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Evolution of Microstructure and Ordering in Rolling Process of Fe-6. 5 mass% Si Alloy

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Journal of Iron and Steel Research International 2016年第5期23卷 453-458页

作者： Hui LI yong-feng LIANG feng YE State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

Fe-6. 5 mass% Si alloy is an excellent soft magnetic material with good application prospects. After rolling,the structure of the sheet is likely to be heterogeneous along the normal direction. The microstructure and ordering evolution in the thickness range of the sheets during hot-warm rolling process was studied by means of optical microscope and transmission electron microscope. The results show that dynamic recrystallization occurs in the surface parts during the hot and warm rolling processes,where the grains are equiaxed but have high density of dislocations due to the large deformation. The grains in the center part are elongated along the rolling direction. It is also found that in the hot rolled sheet,the center part has lower density of dislocations because of dynamic recovery. Meanwhile,this part has higher ordering content compared with the surface part,indicating that the high density of dislocations can inhibit the formation of ordering in the air cooling process after hot rolling. In the warm rolling process,both of the parts are deformed heavily. Large deformation destroys ordered phases and induces disordering. The ordering content is low in the whole warm rolled sheet.

关键词： rolling process microstructure ordering Fe-6.5 mass% Si alloy

Reduced spin-down rate of PSR J0738–4042 explained as due to an asteroid disruption event

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Research in Astronomy and Astrophysics 2016年第5期16卷 41-46页

作者： yong-Bo Yu yong-feng Huang Department of Astronomy Nanjing UniversityNanjing 210046China Key Laboratory of Modern Astronomy and Astrophysics(Nanjing University) Ministry of EducationNanjing 2 1 0046China

Long term observations by Brook et al. reveal that the derivative of rotational frequency of PSR J0738-4042 changed abruptly in 2005. Originally, the spin-down rate was relatively stable, with the rotational frequency derivative being - 1.14 x 10-14 s-2. After September 2005, the derivative began to rise. About 1000 days later, it arrived at another relatively stable value of about -0.98 x 10-24 s-2, indicating that the pulsar is spinning-down relatively slowly. To explain the observed change in spin-down rate, we resort to an asteroid disrupted by PSR J0738-4042. In our model, the orbital angular momentum of the asteroid is assumed to be parallel to that of the rotating pulsar, so that the pronounced reduction in the spin-down rate can be naturally explained as due to the transfer of angular momentum from the disrupted material to the central pulsar. The derived magnetospheric radius is about 7.0 x 109 cm, which is smaller than the tidal disruption radius （8.7 x 10^10cm）. Our model is self-consistent. It is shown that the variability in the spin-down rate of PSR J0738-4042 can be quantitatively accounted for by accretion from the asteroid disrupted by the central pulsar.

关键词： stars: neutron -- planet-star interactions -- pulsars: individual (PSR J0738-4042)

A two-step energy injection explanation for the rebrightenings of the multi-band afterglow of GRB 081029

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Research in Astronomy and Astrophysics 2013年第6期13卷 662-670页

作者： yong-Bo Yu yong-feng Huang Department of Astronomy Nanjing University Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University) Ministry of Education

The afterglow of GRB 081029 showed unusual behavior, with a signifi- cant rebrightening being observed at the optical wavelength at about 3000 s after the burst. One possible explanation is that the rebrightening resulted from an energy in- jection. Here we present a detailed numerical study of the energy injection process and interpret the X-ray and optical afterglow light curves of GRB 081029. In our model, we have assumed two periods of energy injection, each with a constant injec- tion power. One injection starts at 2.8 × 10^3 s and lasts for about 2500 s, with a power of 7.0 × 10^47 erg s-1. This energy injection mainly accounts for the rapid rebrighten- ing at about 3000 s. The other injection starts at 8.0 × 10^3 s and lasts for about 5000 s. The injection power is 3.5 × 10^47 erg s-1. This energy injection can help to explain the slight rebrightening at about 10 000 s. It is shown that the observed optical after- glow, especially the marked rebrightening at about 3000 s, can be reproduced well. In the X-ray band, the predicted amplitude of the rebrightening is much shallower, which is also consistent with the observed X-ray afterglow light curve. It is argued that the two periods of energy injection can be produced by clumpy materials falling onto the central compact object of the burster, which leads to an enhancement of accretion and gives rise to a strong temporary outflow.

关键词： gamma-rays: bursts -- ISM: jets and outflows -- individual:GRB 081029

Fractionation of Polyolefin Elastomer by a Modified SSA Technique

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Chinese Journal of Polymer Science 2022年第10期40卷 1252-1258,I0010页

作者： Xin-Tong Zhao yong-feng Men State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China Schoolof Applied Chemistry and Engineering University of Science and Technology of ChinaHefei 230026China

As an important part of semicrystalline polymer materials,polyolefin elastomers are widely used,and the in-depth analysis of their molecular chain structure information is of great significance to promote their rapid *** show in this work an effort in characterizing a commercial polyolefin elastomer of ethylene/1-octene copolymer by a modified successive self-nucleation and annealing(SSA)technique.A small amount of linear polyethylene was blended with the ethylene/1-octene copolymer serving as nucleation agent during *** turned out that a tiny fraction of linear polyethylene can significantly promote the crystallization of the copolymer during cooling from different annealing temperatures and increase the melting temperature of the fractions so that providing apparent methylene sequence length much closer to the real value than obtained by traditional SSA technique.

关键词： Polyolefin elastomer Ethylene-co-octene Thermal fractionation SSA Micro structure

Visualizing Planar and Space Implicit Real Algebraic Curves with Singularities

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Journal of Systems Science & Complexity 2020年第4期33卷 1252-1274页

作者： CHEN Changbo WU Wenyuan feng yong Chongqing Key Laboratory of Automated Reasoning and Cognition Chongqing Institute of Green and Intelligent TechnologyChinese Academy of SciencesChongqing 400714China University of Chinese Academy of Sciences Beijing 100049China

This paper presents a new method for visualizing implicit real algebraic curves inside a bounding box in the 2-D or 3-D ambient space based on numerical continuation and critical point methods. The underlying techniques work also for tracing space curve in higher-dimensional *** the topology of a curve near a singular point of it is not numerically stable, the authors trace only the curve outside neighborhoods of singular points and replace each neighborhood simply by a point, which produces a polygonal approximation that is ε-close to the curve. Such an approximation is more stable for defining the numerical connectedness of the complement of the projection of the curve in R2, which is important for applications such as solving bi-parametric polynomial *** algorithm starts by computing three types of key points of the curve, namely the intersection of the curve with small spheres centered at singular points, regular critical points of every connected components of the curve, as well as intersection points of the curve with the given bounding box. It then traces the curve starting with and in the order of the above three types of points. This basic scheme is further enhanced by several optimizations, such as grouping singular points in natural clusters, tracing the curve by a try-and-resume strategy and handling "pseudo singular points". The effectiveness of the algorithm is illustrated by numerous examples. This manuscript extends the proposed preliminary results that appeared in CASC 2018.

关键词： singular neighborhood intersection

Initiation, Development and Stabilization of Cavities during Tensile Deformation of Semicrystalline Polymers

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Chinese Journal of Polymer Science 2018年第10期36卷 1195-1199页

作者： Ying Lu yong-feng Men State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 130022 China University of Science and Technology of China Hefei 230026 China

By using polybutene-1 as a typical example, we illustrate the initiation, development and stabilization of cavities in the sample during tensile deformation. Samples with the same crystallinity, long spacing and crystalline lamellar thickness but very different sizes of spherulites were prepared via changing the melt history. Dimension of cavities during stretching the samples was determined by in situ ultra small angle X-ray scattering techniques. It turned out that the size of the cavities was bigger in the sample with larger spherulites than the one with smaller spherulites. The results show clear evidence of initiating cavities within crystalline phase at the grain-boundary of crystalline blocks, growing of cavities passing through parallel stacked lamellar crystals and amorphous layers and finally stablized by tilted lamellae at both ends of the plate-like cavities within the spherulites.

关键词： Cavitation Deformation Polymer Polubutene-1 Spherulite

Microstructure evolution of a new near-β titanium alloy:Ti555211 during high-temperature deformation

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Rare Metals 2015年第11期34卷 757-763页

作者： Zhen An Jin-Shan Li yong feng State Key Laboratory of Solidification Processing Northwestern Polytechnical University

The isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 ℃ in 50 ℃ intervals,with strain rate of 0.001-1.000 s-1and height reduction of 20%-60%.The effect of processing parameters（deformation temperature,strain rate and deformation degree） on the microstructure evolution and the microstructure variables was *** results show that the content of primary α phase decreases with the increase in deformation *** effect of strain rate on microstructure variables of isothermally compressed Ti555211 alloy is mainly dependent on the deformation *** fine second α phase partly transforms to β phase due to the deformation heat effect at the high strain rate,α phase becomes globular with temperature increasing and strain rate *** contrast,α phase is refined with temperature decreasing and strain rate *** deformation degree has a little influence on the grain size and the morphology of primary α phase,but the effect of deformation degree on the morphology of second α phase is *** larger deformation degree is in favor of the globularization of lamellar α structure.

关键词： Titanium alloy High-temperature deformation Micros

Optimization of thermal processing parameters of Ti555211 alloy using processing maps based on Murty criterion

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Rare Metals 2016年第2期35卷 154-161页

作者： Zhen An Jin-Shan Li yong feng State Key Laboratory of Solidification Processing Northwestern Polytechnical University

Isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 °C in 50 °C intervals with a strain rate of0.001-1.000 s^（-1）. The high-temperature deformation behavior of the Ti555211 alloy was characterized by analysis of stress-strain behavior, kinetics and processing maps. A constitutive equation was formulated to describe the flow stress as a function of deformation temperature and strain rate, and the calculated apparent activation energies are found to be 454.50 and 207.52 k J mol^（-1）in the a b-phase and b-phase regions, respectively. A processing map based on the Murty instability criterion was developed at a strain of 0.7. The maps exhibit two domains of peak efficiency from 750 to 950 °C. A ＊60 % peak efficiency occurs at 800-850 °C/0.001-0.010 s^（-1）. The other peak efficiency of ＊60 % occurs at C950 °C/0.001-0.010 s^（-1）, which can be considered to be the optimum condition for high-temperature working of this ***, at strain rates of higher than 1.000 s^（-1）and deformation temperatures of 750 and 950 °C, clear process flow lines and bands of flow localization occur in the hightemperature deformation process, which should be avoided in Ti555211 alloy hot processing. The mechanism in stability domain and instability domain was also discussed.

关键词： Ti555211 titanium alloy High temperature Deformation behavior Processing maps

PHASE BEHAVIOR OF CHARGE STABLIZED COLLOID DISPERSION WITH ADDED WATER SOLUBLE POLYMERS

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Chinese Journal of Polymer Science 2013年第9期31卷 1218-1224页

作者： Jia-xue Liu yong-feng Men State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences University of Chinese Academy of Sciences

Demixing and colloidal crystallization in the mixture of charge stabilized colloidal poly（methyl methacrylate） particles and soluble poly（ethylene oxide） were investigated by means of synchrotron small-angle X-ray scattering （SAXS） technique. Phase diagram of the mixture was obtained based on visual inspection and SAXS results. The phase behavior is determined as a function of the concentration of the polymer as well as the volume fraction of the colloidal particles. The system shows a one phase region when the concentration of the polymer is low, whereas a two-phase region is present when the concentration of the polymer is larger than a critical concentration at certain volume fraction of the colloids. Interestingly, a face centered cubic colloidal crystalline structure was formed under certain conditions, which has been rarely observed in experiments of colloid-polymer mixtures with competing interactions.

关键词： Colloid-polymer mixture Phase behavior Crystallization.