Fe73.5Cu1Nb3Si13.5B9非晶合金的激波纳米晶化速率和晶化度的对比研究

对Fe73.5Cu1Nb3Si13.5B9等非晶合金进行了退火和激波诱导两种方式的晶化实验以及XRD和DSC分析.着重对合金的晶化速率和晶化度等特性展开了研究和讨论.进一步证实了激波纳米晶化是一种包含着新机理的寓意丰富的晶化现象.也再次验证了作者曾经提出过的"激波流化相变"模型的合理性.     

Fe基纳米晶合金的晶化机理研究

根据用原子力显微镜对在不同温度下晶化的Fe基非晶合金薄带三维介观结构的观察,结合X射线衍射、Mssbauer谱等前人已有的实验结果并在目前已有的理论研究基础上,对Fe基非晶合金薄带在不同温度下的晶化过程进行了系统的分析、研究,提出了两种Nb-B框架介观结构、团聚相和单位体积纳米晶粒平均数等新概念,建立了Fe基纳米晶合金的晶化机理假说,提出了描述Fe基非晶合金晶化过程的介观织构模型.这个模型能够演化成二相结构模型和三相互套结构模型,还可以合理地解释现有的实验结果以及500—600℃退火中Fe基纳米晶巨磁阻 关键词： Fe基纳米晶合金 晶化机理 两种Nb-B框架介观结构 团聚相     

非晶Ti3Al合金的变形晶化机理的原子模拟

利用分子动力学方法研究了非晶Ti₃Al合金拉伸过程中的晶化行为，模拟结果表明局部塑性变形导致非晶合金晶化.从微观结构演化的角度分析了拉伸过程中的晶化机理，局部剪切导致拉伸过程中晶粒发生成核与合并，最终生成的晶粒具有面心立方结构.晶核的生长过程伴随着应力强化现象，非晶相中的纳米晶粒能提高非晶合金材料的强度. 关键词： 非晶合金 变形晶化 分子动力学     

Fe73.5Cu1Nb3B9Si13.5非晶态合金的激波纳米晶化研究

实验表明,非晶态合金在激波影响下会转变为纳米晶.最近的实验进一步发现,Fe_73.5Cu₁Nb₃B₉Si_13.5非晶态合金中的Cu,Nb在激波晶化中的细化作用被抑制,且样品在这种转变之后作进一步的退火处理,其晶粒度变大而晶格常数变小.在激波晶化机理分析中提出了“激波流体晶化”构想. 关键词：     

几种铁基非晶合金激波诱导晶化中的若干奇异物理效应研究

应用x射线衍射、透射电子显微镜和差示扫描量热实验技术，研究了FeCuNbBSi，FeBSi，FeMoBSi几种铁基非晶合金的激波诱导晶化.研究结果表明：非晶态合金激波诱导晶化中存在若干应用传统长程扩散相变理论难以解释的奇异物理效应.用非晶态合金激波流化晶化可以很好地解释激波诱导非晶晶化中的各种奇异物理效应. 关键词： 激波晶化 非晶态合金 激波流化 流体扩散     

FeCuNbBSi等多中Fe基非晶态合金激波晶化的DSC研究

应用升温、等温和重复加热的DSC技术，对几种非晶合金的激波晶化和退化晶化作了对比研究，结果表明，尽管激波晶化时间极短，仅为退火晶化时间为10^-6－－10^-8，但晶化度却极高，接近100％。激波晶化形成多种成分和结构的结晶相，形式上很像扩散性相变，然而其相变速率却是退火转变的千万倍，而且生成相十分稳定，这一现象用传统的固态扩散相变理论很难解释，激波晶化是一种新的晶化形式，是一种新的纳米合成技术。     

Fe78B13Si9、(Fe0.99Mo0.01)78B13Si9非晶合金的激波晶化实验研究

 研究了Fe₇₈B₁₃Si₉、(Fe_0.99Mo_0.01)₇₈B₁₃Si₉非晶合金的激波晶化行为。激波是由氢-氧爆炸产生的。实验结果表明：激波能使非晶合金在微秒时间内晶化,晶化主相为α-Fe基固溶体,次晶化相为Fe₃Si,且观察到α-Fe基因溶体晶格常数变小。用DTA分析进一步证实：激波晶化是比较完全的,晶化相相当稳定。     

FeCuNbBSi等多种Fe基非晶态合金激波晶化的DSC研究

 应用升温、等温和重复加热的DSC技术，对几种非晶合金的激波晶化和退火晶化作了对比研究。结果表明，尽管激波晶化时间极短，仅为退火晶化时间的10^-6～10^-8，但晶化度却极高，接近100%。激波晶化形成多种成分和结构的结晶相，形式上很像扩散性相变，然而其相变速率却是退火转变的千万倍，而且生成相十分稳定，这一现象用传统的固态扩散相变理论很难解释。激波晶化是一种新的晶化形式，是一种新的纳米合成技术。     

非晶Ni88P12合金薄膜的表面形貌特征与晶化行为的研究

采用化学镀的方法在363K和p型Si（100）衬底上制得非晶Ni₈₈P₁₂合金薄膜．利用X射线衍射、X射线光电子能谱、扫描隧道显微镜和原子力显微镜对非晶合金薄膜及其经处理后形成的氧化态、还原态和晶态的结构、组分和表面的形貌特征作了研究，并对它的晶化行为作了初步探讨．结果表明，非晶合金薄膜是由纳米级微粒聚集成微米级颗粒组成；在低于晶化温度条件下经氧化和还原处理后的薄膜表面晶化；在晶化过程中，合金薄膜的非晶纳米微粒转变为微晶后长大成晶粒，其表面结构光滑平坦，几何边界 关键词：     

Al-Ni-RE非晶合金的晶化行为和热稳定性

本文制备了一系列Al-Ni-RE (RE=La, Ce, Y) 非晶合金薄带, 利用差示量热扫描仪和X射线衍射仪考察了非晶合金的晶化行为和初生相, 并分析了其与合金成分和原子特性间的关系. 结果表明: 在拓扑不稳定参数λ以有效原子半径修正为λ'后, 每一Al-Ni-RE非晶合金体系可由其两个临界值划分为纳米晶、纳米玻璃和玻璃三类; Al-Ni-RE非晶合金的晶化开始温度和混合焓与λ'成良好的线性关系, 即λ'能很好的表征Al基非晶合金的热稳定性. 关键词： Al基非晶 玻璃转变 初生相 热稳定性     

非晶合金Fe73.5Cu1Nb3Si13.5B9的激波晶化及其特征

 研究了非晶合金Fe_73.5Cu₁Nb₃Si_13.5B₉（FINEMET）的激波晶化。与退火晶化比较,激波晶化具有一系列鲜明特征,这些特征是固态下扩散性相变理论难以解释的,有深刻的物理内涵。     

Self-propagating crystallization waves in the TiCu amorphous alloy

Self-propagating crystallization waves are detected and experimentally demonstrated in the Ti₅₀Cu₅₀ amorphous alloy obtained by the melt spinning (ultrafast quenching) method. High-speed thermographic recording has shown that crystallization waves can appear spontaneously at the heating of an amorphous strip to 300–350°С or at the local initiation by a hot tungsten coil of a small segment of the strip preliminarily heated to 230–250°С. In the former case, the crystallization wave propagates at a velocity of ~7 cm/s; in the latter case, the crystallization wave propagates in a self-oscillation mode at an average velocity of ~1.2 cm/s. The temperature gradient across the wavefront is about 150°С. The samples crystallized in the self-oscillation mode have a characteristic banded structure with a smaller grain in depression regions. The crystallization product in all samples is the TiCu tetragonal intermetallic phase.     

Mg-Ni-Nd非晶合金晶化温度与晶化驱动力的预测

通过对Buschow提出的预测二元非晶态合金晶化温度的“最小空位”模型进行扩展,并进一步结合Miedema理论得到了一种预测三元非晶态合金晶化温度和晶化驱动力的理论方法.利用该方法计算了(Mg_70.6Ni_29.4)_1-xNd_{x(x＝5,10,15)非晶态合金的晶化温度、晶化驱动力以及晶化焓.其中晶化温度和晶化焓的理论预测值与实验值的相对误差分别小于8%和7%.同时发现较高的晶化驱动力会降低 关键词： 非晶态合金 晶化温度 晶化驱动力}     

Stability of (Fe-Tm-B) amorphous alloys: relaxation and crystallization phenomena

Fe-Tm-B base (TM=transition metal) amorphous alloys (metallic glasses) are thermodynamically metastable. This limits their use as otherwise favourable materials, e.g. magnetically soft, corrosion resistant and mechanically firm. By analogy of the mechanical strain-stress dependence, at a certain degree of thermal activation the amorphous structure reaches its limiting state where it changes its character and physical properties. Relaxation and early crystallization processes in amorphous alloys, starting already around 100°C, are reviewed involving subsequently stress relief, free volume shrinking, topological and chemical ordering, pre-crystallization phenomena up to partial (primary) crystallization. Two diametrically different examples are demonstrated from among the soft magnetic materials: relaxation and early crystallization processes in the Fe-Co-B metallic glasses and controlled crystallization of amorphous ribbons yielding rather modern nanocrystalline Finemet alloys where late relaxation and pre-crystallization phenomena overlap when forming extremely dispersive and fine-grained nanocrystals-in-amorphous-sauce structure. Mössbauer spectroscopy seems to be unique for magnetic and phase analysis of such complicated systems.     

Ab Initio computer simulation of the early stages of crystallization: application to Ge(2)Sb(2)Te(5) phase-change materials

By virtue of the ultrashort phase-transition time of phase-change memory materials, e.g., Ge(2)Sb(2)Te(5), we successfully reproduce the early stages of crystallization in such a material using ab initio molecular-dynamics simulations. A stochastic distribution in the crystallization onset time is found, as generally assumed in classical nucleation theory. The critical crystal nucleus is estimated to comprise 5-10 (Ge,Sb)(4)Te(4) cubes. Simulated growth rates of crystalline clusters in amorphous Ge(2)Sb(2)Te(5) are consistent with extrapolated experimental measurements. The formation of ordered planar structures in the amorphous phase plays a critical role in lowering the interfacial energy between crystalline clusters and the amorphous phase, which explains why Ge-Sb-Te materials exhibit ultrafast crystallization.     

Photoemission (UPS and XPS) study of crystallization of amorphous GeTe film

In situ photoemission (UPS and XPS) measurements have been performed for amorphous GeTe films. The photoemission spectra exhibit a drastic change upon thermal annealing and/or the crystallization of the film. It has been found that an amorphous GeTe film deposited onto a room temperature substrate has a 4-2 coordinated local structure, while a highly disordered amorphous GeTe film evaporated onto a cooled (77 K) substrate is largely 3-3 coordinated, and relaxes into the 4-2 coordinated structure upon thermal annealing within amorphous phase.     

Inherent submicroporosity and crystallization of amorphous alloys

The effect of inherent submicroporosity (regions with an excess free volume) in amorphous alloys on the regularities of their crystallization is investigated. Inherent submicroporosity arises in amorphous alloys prepared by quenching under different conditions. It is proved that this effect should be taken into account in the first stage of crystallization of amorphous alloys.