非晶态NbNi合金的电性和磁性

对非晶态 Nb_(100-x)Ni_x(x=65,59.8,56.4)合金电阻随温度的变化及超导转变进行了测量,结果表明:电阻温度系数随 Ni 含量 x 的变化不是单调的,而是 x=59.8的电阻温度系数最小.定性分析表明:这是由于 x=59.8时,合金中巡游电子数目相对比较多的缘故.低温超导性的测量结果表明:x=59.8和56.4的两个样品低温下还具有超导性.     

新型高温应变电阻合金

在拉伸时,金属材料的电阻将发生改变.在弹性极限内,电阻相对变化与应变的比值保持常数,该常数称为电阻应变系数.人们利用应变-电阻效应把金属丝材制成电阻应变片,作为传感器元件.它能将构件表面的应变转换成电阻的相对变化.电阻应变系数越大,传感器的灵敏度越高.电阻应变测量技术是实验应力分析的主要方法之一,它在航空、航天、原子能、化工、机械、冶金、交通等部门获得广泛应用. 应变电阻合金是制作电阻应变片的关键材料,它直接决定应变片的各项特性.700-1000℃使用的高温应变电阻合金是国际上近20年共同探索的课题,它要求抗氧化非常好,组…     

非晶态合金与氢相互作用的研究进展

非晶态合金在力学性能、耐磨耐蚀性、磁性等方面比传统晶态合金具有显著优势,是一类有优良应用前景的新型结构与功能材料.非晶态合金与氢相互作用可以产生很多有趣的物理化学现象和应用.本文从物理基础和材料应用两个方面评述非晶态合金和氢相互作用的研究进展,在物理基础研究方面,从氢在非晶态合金中的存在状态出发,讨论氢在非晶态合金中的溶解、分布、占位和扩散等相关物理问题,进而分析氢对非晶态合金的热稳定性、磁性、内耗、氢脆等的影响.在材料应用研究方面,对非晶态储氢合金、非晶态合金氢功能膜、吸氢改善非晶态合金的塑性和玻璃形成能力、氢致非晶化、利用非晶态合金制备纳米储氢材料等方面的研究进展进行评述.最后总结并展望有关非晶态合金与氢相互作用的研究和应用.     

基于缠结微结构的非晶态玻璃态高分子材料屈服行为的分子动力学研究

非晶态玻璃态高分子材料作为结构材料在工程领域应用广泛,其机械力学性能特别是屈服变形行为受到热处理、加载应变率和环境温度的影响.采用分子动力学模拟方法研究非晶态玻璃态高分子材料不同工况下的单轴拉伸变形,基于分子链缠结微结构的概念,阐明了非晶态玻璃态高分子材料屈服和应变软化过程的内在变形机制.结果表明,拓扑缠结具有较为稳定的空间结构,难以发生解缠,决定了非晶态高分子材料屈服后的软化平台.由相邻分子链的局部链段相互作用形成的次级缠结在一定外界条件下可发生破坏或重新生成,次级缠结微结构及其演化是非晶态高分子材料发生屈服及软化的内在物理原因.     

非晶态FeCrB合金在临界浓度附近的磁特性

非晶态(Fe_(1-x)Cr_x)_(84)B_(16)(x=0—0.46)合金是用单辊急冷法制备.用交流互感电桥测量低场交流磁化率X与温度的关系,得到该合金系列的磁相图.用四端引线法测量了该浓度范围内的低温电阻反常.本文对非晶态FeCrB合金中的类自旋玻璃,电阻反常和因瓦效应共存现象用合金中存在自由的Fe,Cr原子和具有反铁磁耦合的自旋团进行简要的讨论.     

尺寸效应对非晶态TM100-xMx合金结构的影响

本文通过对非晶态合金结构的计算机模拟,研究非晶态TM_100-xM_x合金在成分基本相同条件下,M原子与TM原子尺寸比的变化对合金结构的影响。为此,分别模拟了Fe₈₀P₂₀,Co₈₁P₁₉和Fe₈₀B₂₀等非晶态合金的结构,并从径向分布函数、拓扑短程序、结构的稳定性和电子迁移引起的原子尺寸变化等方面讨论了原子尺寸的变化对非晶态合金结构的 关键词：     

温度和磁场对应变片的影响

电阻应变片的电阻不但随应变变化,而且随温度和磁场变化.为了修正温度和磁场的影响,在4.25K到300K的温度范围内,试验了镍铬合金电阻应变片WK-15-250BG-350的表观应变与温度的关系,并在不同磁场下试验了温度对应变片的影响.在低温下试验了应变片的表观应变与磁场的关系(即磁阻效应).分析了不同温度下,磁场对应变片的影响.试验结果将在TESPE装置的实际应变测量中进行误差修正.     

热处理对非晶态合金Nd4Fe96-xBx磁性的影响

本文研究了用单辊急冷方法制备的非晶态合金Nd₄Fe_96-xB_x的晶化,以及热处理对其硬磁性和相组成的影响,发现非晶态合金Nd₄Fe_96-xB_x的晶化温度比相同B含量的非晶态合金Fe_100-xB_x高120—190K,X射线衍射和热磁测量表明,15≤x≤25的样品晶化相是由Nd₂Fe₁₄B(T 关键词：     

一类q-变形叠加态光场的振幅k次方压缩及高阶反聚束特性

构造了一种由q变形相干态与q变形真空态叠加而成的态,研究了它的振幅k次方压缩性质和高阶反束特性,借助数值计算方法讨论了叠加系数、变形参数对这些特性的影响。     

高阻紫外光阴极导电基底制备及性能

在MgF_2基片上,采用电子束蒸发镀膜法制备了掺锡氧化铟(ITO)导电基底,研究了充氧及退火对ITO薄膜电阻及紫外透射比的影响。并与传统的金属导电基底Au和Cr进行了性能比较。用光学显微镜、四探针测试仪、高阻计、X射线衍射仪(XRD)和分光光度计分别测试了薄膜的表面形貌、方块电阻、形态结构和190～800 nm波段范围内薄膜的透射比曲线,得到方块电阻为10~7Ω左右时薄膜在200～400 nm波段内透射比的变化范围。实验结果表明,厚度相同时,充氧会增大ITO薄膜电阻;退火则会降低薄膜电阻并提高紫外透射比,薄膜结构由非晶态变为多晶态。方块电阻同为10~7Ω时,在200～400 nm波段充氧退火后ITO薄膜的平均透射比比Au,Cr的高10%。     

Effect of annealing on the deformation and fracture of metallic glass under local loading

An investigation is undertaken into the variations observed in the cracking resistance, the plasticity, and the structure of an 82K3KhSR metallic glass upon annealing. A method of evaluating the mechanical properties and the structural state of metallic glasses is proposed. This method is based on the indentation of the metallic glass deposited onto a substrate prepared from a polyester material and a metal. The critical annealing temperature that corresponds to drastic changes in the mechanical properties of the metallic glass is determined. It is found that dependences of the cracking resistance of metallic glasses on the indenter load exhibit a linear behavior at annealing temperatures above the critical point. An exponential decrease in the cracking resistance upon indentation is observed with an increase in the annealing temperature of metallic glasses.     

Amorphous metallic plastic

We report cerium-based bulk metallic glasses with an exceptionally low glass transition temperature Tg, similar to or lower than that of many polymers. We demonstrate that, in near-boiling water, these materials can be repeatedly shaped, and can thus be regarded as metallic plastics. Their resistance to crystallization permits extended forming times above Tg and ensures an adequate lifetime at room temperature. Such materials, combining polymerlike thermoplastic behavior with the distinctive properties of metallic glasses, are highly unusual for metallic alloys and have great potential in applications and can also facilitate studies of the supercooled liquid state.     

压力下金属玻璃Fe100-xBx的电子输运性质

 在0～1.2 GPa压强范围内、54～300 K温区，研究了金属玻璃Fe_100-xB_x（x=16、18、20和22）的电阻-温度特性，对所获得的实验数据进行了方程拟合，并对所拟合的方程用推广的Ziman理论进行了讨论。     

How does the structural inhomogeneity influence the shear band behaviours of metallic glasses

ABSTRACT

Here we propose a model to understand the influence of structural inhomogeneity on the shear band behaviours of metallic glasses. By considering the inhomogeneous structure and stress concentration, the model predicts that the strain for shear band nucleation in metallic glasses can be variable and far below the theoretical elastic limit. During sliding, the shear band will approach a dynamic equilibrium state of balanced free volume generation and annihilation. By considering the accumulation of irreversible structure change, the shear band will finally develop into fracture. Under fluctuating load, the shear band shows an ‘activate-arrest’ behaviour, which results from a delayed response to the external load change. These results reasonably explain and correlate the physics behind the elastic limit, stick-slip shear band behaviour, implicit shear events, and shear band fracture in metallic glasses. The study can provide another perspective and platform to understand the correlations between structural inhomogeneity and shear band behaviours in metallic glasses, and further explore other shear band related phenomena not only in metallic glasses but also in the class of shear-softened materials.     

The electrical resistivity of amorphous alloys at low temperatures

Measurements of the temperature- and magnetic field dependence of the electrical resistance of some metallic glasses are presented. The data obtained for Cu₅₇Zr₄₃, Cu₄₀Zr₆₀ and Pd₃₀Zr₇₀ demonstrate that deviations from the high temperature behaviour extrapolated to low temperatures are caused by superconducting effects. The paraconductivity which is strongly enhanced in amorphous alloys is shown to agree quite well with theoretical models. The normal state resistance does not saturate down to temperatures of about 2 K. It still exhibits a negative temperature coefficient of the resistivity.     

Shear band formation and ductility in bulk metallic glass

The variations in the chemical compositions of the metallic glasses reported in the literature, as well as the overall lack of experimental data concerning the inhomogeneous deformation behaviour of metallic glass, make the evaluation of the effects of shear band/fracture behaviour on the mechanical properties of metallic glasses difficult. Isolating the effect of local shear band formation on bulk inhomogeneous flow would appear to be a first step in approaching this problem. The mechanical behaviour of Vitreloy metallic glass at room temperature and at various strain rates in tension and compression was investigated. The formation of multiple shear bands was observed at high strain rates. An increase in strain rate leads to enhanced ductility in tension and compression. Some aspects of the deformation processes in tension and compression are discussed.     

Extraordinary plasticity of ductile bulk metallic glasses

Shear bands generally initiate strain softening and result in low ductility of metallic glasses. In this Letter, we report high-resolution electron microscope observations of shear bands in a ductile metallic glass. Strain softening caused by localized shearing was found to be effectively prevented by nanocrystallization that is in situ produced by plastic flow within the shear bands, leading to large plasticity and strain hardening. These atomic-scale observations not only well explain the extraordinary plasticity that was recently observed in some bulk metallic glasses, but also reveal a novel deformation mechanism that can effectively improve the ductility of monolithic metallic glasses.     

金属玻璃Tg附近内耗理论分析

本文根据自由体积模型和固体材料的力学理论分析并讨论了金属玻璃在玻璃转变温度T_g附近的内耗行为。当考虑到体系中固状区和液状区的比例之后,得出了应力与应变之间的关系式。理论上把内耗和模量变化与玻璃转变过程有机地结合起来。证明了在T_g附近可以出现具有弛豫型特征的内耗降,并在玻璃转变过程中模量明显下降。理论与实验结果基本相符。 关键词：     

An interstitialcy theory of structural relaxation and related viscous flow of glasses

A theory of isothermal structural relaxation and creep of glasses below the glass transition temperature is given. According to the interstitialcy theory, the supercooled liquid state does not exist below a Kauzmann "pseudocritical" temperature T(k), which lies above the temperature T(K), commonly called the "Kauzmann temperature." Structural relaxation is simply a reduction with time of the interstitialcy concentration to the crystalline state for TT(k). The predicted viscosity eta is universal, given by eta=eta(0) + eta(T)t, in agreement with experiment. eta is continuous in T, with eta discontinuous at T(k) but linear in 1/T above and below T(k). The dependence of eta on the shear modulus directly connects kinetic and thermodynamic properties of glasses and liquids.     

Elastic heterogeneity in metallic glasses

When a stress is applied on a metallic glass it deforms following Hook's law. Therefore it may appear obvious that a metallic glass deforms elastically. Using x-ray diffraction and anisotropic pair-density function analysis we show that only about 3/4 in volume fraction of metallic glasses deforms elastically, whereas the rest of the volume is anelastic and in the experimental time scale deform without resistance. We suggest that this anelastic portion represents residual liquidity in the glassy state. Many theories, such as the free-volume theory, assume the density of defects in the glassy state to be of the order of 1%, but this result shows that it is as much as a quarter.