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International Journal of Minerals,Metallurgy and Materials 2012年第7期19卷 608-614页

作者： Jun Yao Xuan-hui Qu xin-bo he Lin Zhang State Key Laboratory for Advanced Metals and Materials School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083China

The fatigue strength of a high V alloyed powder metallurgy tool steel with two different inclusion size levels, tempered at different temperatures, was investigated by a series of high cycle fatigue tests. It was shown that brittle inclusions with large sizes above 30μm prompted the occurrence of subsurface crack initiation and the reduction in fatigue strength. The fracture toughness and the stress amplitude both exerted a significant influence on the fish-eye size. A larger fish-eye area would form in the sample with a higher fracture toughness subjected to a lower stress amplitude. The stress intensity factor of the inclusion was found to lie above a typical value of the threshold stress intensity factor of 4 MPa.m^1/2. The fracture toughness of the sample with a hardness above HRC 56 could be estimated by the mean value of the stress intensity factor of the fish-eye. According to fractographic evaluation, the critical inclusion size can be calculated by linear fracture mechanics.

关键词： powder metallurgy tool steel fatigue of materials strength of materials failure modes inclusions fractography

Preparation of CaB6 powder via calciothermic reduction of boron carbide

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International Journal of Minerals,Metallurgy and Materials 2020年第1期27卷 37-45页

作者： Yu Wang Guo-hua Zhang Yue-dong Wu xin-bo he State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing 100083China Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing 100083China

The method of calciothermic reduction of B4C was proposed for preparing *** phase transition and morphology evolution during the reaction were investigated in *** experimental results reveal that Ca first reacts with B4C to generate CaB2C2 and CaB6 at a low temperature and that the CaB2C2 subsequently reacts with Ca to produce CaB6 and CaC2 at a high *** the products were leached to remove the byproduct CaC2,pure CaB6 was *** grain size of the prepared CaB6 was 2–3μm,whereas its particle size was 4–13μm;it inherited the particle size of *** residual C content of the product was decreased to 1.03 wt%after the first reaction at 1173 K for 4 h and the second reaction at 1623 K for 4 h.

关键词： borides carbides particle size powders calcium hexaboride

Preparation,crystallization,and wetting of ZnO-Al_2O_3-B_2O_3-SiO_2 glass-ceramics for sealing to Kovar

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International Journal of Minerals,Metallurgy and Materials 2009年第5期16卷 586-591页

作者： Mao Wu xin-bo he Zhuo-shen Shen Xuan-hui Qu School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

A novel type of ZnO-Al2O3-B2O3-SiO2 glass-ceramics sealing to Kovar in electronic packaging was developed, whose thermal expansion coefficient and electrical resistance are 5.2× 10^-6/℃ and over 1×10^13 Ω·cm, respectively. The major crystalline phases in the glass-ceramic seals were ZnAl2O4, ZnB2O4, and NaSiAl2O4. The dielectric resistance of the glass-ceramic could be remarkably enhanced through the control of alkali metal ions into crystal lattices. It was found that crystallization happened first on the surface of the sample, leaving the amorphous phase in the inner, which made the glass suitable for sealing. The glass-ceramic showed better wetting on the Kovar surface, and sealing atmosphere and temperature had great effect on the wetting angle. Strong interracial bonding was obtained, which was mainly attributed to the interracial reaction between SiO2 and FeO or Fe3O4.

关键词： electronic packaging materials glass-ceramic crystallization wetting sealing

GRB 170817A: a short GRB seen off-axis

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Research in Astronomy and Astrophysics 2018年第4期18卷 69-76页

作者： xin-bo he Pak-Hin Thomas Tam Rong-Feng Shen School of Physics and Astronomy Sun Yat-sen University

The angular distribution of gamma-ray burst（GRB）jets is not yet *** observed luminosity of GRB 170817A is the lowest among all known short GRBs,which is best explained by the fact that our line of sight is outside of the jet opening angle,θ_（obs）〉θ_j,whereθ_（obs） is the angle between our line of sight and the jet *** inferred by gravitational wave observations,as well as radio and X-ray afterglow modeling of GRB 170817A,it is likely that θ_（obs）~20°–28°.In this work,we quantitatively consider two scenarios of angular energy distribution of GRB ejecta：a top-hat jet and a structured jet with a power law index *** the top-hat jet model,we get a large θ_j（e.g.,θ_j〉10°）,a rather high local （i.e., z 〈 0.01） short GRB rate ~8–15×10~3 Gpc^（-3）yr~（-1（（estimated to be 90~1850 Gpc^（-3）yr^（-1） in Fong et al.）and an extremely high（on-axis,V（~500 ke V for a typical short GRB）.For the structured jet model,we use θ_（obs） to give limits on s and θ_j for typical on-axis luminosity of a short GRB（e.g.,10^（49）erg s（-1） 1051erg s（-1））,and a low on-axis luminosity case（e.g.,1049erg s（-1））gives more reasonable values of *** structured jet model is more feasible for GRB170817A than the top-hat jet model due to the rather high local short GRB rate,and the extremely high on-axis E_（peak,0） almost rules out the top-hat jet *** 170817A is likely a low on-axis luminosity GRB（1049erg s（-1））with a structured jet.

关键词： short gamma-ray burst individual(GRB 170817A) — gravitational wave

Effect of Mg and Si on infiltration behavior of Al alloys pressureless infiltration into porous SiCp preforms

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International Journal of Minerals,Metallurgy and Materials 2011年第6期18卷 703-708页

作者： Shu-bin Ren Xiao-yu Shen Xuan-hui Qu xin-bo he School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

The effect of Mg and Si additon to Al matrix on infiltration kinetics and rates of Al alloys pressureless infiltration into porous SiCp preform was investigated by observing the change of infiltration distance with time as the Al alloys infiltrate into SiCp preforms at different *** results show that infiltration of SiCp preforms by Al melt is a thermal activation process and there is an incubation period before the infiltration becomes *** the increase of Mg content in the Al alloys from 0wt% to 8wt%,the infiltration will become much easier,the incubation period becomes shorter and the infiltration rate is faster,but these effects are not obvious when the Mg content is higher than 8wt%.As for Si addition to the Al alloys,it has no obvious effect on the incubation period,but the infiltration rate increases markedly with the increase of Si content from 0wt% to 12wt% and the rate has no obvious change when the content is bigger than 12wt%.The effect of Mg and Si on the incubation period is related to the infiltration mechanism of Al pressureless infiltration into SiCp preforms and their impact on the infiltration rate is a combined result from viscosity and surface tension of Al melt and SiC-Al wetting ability.

关键词： metallic matrix composites infiltration aluminum alloys silicon carbide preforms

Thermal properties of diamond/Al composites by pressure infiltration:comparison between methods of coating Ti onto diamond surfaces and adding Si into Al matrix

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Rare Metals 2016年第3期35卷 249-255页

作者： Cai-Yu Guo xin-bo he Shu-Bin Ren Xuan-Hui Qu Institute for Advanced Materials and Technology University of Science and Technology Beijing

This study was pertained to the effects of Ti coating on diamond surfaces and Si addition into Al matrix on the thermal conductivity（TC） and the coefficient of thermal expansion（CTE） of diamond/Al composites by pressure *** fracture surfaces,interface microstructures by metal electro-etching and interfacial thermal conductance of the composites prepared by two methods were *** results reveal that Ti coating on diamond surfaces and only12.2 wt% Si addition into Al matrix could both improve the interfacial bonding and increase the TCs of the *** the Ti coating layer introduces more interfacial thermal barrier at the diamond/Al interface compared to adding 12.2 wt% Si into Al *** diamond/Al composite with 12.2 wt% Si addition exhibits maximum TC of 534 W·m^-1·K^-1and a very low CTE of 8.9×10^-6K^-1,while the coating Ti-diamond/Al composite has a TC of 514 W·m^-1·K^-1 and a CTE of 11.0×10^-6K^-1.

关键词： Metal matrix composites Coating Thermal conductivity Coefficient of thermal expansion Pressure infiltration

Microstructure characterization of a pressureless infiltrating oxidized SiCp preform by Al-8Mg

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International Journal of Minerals,Metallurgy and Materials 2011年第2期18卷 223-228页

作者： Shu-bin Ren Xiao-yu Shen xin-bo he Xuan-hui Qu School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

The microstructure of a pressureless infiltrating 55vol% oxidized SiC preform by Al-8Mg alloy was characterized by transmission electron microscopy （TEM）, high resolution TEM （HRTEM）, field emission scanning electron microscopy （FE-SEM）, and X-ray diffraction. The TEM image of the interface between Al and SiC shows that the surface of SiC is covered by a rough nanocrystal layer of MgAl2O4, Al2O3, and Si, produced by the interfacial reaction of Al, Mg, and SiO2 on the surface of SiC. The Al-SiC interface is also examined by HRTEM to be better understood how MgAl2O4 and Al2O3 are produced. Dendritic Al2O3 crystals are embedded in the pores of the composite generated from the mutual bonding of SiO2 on the surface of SiC. Columnar AlN crystals of about 250 nm in length are bunched vertically on the SiC particle surface.

关键词： microstructure composites interfaces pressureless infiltration oxidation.

Sintering behavior and thermal conductivity of nickel-coated graphite flake/copper composites fabricated by spark plasma sintering

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International Journal of Minerals,Metallurgy and Materials 2018年第4期25卷 459-471页

作者： Hui Xu Jian-hao Chen Shu-bin Ren xin-bo he Xuan-hui Qu Institute for Advanced Materials and Technology University of Science and Technology Beijing

Nickel-coated graphite flakes/copper（GN/Cu） composites were fabricated by spark plasma sintering with the surface of graphite flakes（GFs） being modified by Ni–P electroless plating. The effects of the phase transition of the amorphous Ni–P plating and of Ni diffusion into the Cu matrix on the densification behavior, interfacial microstructure, and thermal conductivity（TC） of the GN/Cu composites were systematically investigated. The introduction of Ni–P electroless plating efficiently reduced the densification temperature of uncoated GF/Cu composites from 850 to 650℃ and slightly increased the TC of the X–Y basal plane of the GF/Cu composites with 20 vol%–30 vol% graphite flakes. However, when the graphite flake content was greater than 30 vol%, the TC of the GF/Cu composites decreased with the introduction of Ni–P plating as a result of the combined effect of the improved heat-transfer interface with the transition layer, P generated at the interface, and the diffusion of Ni into the matrix. Given the effect of the Ni content on the TC of the Cu matrix and on the interface thermal resistance, a modified effective medium approximation model was used to predict the TC of the prepared GF/Cu composites.

关键词： copper matrix composites graphite flake nickel-phosphorus transition layer sintering behavior thermal conductivity

Microstructure and thermal properties of copper matrix composites reinforced with titanium-coated graphite fibers

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Rare Metals 2013年第1期32卷 75-80页

作者： Hao-Ming Zhang xin-bo he Xuan-Hui Qu Qian Liu Xiao-Yu Shen School of Materials Science and Engineering University of Science and Technology Beijing State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

Milled form of mesophase pitch-based graphite fibers were coated with a titanium layer using chemical vapor deposition technique and Ti-coated graphite fiber/Cu composites were fabricated by hot-pressing sintering. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopies, and by mea- suring thermal properties, including thermal conductivity and coefficient of thermal expansion （CTE）. The results show that the milled fibers are preferentially oriented in a plane perpendicular to the pressing direction, leading to anisotropic thermal properties of the composites. The Ti coating reacted with graphite fiber and formed a continuous and uniform TiC layer. This carbide layer establishes a good metallurgical interracial bonding in the composites, which can improve the thermal properties effectively. When the fiber content ranges from 35 vol% to 50 vol%, the in-plane thermal conductivities of the composites increase from 383 to 407 W.（m.K）-~, and the in-plane CTEs decrease from 9.5 x 10-6 to 6.3 10-6 K-1.

关键词： Metal matrix composites Titanium coating Microstructure Thermal conductivity Coefficient of thermal expansion

Direct ink writing of TiC-316L metal matrix composites with an epoxy resin-absolute ethanol system

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Rare Metals 2021年第3期40卷 590-599页

作者： Tao Lin Liu-Ping Jin Jia-Yun Yuan Hui-Ping Shao Fu-Cheng Yu Wen-Yuan Li xin-bo he xin Deng Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing 100083China School of Material Science and Engineering Lanzhou University of TechnologyLanzhou 730050China Jihua Laboratory Chengye MansionFoshan 528299China School of Electromechanical Engineering Guangdong University of TechnologyGuangzhou 510006China

TiC-316 L metal matrix composites were successfully printed with an epoxy resin-absolute ethanol system by direct ink writing(DIW) process in this *** and fracture morphology of the samples were observed by a scanning electron microscope(SEM).Also,the relative density,hardness and transverse rupture strength(TRS) of the sintered samples were *** results show that the samples prepared with a new epoxy resin-absolute ethanol system by the DIW process have high solid content of printing slurry,good surface roughness,high relative density and high *** solid content of the slurry suitable for DIW was 60 vol%,and the internal diameter of the nozzle was set to 0.4 mm,the printing speed was set to 30 mm·s^(-1),and the layer height was set to 0.36 *** the sample with 35 wt% TiC-316 L,the relative density,hardness and TRS of the sintered sample can reach 99.3%,HRA 79.5 and 1438 MPa,respectively.

关键词： DIW MMCs Epoxy resin TiC 316L