphous interlayers, and the nucleation and/or presence of growth barriers resulting from the interfacial texture. Fourthly, the critical solid solubilities of some representative systems are directly determined from the inter-atomic potentials through molecular dynamics simulations and then correlated with the metallic-glass-forming ability of the systems as well as their asymmetric growth during solid-state amorphization observed in experiments and/or simulations. 相似文献
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We have fabricated periodic multilayers that comprise either Si/Tb or SiC/Tb bilayers, designed to operate as narrowband reflective coatings near 60 nm wavelength in the extreme ultraviolet (EUV). We find peak reflectance values in excess of 20% near normal incidence. The spectral bandpass of the best Si/Tb multilayer was measured to be 6.5 nm full width at half-maximum (FWHM), while SiC/Tb multilayers have a more broad response, of order 9.4 nm FWHM. Transmission electron microscopy analysis of Si/Tb multilayers reveals polycrystalline Tb layers, amorphous Si layers, and relatively large asymmetric amorphous interlayers. Thermal annealing experiments indicate excellent stability to 100 degrees C (1 h) for Si/Tb. These new multilayer coatings have the potential for use in normal incidence instrumentation in a region of the EUV where efficient narrowband multilayers have not been available until now. In particular, reflective Si/Tb multilayers can be used for solar physics applications where the coatings can be tuned to important emission lines such as O V near 63.0 nm and Mg X near 61.0 nm. 相似文献