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Nonlinear Theory on Dynamic Controlling Interface Patterns DuringSolidification of a Dilute Binary Alloy

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International Journal of Minerals,Metallurgy and materials 1999年第4期13卷 253-258页

作者： Zidong Wang Hanqi Hu(material science and engineering school, university of science and technology Beijing, Beijing 100083, China) material science and engineering school University of Science and Technology Beijing Beijing 100083 China

In non-equilibrium nonlinear region, the nonlinear equations of time dependence of perturbation amplitude at the solid/liquidinterface during solidification of a dilute binary alloy are established on the base of assuming that there is local equilibrium at the solid/liquid interface and considering that curvature, temperature and composition at the solid/liquid interface which are related to the perturbation amplitude are nonlinear. As a result, patterns at the solid/liquid interface during solidification process, which is from nonsteadystate to steady state can be controlled by these nonlinear equations.

关键词： nonlinearity solidification, dilute binary alloy, dynamic control

Relationship between Low Temperature Toughness and Microstructure in Low Activation Fe-Cr-Mn(W,V)Steel for Fusion Reactors

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International Journal of Minerals,Metallurgy and materials 1999年第2期13卷 111-115页

作者： Benfu Hu Chengchang jia(material science and engineering school, university of science and technology Beijing, Beijing 100083, China) material science and engineering school University of Science and Technology Beijing Beijing 100083 China

Fe-Cr-Mn (W, V) austenite steel was researched in order to supply a theory base for the first wall materials of fusion *** included vacuum melting, forging, annealing, solution treatment, Charpy impact tests and microstructure observation. Theresults show that the imped value decreases with the test temperature decreasing. In this system, there is ductile/brittle transition. Themechanism of this decrease of the impact value is considered to be due to γ - ε transformation in sub-stable austenite steel and stoppingoverlapping sacking fault by grain boundaries in stable austenite steel.

关键词： fusion reactor first wall materials low temperature toughness Fe-Cr-Mn system

Phenomenological Modeling of Warm Compaction and Experimental Verification

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International Journal of Minerals,Metallurgy and materials 2000年第4期14卷 292-295页

作者： Shiju Guo, Tao Lin (material science and engineering school, university of science and technology Beijing, Beijing 100083, China) material science and engineering school University of Science and Technology Beijing Beijing 100083 China

A phenomenological modeling approach to establishing the warm compaction equation and curves by modifying the regression equation of the room-temperature compaction curve is presented. An enhanced factor of compacting pressure is introduced into the equation in order to reveal the effects of powder/die temperature and filling height of powders on green density. Compaction curves yielded from this equation are consistent with the experimental data of ATOMET grade iron powders. The curves show that the powder/ die temperature should reduce as the filling heights of powders increase and that in some cases warm compaction can not give rise to a higher green density.

关键词： powder metallurgy warm compaction compaction equation materials

Annealing Texture Evolution of Ti-IF Steel during Batch Annealing

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International Journal of Minerals,Metallurgy and materials 1998年第3期12卷 175-179页

作者： Jing Shi Xianjin Wang(material science and engineering school, university of science and technology Beijing, Beijing 100083, China) material science and engineering school University of Science and Technology Beijing Beijing 100083 China

Texture development and recrystallization behavior of Ti-IF steel during Batch Annealing (BA) were investigared with X-ray diffraction and EBSP in lab, and the results were compared with research work on continu ous annealing (CA) with rapid heating rate. The basic tendencies are similar that eary nucleation takes place in ND fibers, RD fibers are consumed at the end of recrystallization, and ND texture dominates over annealing texture. However, the detailed texture transformation during batch annealing is different and somewhat more compicated than tha in rapid-heating process. Moreover, misorientation plays an important role in texture transformation of BA In addition, the results of EBSP are consistent with that of ODF well.

关键词： Ti-IF steel texture batch annealing X-ray diffraction EBSP

High-temperature oxidation behavior of Al_2O_3/TiAl matrix composite in air

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science China(Technological sciences) 2009年第5期52卷 1273-1282页

作者： AI TaoTao1,WANG Fen2 & FENG XiaoMing1 1 Department of materials science and engineering,shaanxi university of technology,hanzhong 72.003,China 2 school of materials science and engineering,shaanxi university of science and technology,Xi’an 710021,China Department of materials science and engineering Shaanxi University of Technology Hanzhong China school of materials science and engineering Shaanxi University of Science and Technology Xi’an China

The oxidation behavior of Al2O3/TiAl in situ composites fabricated by hot-pressing technology was in-vestigated at 900℃ in static *** results indicate that the mass gains of the composites samples decrease gradually with increasing Nb2O5 content and the inert Al2O3 dispersoids effectively increase the oxidation resistance of the *** higher the Al2O3 dispersoids content,the more pro-nounced the *** primary oxidation precesses obey approximately the linear laws,and the cyclic oxidation precesses follow the parabolic *** oxidized sample containing Ti2AlN and TiAl phases in the scales exhibits excellent oxidation *** oxide scale formed after exposure at 900 ℃ for 120 h is multiple-layered,consisting mainly of an outer TiO2 layer,an intermediate Al2O3 layer,and an inner TiO2+Al2O3 mixed *** the outer layer to the inner layer,TiO2+Al2O3 mixed layer presents the transit of Al-rich oxide to Ti-rich oxide mixed *** the substrate,cross-section micrograph shows a relatively loose layer,and micro-and macro-pores remain on this layer,which is a transition layer and transferres from Al2O3+TiO2 scale to *** thickness of oxide layer is about 20 μ*** is also found that continuous protective alumina scales can not be observed on the surface of oxida-tion *** ions diffuse outwardly to form the outer TiO2 layer,while oxygen ions transport inwardly to form the inner TiO2+Al2O3 mixed *** long-time intensive oxidation exposure,the internal Al2O3 scale has a good adhesiveness with the outer TiO2 *** obvious spallation of the oxide scales *** increased oxidation resistance by the presence of in situ Al2O3 particulates is at-tributed to the enhanced alumina-forming tendency and thin and dense scale ***2O3 particu-lates enhance the potential barrier of Ti ions from M/MO interface to O/MO interface,thereby the TiO2 growth rate decreases,which is also beneficial to improve the oxidation resistance.

关键词： Al2O3/TiAl matrix composite oxidation resistance high temperature

Microstructure Evolution of Semi-solid Processed Hyper-eutectic Al-30%Si Alloy

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International Journal of Minerals,Metallurgy and materials 1999年第4期13卷 259-261页

作者： Yanjun Li Weimin Mao Xueyou Zhong(material science and engineering school, university of science and technology Beijing, Beijing 100083, China) material science and engineering school University of Science and Technology Beijing Beijing 100083 China

An investigation was made on the influences of mechanical stirring on microstructure of hyper-eutectic Al-30%Si alloy (inmass fraction) during solidification. The primary Si crystals formed in the alloy melt were gradually changed from elongated platelets tonear-spherical shapes by mechanical stirring. The spheroidization of primary St crystals occurs by the mechanism of bending and fractureof Si platelets, wear and collision between Si crystals, and coalescence of small Si particles. The influence of under-cooling and coolingrate of the alloy melt on primary Si crystals of semi-solid processed alloys is investigated as well. The increase of under-cooling andcooling rate decreases the size of primary Si crystals.

关键词： semi-solid state process solidification structure mechanical stirring hyper-eutectic Al-Si alloy

A New Process for Preparing Fine-ceramic-containing Composite Coatings──Flame Spray Synthesis

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International Journal of Minerals,Metallurgy and materials 2000年第3期14卷 214-217页

作者： Changsong Liu, Jihua Huang, Sheng Yin (material science and engineering school, university of science and technology Beijing, Beijing 100083, China) material science and engineering school University of Science and Technology Beijing Beijing 100083 China

Flame spray synthesis (FSS), a combination of the flame spray technology and Self-propagation High-temperature Synthesis (SHS) was developed for preparing fine-ceramic-containing composite coatings. It can simplify the preparations of powder to synthesize and deposit the desired materials in one step. The preliminary results obtained from TiC-Fe cermet coatings by FSS process are reported. The peculiar microstructure of the composite coatings, which contains very fine (3GPa) and TiC-poor layers (Hv=3.0 -6.0GPa), is expected to play an important role in their tribological properties.

关键词： Self-propagation High-temperature Synthesis (SHS) flame spray flame spray synthesis (FSS) TiC-Fe cermet coating

Nickel multilayers and their effects on bend fatigue strength of leads

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Rare Metals 2004年第2期23卷 157-160页

作者： LIU Feihua WANG Zhanhua SHEN Zhuoshen school of material science and engineering, university of science and technology Beijing, Beijing 100083, China school of material science and engineering University of Science and Technology Beijing 北京 100083

Nickel is commonly coated on the outer leads for T8 metal package. The leadselectrodeposited by conventional dull or bright nickel over 5μm at direct current from Watt bathare hard to pass the bend fatigue test for three times. Nickel electrodeposited at multi waveformcurrent including direct current, single and double pulse from sulfamate bath can improve the bendfatigue strength of leads. Such nickel plating has a multilayer structure, its morphology ofsublayers can be clearly seen in its cross section with SEM. The electrochemical study shows thatthese sublayers have different corrosion potentials. The bend fatigue test of leads with suchplating for T8 metal package shows that the number of bend increases with the decrease of averagecurrent density of multi waveform, which can be attributed to the reduction of every sublayerthickness and the increase of layer numbers under the same condition of total thickness.

关键词： electroplating nickel multilayers multi waveform current bend fatiguestrength corrosion potential metal package

SEM in-situ Fatigue Observation on Crack Initiation and Growth from Inclusion in P/M Rene95 Superalloy

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Journal of university of science and technology Beijing 2001年第3期8卷 195-197页

作者： Lina Zhang, Jianxin Dong, Xishan Xie material science and engineering school, university of science and technology Beijing, Beijing 100083, China material science and Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

A special designed experiment was conducted for observing crack initiation and growth in P/M Rene95 superalloy under tension-tension loading by self-made SEM in-situ fatigue loading stag. Several alumina inclusion particles exposed at the specimen surface were observed carefully. During fatigue test inclusions led to cracks initiation. The cracks can be formed by two mechanisms. Generally, the cracks nucleated at the interface between inclusion and matrix. Sometimes, cracks were also formed inside the inclusion. As the increase of cycles, some cracks at the interface between inclusion and matrix broadened and propagated along the direction about 45 degrees to the loading axis. On the other hand, the cracks inside the inclusion propagated in the inclusion and towards matrix.

关键词： inclusion P/M superalloy LCF SEM in-situ fatigue