Al,Si,Mn,Cu杂质原子在纯Ni激光熔凝过程中的重新分布SCIEI

本文重点测量了Al,Si,Mn,Cu杂质原子在纯Ni激光慢速重熔过程中的重新分布。建立了一维传热的解析解模型。对杂质原子重新分布的规律提出了合理的解释。研究结果表明:固液界面溶质再分配是导致深度方向杂质原子重新分布的主要原因。此外,杂质原子从低温向高温区的扩散以及表面杂质原子的选择性蒸发对分布规律的形成也具有不可忽视的贡献。     

Theoretical study of interstitial atoms distribution in the bulk and at the surface of crystal. Surface segregation

A theoretical investigation of diffusion, distribution and thermally activated redistribution of impurity interstitial atoms C (hydrogen, carbon) about the volume and surface both of crystalline films and massive crystals AB has been carried out. These crystals have bcc lattice and various types of free facets. The dependence of hydrogen and carbon filling of the surface and volume interstitial sites upon the films’ temperature and composition have been studied. Changing the temperature or pressure leads to the redistribution of C atoms in the system. The thermally activated processes of C atom redistribution among the volumetric and surface film interstices in AB alloy are investigated. The formulae for the equilibrium concentrations of interstitial atoms and the rate or relaxation time of interstitial atoms redistribution in dependence on concentrations of A, B alloy components, on long range order in A, B atoms distribution at the sites of crystal lattice, on temperature, on interaction energies of atomic pairs AC, BC are determined.     

Intercrystalline internal adsorption in alloys based on α brass

Conclusions Elements S, Al, Mn, Sn, Ni, As, and Sb are susceptible to intercrystalline internal adsorption in brass. Internal adsorption of zinc on impurity atoms is possible. When impurity atoms pass into the zone of intercrystalline internal adsorption their size attains the average size of solvent atoms.Donets Physicotechnical Institute, Academy of Sciences of the Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 61–63, March, 1981.     

Effect of fine structure of Pb-In solid solutions on their deformation-induced strengthening at low temperatures

The specific features of low-temperature deformation-induced strengthening of Pb-In single crystals have been studied in a wide range of impurity concentrations. It was shown that a change in the strain-rate sensitivity of flow stress in the concentrated solid solution is connected with the inhomogeneous distribution of impurities. Based on the X-ray diffuse-scattering data, it was found that the short-range order of separation type was formed in these alloys; i.e., the lead atoms were randomly arranged and the indium atoms formed clusters whose characteristic size increased with concentration in a range of 1.0–1.9 nm. In the concentrated alloy, the appearance of coarse impurity clusters as strong obstacles for mobile dislocations in comparison with the impurity atoms and forest dislocations causes not only a sharp increase in the flow stress but also a change in the energy of dislocation-dislocation interaction.     

Analysis of refining of aluminum using fractional solidification with forced convection

Segregation of iron atoms during refining of aluminum using the fractional solidification technique has been analyzed. The redistribution of the solute atoms was influenced by the solidification and solid/liquid interface tangential velocities. Aluminum purity increased with decreasing solidification velocity and increasing tangential velocity. The diffusion boundary thickness was inversely proportional to the square root of the tangential velocity in the cylindrical rotating system. Effects of the tangential and solidification velocities on the effective redistribution coefficient were investigated. The calculated refining curves were in good agreement with measured values.     

Formation of nanoclusters of gadolinium atoms in silicon

A technology of stagewise low-temperature diffusion of gadolinium into silicon that makes it possible to form nanoclusters of impurity atoms with a significant magnetic moment distributed throughout the volume of the material has been developed. It is shown that, unlike the samples obtained by high-temperature diffusion doping, the samples prepared by the new technology do not have surface erosion, and alloys and silicides are not formed in the near-surface region. Nanoclusters of impurity atoms of gadolinium in the volume of the crystal lattice of the silicon are studied using an MIK-5 infrared microscope. It is found that, in the stagewise low-temperature diffusion, the temperature and time of the diffusion have an effect not only on the depth of penetration of the impurities but also on the sizes of the resulting clusters; these factors can also prevent the formation of clusters. The study of the effect of low-temperature treatments on the size and distribution of clusters shows that, upon annealing in the temperature range of 500–700°C, the ordering of the clusters of gadolinium impurity atoms is observed. A further increase in the annealing temperature leads to the destruction of gadolinium clusters in the silicon bulk.     

Redistribution of C and N Atoms in High Nitrogen Martensitic Stainless Steel During Cryogenic Treatment

The redistribution of C and N atoms during cryogenic treatment is crucial for the microstructure evolution and properties of high nitrogen martensitic steel. Here, the distinct redistribution behavior of C and N atoms in a martensitic stainless steel with 0.3 wt% C and 0.5 wt% N after cryogenic treatment were investigated by the atom probe tomography. Carbon clusters begin to form after cryogenic treatment at - 60 °C and gradually increase with the decrease of cryogenic treatment temperature. While Mo-N and Cr-N pairs are homogeneously distributed in the matrix even after cryogenic treatment at -120 °C, and then form enrichment phenomenon when the cryogenic temperature is deeply lowered to - 190 °C. It is found that the distinct redistributions of C and N atoms are associated with the different interaction energy between substitutional atoms and them. The stronger interaction between Cr, Mo atoms and N delays the segregation of N during the cryogenic treatment. Finally, the mechanical properties results confirmed that the deep lower cryogenic treatment is a promising method to improve the hardness and strength in the high nitrogen martensitic stainless steel.     

High pressure study of the intramolecular vibrational modes in sexithiophene single crystals

We report on the effects of a high hydrostatic pressure on the intra-molecular modes of a sexithiophene (T6) single crystal. Raman experiments were performed at low temperature up to a pressure of 80 kbar. We find that intermolecular interaction gives rise to a sizeable redistribution of the intensities of the strongest intra-molecular Raman lines. These changes are due to a slight deformation occurring in the terminal rings of the sexithiophene molecule. The frequencies of the bending modes involving sulfur atoms are the most affected by pressure. A Davydov doublet and a mixed inter/intra-molecular mode are observed. These results confirm the role played by the sulfur atoms in modulating the electronic overlap between chains.     

Elaboration of physical fundamentals of nanosized structures on the basis of S++Mn−− and Se++Mn−− molecule formation in silicon lattice

One possible way to create nanosized structures on the basis of the formation of molecules (S⁺⁺Mn^??) and (Se⁺⁺Mn^??) among impurity atoms S, Se, Mn in the silicon lattice is described in the work. Relationships between the concentration of molecules (S⁺⁺Mn^??) and (Se⁺⁺Mn^??) and the concentration of impurity atoms are established.     

Dynamic equilibrium of MoSi2 polymorphs during mechanical milling

The phase transformation of α-MoSi₂ into β-MoSi₂ induced by mechanical milling (MM) was studied. Planetary ball milling was performed on an α-MoSi₂ powder under six different milling conditions. The X-ray diffraction results show that the dynamic equilibrium between α-MoSi₂ and β-MoSi₂ is reached at low milling intensities, while a single phase of β-MoSi₂ is formed when milled at high milling intensities. The single-phase β-MoSi₂ formation is found to be due to Fe impurity. The mechanism of the phase transformation of MoSi₂ is discussed, and the phase fractions under the dynamic equilibrium are explained by the redistribution of the close-packed layers via synchroshear processes.     

微量杂质对高纯铝再结晶影响的Monte Carlo模拟

将微量杂质对再结晶的阻碍作用转化为再结晶自由能变化，从而建立微量杂质作用下的能量转化模型。采用Monte Carlo方法实现能量转化模型的数值模拟，结果表明，微量杂质元素含量的波动对再结晶晶粒长大的影响很大。并与高纯铝实验结果进行了对比，对比表明模拟结果与实验结果很吻合。     

Fe中刃型位错及其掺杂体系的电子结构

用DMol团簇方法研究了bccFe［100］（010）刃型位错及其掺杂（碳,氮,磷）体系的电子结构,给出了Fe中刃型位错及其掺杂体系的能量参数（结合能、格位能及杂质形成能）和掺氮体系的差分电荷密度,结果表明,杂质与位错芯区近邻基体原子间存在电荷关联区,它反映了位错芯区轻杂质及其近邻基体原子间存在相互作用,Fe中刃型位错芯区能量计算表明：位错芯区具有捕获轻杂质（碳,氮,磷）的作用,反映了Cottrell气团的量子力学效应。     

有害杂质（Al,Ti）对铁基非晶磁性的影响及其改善方法

介绍了非晶合金中的微量元素Ａｌ和Ｔｉ对铁基非晶薄带磁性的影响及薄带表面结晶形态与磁性的关系，分析了有害杂质Ａｌ、Ｔｉ作用机理。指出可添加微量Ｓｎ和Ｓ来抑制Ａｌ和Ｔｉ的有害作用，能使合金磁性能得到恢复，达到可用低纯度原料来生产优质磁性非晶带材的目的。     

低温固体渗硼的渗层形貌与元素的再分布

利用Ｘ射线衍射仪、电子探针研究了低温固体渗硼的渗层形貌、相组成和元素的再分布特征。结果表明，低温固体渗硼的硼化层是由ＦｅＢ、Ｆｅ２Ｂ、Ｆｅ３（Ｃ，Ｂ）、Ｆｅ３（Ｓｉ，Ｂ）等相组成。硼化层的前沿无过渡区，ＦｅＢ和Ｆｅ２Ｂ生长过程中排挤出来的碳和硅没有发生远程扩散，而是就近形成Ｆｅ３（Ｃ，Ｂ）和Ｆｅ３（Ｓｉ，Ｂ）等形式的含碳和硅的硼化物。     

On the concentration maxima of nonequilibrium point defects in irradiated copper with an impurity of gold

Results of a numerical solution based on a model that describes the process of accumulation of radiation-induced point defects in metals with impurities are presented. It has been established that a twofold increase in the energy of migration of interstitial atoms in copper with an impurity of gold results in a 40-fold increase in the excess concentration of interstitial atoms.     

Interstitial distribution in Fe–Al and Fe–Cr quenched and aged alloys:: Computer simulation and internal friction study

Two types of physical approaches for simulation of the Snoek-type relaxation in low and high alloyed iron are examined to explain the experimental results obtained for Fe–Al–C and Fe–C–Cr alloys. The first approach developed by Smirnov–Tomilin is to calculate all octahedral positions available for interstitial atoms with different amount of substitute atoms in the first coordination shell and to simulate the loss maximum as a sum of all partial peaks according to the above mentioned interstice positions. The second approach takes into account the all pairwise interatomic interaction between solute atoms in a few coordination shells due to their interatomic elastic and ‘chemical’ interaction according to Khachaturyan–Blanter theory. The change of activation energy of ‘diffusion under the stress’ for interstitial atoms in that case is not a linear function of substitutional concentration in solution. Both physical models (short- and long-range interatomic interaction) for the Snoek-type relaxation in quenched ternary alloys (Fe–C–Me) are examined from the viewpoint of a distance of interatomic interaction taken into account and checked using experiments. It is shown that contrary to the second approach, the first type of calculations is reasonable for relatively low alloyed solid solution only. Decomposition (Fe–Cr) and ordering (Fe–Al) change the parameters of atomic distribution in bcc solid solution and lead to the corresponding change in the Snoek relaxation parameters. The use of an adequate physical model and structure parameters allows to explain corresponding effects and, vice versa, the internal friction spectrum allows to estimate quantitatively atom redistribution in alloyed ferrite.     

X-ray photoelectron spectroscopy of ceramic composites Bi,Pb-2223/Ag annealed in an atmosphere with a reduced content of oxygen (7.5% O<Subscript>2</Subscript> + 92.5% N<Subscript>2</Subscript>)

X-ray photoelectron spectroscopy (XPS) has been used to study (001) textured ceramic composites Bi,Pb-2223/Ag after high-temperature annealing in an atmosphere with a reduced oxygen content (7.5% O₂ + 92.5% N₂). Discussion is performed of the chemical and charge states of heavy atoms (Bi, Pb, Sr, Ca, Cu) and light atoms (of the main element (oxygen) and impurity element (carbon)) under conditions of oxygen deficit in the lattice.     

Relaxations and bonding mechanism of arsenic in-situ impurities in MCT： first-principles study

1 Introduction Mercury cadmium telluride (Hg1?xCdxTe, MCT) is currently one of the most widely used semiconductor materials for infrared detector arrays. It is well known that the applications of the semiconductor materials, especially for Ⅱ-Ⅵ compound…     

V-5Cr-5Ti合金的内耗特征研究

研究了不同处理状态下V-5Cr-5Ti合金的内耗特征,并结合微观缺陷的作用机制对内耗峰进行分析。利用倒扭摆仪和多功能内耗测试仪进行内耗测试,采用X射线衍射(XRD)分析相结构,扫描电镜(SEM)观察微观组织。研究结果表明,V-5Cr-5Ti合金制备过程中无法完全消除C、O、N等杂质元素,这些元素会以间隙原子或沉淀相颗粒形式存在,进而影响合金的微观组织缺陷。在不同的处理状态下,杂质元素的不同存在形式会使合金的内耗会产生不同的变化特征。根据内耗机制,所有的内耗峰均可以由应力作用下微观缺陷的运动来揭示,比如点缺陷、位错、晶界等。     

Interaction of radiation defects with nickel atom clusters in silicon

Based on infrared microscopic studies, we show that clusters of impurity nickel atoms are uniformly distributed over the entire volume of the silicon crystal; by varying the density of the clusters in silicon exposed to γ-radiation, it is possible to control the concentration of the electroactive atoms and the structure of the nickel clusters. It is shown that the presence of clusters in the lattice significantly increases the radiation resistance of the silicon.