检索结果-南通市图书馆

Effect of inclusion size on the high cycle fatigue strength and failure mode of a high V alloyed powder metallurgy tool steel

在线全文

学校读者我要写书评

暂无评论

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

在线全文

学校读者我要写书评

暂无评论

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

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

在线全文

学校读者我要写书评

暂无评论

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

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

在线全文

学校读者我要写书评

暂无评论

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

在线全文

学校读者我要写书评

暂无评论

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.

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

在线全文

学校读者我要写书评

暂无评论

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

Carbothermal synthesis of Si_3N_4 powders using a combustion synthesis precursor

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2013年第1期20卷 76-81页

作者： Ai-min Chu Ming-li Qin Bao-rui Jia hui-feng Lu xuan-hui qu Beijing Key Laboratory for Advanced Powder Metallurgy and Particulate Materials School of Materials Science and Engineering University of Science and Technology Beijing School of Electro-mechanism Engineering Hunan University of Science and Technology

Si3N4 powders were synthesized by a carbothermal reduction method using a SiO2 ＋ C combustion synthesis precur- sor derived from a mixed solution consisting of silicic acid （Si source）, polyacrylamide （additive）, nitric acid （oxidizer）, urea （fuel）, and glucose （C source）. Scanning electron microscopy （SEM） micrographs showed that the obtained precursor exhibited a uniform mixture of SiO2 ＋ C composed of porous blocky particles up to -20 μm. The precursor was subsequently calcined under nitrogen at 1200-1550℃ for 2 h. X-ray diffraction （XRD） analysis revealed that the initial reduction reaction started at about 1300℃, and the complete transition of SiQ into Si3N4 was found at 1550℃. The Si3N4 powders, synthesized at 1550℃, exhibit a mixture phase of α- and -Si3N4 and consist of mainly agglomerates of fine particles of 100-300 nm, needle-like crystals and whiskers with a diameter of about 100 nm and a length up to several micrometers, and a minor amount of irregular-shaped growths.

关键词： silicon nitride powders carbothermal reduction combustion synthesis

Fabrication and sintering behavior of high-nitrogen nickel-free stainless steels by metal injection molding

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2010年第4期17卷 423-428页

作者： Zi-wei Xu Cheng-chang Jia Chun-jiang Kuang xuan-hui qu School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Powder Metallurgy Division Advanced Technology ＆ Materials Co. Ltd. Beijing 100081 China

High-nitrogen nickel-free stainless steels were fabricated by the metal injection molding technique using high nitrogen alloying powders and a mixture of three polymers as *** of metal powders and binders with various proportions were also investigated, and an optimum powder loading capacity was determined as 64vol%.Intact injection molded compacts were successfully obtained by regulating the processing *** debinding process for molded compacts was optimized with a combination of thermo-gravimetric analysis and differential scanning calorimetry *** optimum relative density and nitrogen content of the specimens are obtained at 1360℃,which are 97.8%and 0.79wt%,respectively.

关键词： metal injection molding debinding stainless steel sintering behavior sintered density nitrogen content

Effect of sintering on the relative density of Cr-coated diamond/Cu composites prepared by spark plasma sintering

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2016年第6期23卷 716-722页

作者： Wei Cui 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 State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

Cr-coated diamond/Cu composites were prepared by spark plasma sintering. The effects of sintering pressure, sintering temperature, sintering duration, and Cu powder particle size on the relative density and thermal conductivity of the composites were investigated in this paper. The influence of these parameters on the properties and microstructures of the composites was also discussed. The results show that the relative density of Cr-coated diamond/Cu reaches ~100% when the composite is gradually compressed to 30 MPa during the heating process. The densification temperature increases from 880 to 915℃ when the diamond content is increased from 45vol% to 60vol%. The densification temperature does not increase further when the content reaches 65vol%. Cu powder particles in larger size are beneficial for increasing the relative density of the composite.

关键词： metal matrix composites copper diamond relative density spark plasma sintering