共查询到17条相似文献,搜索用时 187 毫秒
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本文叙述了用偏振中子衍射方法对Fe83B17非晶合金和中子衍射方法对Ni64B36非晶合金的结构研究。由实验数据计算了每种合金的偏干涉函数(PSF)Sij(Q),和偏简约径向分布函数Gij(r)。并得到原子短程结构上的各项参数。在此基础上,讨论了这一类非晶态合金的结构模型,计算了其一种模型简单单元的中子衍射散射强度,并和实验所得的结果作了比较。
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本工作用X射线散射技术研究了金属一类金属玻璃合金Pd77Si16.5Ag6.59,Co42.9Ni27.3Fe7.8Si8B14和Co50.7Ni19.5Fe7.8Si6B16的结构。求出了它们的干涉函数I(s)和原子径向分布函数RDF(r),并由此获得了有关结构信息的原子平均距离、最近邻配位数和短程有序畴半径。此外,对这些合金的RDF(r)第一峰作了高斯分布拟合,求得了比较好的拟合方程,并用近似方法估算了其中金属-金属原子间的配位数。
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本文研究了经局部塑性变形后, Fe78Si9B13金属玻璃在原子尺度上的结构演变及其对合金显微硬度的影响.借助砂纸作为传力的媒介,充分放大了作用于带材表面上的等效压力,发生塑性变形后合金表面产生了大量的剪切带.基于倒空间和实空间的同步辐射X射线衍射分析,在塑性变形后,合金结构的致密度增大,过剩自由体积被排出,并由此揭示了Fe78Si9B13金属玻璃在短程及中程尺度上原子协同重排行为.结合高分辨透射电子显微镜观察的结果, Fe78Si9B13金属玻璃在发生塑性变形后,结构不均匀的程度将会加剧.此外,不同于单轴加载下金属玻璃的加工软化, Fe78Si9B13金属玻璃在发生局部塑性变形后,维氏硬度增大,表现出局部的加工硬化行为.从自由体积的角度看,合金表面的大量剪切带可能是由于剪切带影响区域的重叠和交叉发生相互作用,并加速原子迁移,... 相似文献
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The local environment of Cu atoms in Fe73.5Cu1Nb3Si13.5B9 alloy was investigated by extended X-ray absorption fine structure(EXAFS).Cu clusters began to order when the annealing temperature was around 733 K from the results of the Fourier transform curves.The fitting results showed that the first shell of the near fcc(face-centered cubic)Cu clusters only contained Cu atoms.The coordination number increased with the annealing temperature.Subsequently,the occupancy rate increased from 33.3%(annealed at 733 K)to 100% (annealed at 853 K).This local structural change of Cu atoms could probably affect the distribution of the bcc(body-centered cubic)α-Fe in Fe73.5Cu1Nb3Si13.5B9 alloy. 相似文献
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M. De Crescenzi A. Balzarotti F. Comin L. Incoccia S. Mobilio N. Motta 《Solid State Communications》1981,37(12):921-923
The EXAFS structure measured above the K-edge of Fe in the disordered Fe80B20 alloy is reported. Complete agreement is obtained with X-ray diffraction results in the position of the first neighbours coordination shell when the asymmetry of the Radial Distribution Function (R.D.F.) into the EXAFS formula is included. A Finney-like R.D.F. is used to describe the pair distribution of these metallic glasses. The weak temperature dependence of the spectra is discussed in terms of the structural properties of these amorphous alloys. 相似文献
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Results of thermal expansion prediction from atomic scale for metastable liquid metals are reported herein. Three pure liquid metals Ni, Fe, and Cu together with ternary Ni60Fe20Cu20 alloy are used as models. The pair distribution functions were employed to monitor the atomic structure. This indicates that the simulated systems are ordered in atomic short range and disordered in long range. The thermal expansion coefficient was computed as functions of temperature and atom cutoff radius, which tends to maintain a constant when the cutoff radius increases to approximately 15 Å. In such a case, slightly more than 1000 atoms are required for liquid Ni, Cu, Fe and Ni60Fe20Cu20 alloy, that is, the macroscopic thermal expansion can be predicted from the volume change of such a tiny cell. Furthermore, the expansion behaviors of the three types of atoms in liquid Ni60Fe20Cu20 alloy are revealed by the calculated partial expansion coefficient. This provides a fundamental method to predict the macroscopic thermal expansion from the atomic scale for liquid alloys, especially in the undercooled regime. 相似文献
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The amorphous ferromagnet Fe81B13.5Si3.5C2 (Metglas® 2605SC) has been investigated with Mössbauer spectroscopy. The hyperfine interaction parameters are studied between 80 and 300 K from which some characteristic properties are deduced. The behaviour of the amorphous alloy at higher temperatures has been studied by the room temperature spectra of annealed samples. After a structural relaxation process, a two step crystallization transformation is observed leading to Fe-Si alloy and Fe2(B, C). X-ray diffraction of samples annealed at higher temperatures reveals the presence of an orthorhombic Fe-B-Si phase of which the structure changes slightly with annealing temperature. 相似文献
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Borivoj Adna?evi? Bojan Jankovi? Dragica M. Mini? 《Journal of Physics and Chemistry of Solids》2010,71(7):927-985
Kinetics of the apparent isothermal and the non-isothermal crystallization of α-Fe phase within the amorphous Fe81B13Si4C2 alloy were investigated by an X-ray diffraction (XRD) and by a differential scanning calorimetry (DSC). It was established that the apparent isothermal crystallization of α-Fe phase within amorphous Fe81B13Si4C2 alloy could be described by the Johnson-Mehl-Avrami (JMA) kinetic model (with parameter niso=4.0). The apparent isothermal crystallization process includes a constant rate of nucleation and three-dimensional growth of nuclei. The results of X-ray diffraction (XRD) data of the isothermally crystallized samples confirmed the above established kinetic model. From the kinetic analysis of the non-isothermal crystallization of the α-Fe phase within this amorphous alloy, it was concluded that the autocatalytic two-parameter Šesták-Berggren (SB) reaction model (with kinetic exponents M=0.72 and N=1.02) describes well the studied process under the given conditions. The non-isothermal crystallization process involves the constant nucleation rate of stable nuclei with additional secondary two-dimensional (surface) nucleation and overlapping of the growing nuclei on account of the non-isothermal activation. 相似文献
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用转靶X射线源及弯晶EXAFS谱仪测定了Fe80B20及Fe80Si6B14金属玻璃中铁的X射线K吸收谱。由EXAFS谱确定了两种金属玻璃的近邻结构参量。此外,通过测定XANES谱并与纯铁及其有关的化合物Fe2B,FeB中铁的XANES比较发现:吸收边能量、“白线”结构等均出现一些变化,表明两种金属玻璃的近邻原子Fe-B,Fe-Si以及Fe-Fe之间的相互作用比铁与硼所形成的稳定化合物中要强,这对于决定金属玻璃的短程序结构具有重要的作用。
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