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Effects of HIPing Pressure on Microstructures and Properties of TiAl Alloy

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Journal of Central South University 2000年第3期12卷 140-142页

作者： CHEN Jian-xun huang bai-yun ZHOU Ke-chao ZHENG Qing State Key Laboratory for Powder Metallurgy Central South UniversityChangsha 410083China

Blended elemental Ti 34%Al powders (mass fraction), containing 1.5%TiC, were hot isostatic pressed to prepare TiAl alloys. The effects of HIPing pressure on the sintered density, microstructure, constitutions phase were studied in details. The results show that the density of TiAl alloy increases repaidly with the increase of the HIPing pressure. At the same time, with the increase of pressure, the Ti 3Al phase in matrix disappears. TiC reacts with other substance, forming Ti 2AlC phase, which precipitates at grain boundaries. With the increase of hot isostatic pressing(HIPing) pressure, the shrinkage of the alloys increases, the fine spherical Ti 2AlC phase can meet together and forms a needle shape Ti 2AlC, and the amount of needle shaped Ti 2AlC phase increases. The composite material of TiAl containing C can be made easily by HIPing technology.

关键词： TiAl alloy hot isostatic pressing pressure microstructure carbide

Determination of Li+ solid diffusion coefficient in LiMn2O4 by CITT

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Journal of Central South University of Technology 2005年第Z1期12卷 1-4页

作者： TANG Xin-cun huang bai-yun HE Yue-hui School of Chemistry and Chemical Engineering Central South University Changsha 410083 China State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China

The capacity intermittent titration technique (CITT) was developed based on the ratio of potentio-charge capacity to galvano-charge capacity (RPG) method, to continuously determine the solid diffusion coefficient (D) of the intercalary species within insertion-host materials with a small voltage region. The linear equations of D vs the value of ratio of the potentio-charge capacity to the galvano-charge capacity (q) were given. By the CITT technique,the Li+ solid diffusion coefficients within LiMn2 O4 at different voltages were determined. The results show that the values of D varied from 3. 447× 10-9 to 7.60× 10-11 cm2/s in the voltage range of charge from 3.3 to 4.3 V as a function of voltage with "W" shape.

关键词： capacity titration technique Li+ solid diffusion coefficient LiMn2O4

Effects of milling and active surfactants on rheological behavior of powder injection molding feedstock

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中国有色金属学会会刊：英文版 2001年第2期11卷 196-199页

作者：范景莲黄伯云曲选辉 State Key Laboratory for Powder Metallurgy Central South University State Key Laboratory for Powder Metallurgy Central South University Changsha 410083 P.R.China

The effects of milling and active surfactants on the rheological behavior of powder injection molding feedstock were discussed. The feedstock consists of traditional compositional 90W 7Ni 3Fe powder mixture and a wax based polymer binder. Before mixing feedstock, the powder mixture was milled for different times in a QM 1 high energy ball mill. The viscosity of the feedstock was examined in a capillary rheometer. The rheological behavior was evaluated from viscosity data. The results show that the feedstock belongs to a pseudoplastic fluid, milling decreases viscosity of the feedstock and the sensitivity of viscosity to shear strain rate. The flowability, rheology and powder loading of this feedstock are improved by milling. Active surfactants such as stearic acid (SA) and di n octyl o phthalate (DOP) have great influences on the rheological properties of the feedstock. DOP improves the flowability and rheological stability of the feedstock further. [

关键词： milling active surfactant rheological behavior

Cerium enrichment on sinter skin of mischmetal doped WC-Co cemented carbide

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Journal of Central South University of Technology 2005年第Z1期12卷 5-8页

作者： ZHANG Li CHEN Shu XIONG Xiang-jun huang bai-yun ZHANG Chuan-fu State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China Changsha Mining and Metallurgy Research Institute Changsha 410012 China State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China School of Metallurgical Science and Engineering Central South University Changsha 410083 China

Rare earth-doped WC-Co cemented carbides with low carbon-containing level were prepared by adding mischmetal (mainly containing lanthanum and cerium) in the form of cobalt pre-alloyed powder during *** sintering, the sinter skin (exterior) was observed and analyzed by scanning electron microscopy(SEM)and energy disperse X-ray spectroscopy(EDXS). The results show that during the sintering process lanthanum and cerium are separated and cerium predominantly migrates towards the surface forming precipitates containing *** analysis and polarization of cerium atom caused by the strong interaction between cerium atoms and high energy carbon atoms were used in explaining the observed phenomenon.

关键词： hardmetal lanthanum cerium atom polarization thermoldynamics enrichment

Microstructure and properties of Al-Mg-(Sc, Zr) welded joint

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Journal of Central South University of Technology 2005年第Z1期12卷 23-27页

作者： JIANG Feng CHEN Su-li huang bai-yun YIN Zhi-min HE Yue-hui School of Materials Science and Engineering Central South University Changsha 410083 China State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China School of Materials Science and Engineering Central South University Changsha 410083 China State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China School of Materials Science and Engineering Central South University Changsha 410083 China State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China

Mechanical properties and microstructure of Al-Mg-(Sc, Zr) welded joint prepared by manual labor melt inert gas(MIG) welding method using Al-Mg and Al-Mg-Sc weld wire as filling materials were studied comparatively. The results show that the apparent recrystallization does not happen in heat-affected zone. It proves that Al-Mg(Sc,Zr) alloy has a high capability of resistance to welding heat-soften. Using Al-Mg-Sc welding wire as filling material can obviously refine the grains of weld seam and improve its strength. The layer of small equal-axe grains in fusion area improves the joint strength between welded metal and base metal. The coefficients of welded joints when Al-Mg-Sc and Al-Mg welding wire are used as filling material are greater than 0. 90, respectively. The yield strength of welded joints with Al-Mg welding wire is only 187 MPa, one is as high as 287 MPa with A1-Mg-Sc welding wire, thus the working strength of the welded unit is greatly improved.

关键词： Al-Mg-Sc alloy welding welding wire microstructure and properties of welded seam

金属纤维增强型摩擦材料与灰铸铁滑动摩擦性能

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中南大学学报（自然科学版） 2007年第4期38卷 583-588页

作者：苏堤黄伯云中南大学粉末冶金国家重点实验室湖南长沙410083

采用X射线衍射（XRD）和X射线能谱分析（EDAX）对分别使用低炭钢纤维、黄铜纤维和紫铜纤维增强的3种半金属摩擦材料与灰铸铁在不同温度下滑动摩擦形成的磨屑进行分析,并结合扫描电子显微镜（SEM）观察摩擦材料表面形貌,分析材料的磨损特... 详细信息

采用X射线衍射（XRD）和X射线能谱分析（EDAX）对分别使用低炭钢纤维、黄铜纤维和紫铜纤维增强的3种半金属摩擦材料与灰铸铁在不同温度下滑动摩擦形成的磨屑进行分析,并结合扫描电子显微镜（SEM）观察摩擦材料表面形貌,分析材料的磨损特性,并对黄铜纤维和紫铜纤维增强的摩擦材料磨屑成分进行对比分析。XRD结果表明,钢纤维增强体系的摩擦材料磨屑中的主要相是α-Fe,BaSO4,FeCr2O4（或Fe3O4,Fe2O3）;黄铜和紫铜纤维增强体系的磨屑中主要相除钢纤维体系中含有的相外,还含有Cu。EDAX分析的结果与X射线物相分析的基本一致,钢纤维增强材料磨屑中的Fe原子数分数达50%-60%,Cu,Ba,Ca和Al等元素的原子数分数为6%-10%。Fe原子含量均较高,在紫铜纤维增强的材料中其他元素的原子含量都比黄铜纤维增强的材料中的浓度低,说明紫铜纤维增强的摩擦材料的磨损比黄铜纤维增强的摩擦材料的小,填料不容易脱落,但紫铜纤维增强的摩擦材料对对偶造成的损伤较大。

关键词：摩擦磨损磨屑钢纤维铜纤维半金属摩擦材料

Influence of phase components of tungsten oxide on homogeneity of ultrafine tungsten powder

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中国有色金属学会会刊：英文版 2000年第3期10卷 421-423页

作者： LIAO Ji qiao(廖寄乔) ZOU Zhi qiang(邹志强) L Hai bo(吕海波) CHEN Shao yi(陈绍衣) huang bai yun(黄伯云) Cent S Univ Technol Natl Key Lab Powder Met Changsha 410083 Peoples R China

The influence of phase components of tungsten oxide on homogeneity of ultrafine tungsten powder by conventional hydrogen reduction techniques was studied. Results show that phase components of tungsten oxide play a crucial role on homogeneity of metal tungsten powder; ultrafine and homogeneous tungsten powder can be produced from oxides which consist of only one phase. Due to the different reduction rates (or different reduction paths) of oxide which comprises different phases, the multi phase components tungsten oxide leads to a fine but in homogeneous metal tungsten powder.

关键词： tungsten oxide phase components ultrafine tungsten powder homogeneity

Densification Mechanism of Warm Compaction and Powder Mixture Designing Rules

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Journal of Central South University 2000年第1期12卷 4-6页

作者： CAO Shun hua,huang bai yun,QU Xuan hui,YI Jian hong(State Key Laboratory for Powder Metallurgy, Central South University of Technology, Changsha 410083, China) State Key Laboratory for Powder Metallurgy Central South University of Technology Changsha China

By phenomenological analysis of warm compaction, it is found that, compared with the contribution of particle plastical deformation to densification of powder compact,the particle rearrangement is a dominant densification mechanism for powder warm compaction, and the plastical deformation of particles plays an important role in offering accommodating deformation for particle rearrangement and densifying powder compact at the final stage of *** order to attain density gain as high as possible during warm compaction, six rules for designing warm compacting powder mixtures were proposed in detail.

关键词： warm compaction densification mechanism powder mixture designing rule

Microstructural evolution of TiAl base alloy during three-stepped thermo-mechanical treatment

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Journal of Central South University of Technology 2001年第1期8卷 9-12页

作者： LIU Yong,LIU Feng xiao,huang bai yun,ZHOU Ke chao,ZHANG Chuan fu (State Key Lab for Powder Metallurgy, Central South University, Changsha 410083, China) State Key Lab for Powder Metallurgy Central South University Changsha China

A TiAl base alloy ingot with a height to diameter ratio of 2.2 was broken down by multiple step canned forging. The microstructures after every deformation and subsequent recrystallization were observed by optical microscopy. Results show that at the first step the reduction should be carefully controlled in case of double bulge and crack of the ingot. After the first annealing, recrystallization occurred at the deformed grain boundaries and inside the grain. The recrystallized microstructure is favorable for further deformation. After the second deformation and annealing, coarsening of the lamellae occurred and the microstructure became equiaxed. By the final deformation and subsequent recrystallization, the coarse lamellar colony can be refined to about 20 μm, and homogeneous microstructure was obtained from the ingot with a large initial height to diameter ratio.

关键词： TiAl base alloy hot forging microstructure