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Acta Metallurgica Sinica(English Letters) 2002年第4期15卷 375-379页

作者： H.Yu,Y.L.Kang,H.B.Dong,D.L.Liu and J.FuUniversity of Science and Technology Beijing, Beijing 100083, China Manuscript received 10 October 2001 in revised form 25 january 2002 Univ. of Sci. and Technol. Beijing Beijing 100083 China

This paper investigated the mechanism of precipitation and its influence upon prop-erties of ultra-thin hot strips of low carbon steel produced by CSP techniques using experiment and thermodynamics theory. The experimental results show that there are lots of fine and dispersive precipitates in microstructures. By analysis, most of aluminum nitrides are in grains, while coexisted precipitates of MnS are along grain boundaries. Coexisted precipitates compose cation-vacancy type oxides such as Al2O3 in the core, while MnS is at the fringe of surface. The precipitation behavior of AIN and MnS in the hot strip is studied by thermodynamic calculation. At last, implica-tions between strengthening effect and techniques are analyzed using obtained solubility products.

关键词： CSP precipitation thermodynamics strengthening

INFLUENCE OF CARBON CONTENT OF MARTENSITE STEELS ON HARDNESS RE-DISTRIBUTION NEAR WORN SURFACE

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Acta Metallurgica Sinica(English Letters) 2002年第4期15卷 346-352页

作者： Y.P. MaSchool of Metallurgy, Xi’an University of Architecture & Technology, Xi’an 710055, China Manuscript received 5 November 2001 in revised form 30 january 2002 Sch. of Metall. Xi'an Univ. of Arch. and Technol. Xi'an 710055 China

After three-body abrasion, the hardness re-distribution near the worn surface has a close relationship with the carbon content of martensite steel. It is considered that there is a competition between the work-hardening and the temper softening, which results from deformation and friction heat of material. When the carbon content of martensite steel is below about 0.6%, the subsurface hardness distribution of material is a softened layer sandwiched between two hardened layers, but above 0.6%C, no softened region appears on the hardness re-distribution curve.

关键词： martensite three-body abrasion hardness re-distribution carbon content

NUMERICAL SIMULATION OF ATOMIZATION GAS FIELDS IN VARIOUS ATOMIZING PROCESSES

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Acta Metallurgica Sinica(English Letters) 2002年第3期15卷 279-284页

作者： F.Y. Cao, J.F. Sun, C.S. Cui, J. Shen and Q.C. LiNational Key Laboratory of Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001,ChinaManuscript received 10 December 2001 in revised form 31 january 2002 Harbin Inst. of Technol. Harbin 150001 China

A Computational Fluid Dynamics Software was used to calculate the atomizing gas fields generated by a self-designed atomizer and to analyze the effects of key atomizing variables such as gas pressure and protrusion length of delivery tube on the gas flow state at the tip of or inside the delivery tube. Increasing the length of delivery tube to a certain extent, the eddy flow region with positive pressure moves away from the tip of delivery tube, which is favorable to achieve the effective atomization of the melt.

关键词： atomization computational fluid dynamics numerical simulation powder metallurgy

Influence of Grain Boundary on Fatigue Behavior of Ni-base Bicrystals

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Journal of Materials Science & Technology 2002年第1期18卷 69-72页

作者： Jiansong WAN, Zhufeng YUE, Xiaoliang GENG and Zhixian LUDepartment of Engineering Mechanics, Northwestern Polytechnical University, Xi’an 710072, China [ Manuscript received january 16, 2001, in revised form April 27, 2001] Dept. of Eng. Mech. Northwestern Polytech. Univ. Xi'an 710072 China

The influence of the grain boundary on the fatigue behavior was studied by two three-point-bending (TPB) specimens. One TPB specimen was named Bicrystal 1, whose pre-crack was along the grain boundary and the applied load paralleled to pre-crack direction, while the other TPB specimen was named Bicrystal 2, whose the pre-crack was perpendicular to the grain boundary and the applied load paralleled also to the pre-crack. It was found that the rate of the fatigue crack growth of Bicrystal 1 was about a tenfold higher than that of Bicrystal 2. The fatigue behavior of Bicrystal 2 specimens was dependent on the distance between the crack tip and grain boundary. The crack growth rate was highest when the crack tip was at a critical distance to the grain boundary, while the rate was the lowest when the crack tip reached grain boundary. After the crack was over the grain boundary, the crack growth rate increased. The crystallographic finite element method was applied to analyze the stress and strain structure ahead of the crack, in order to reveal the above characteristics of the fatigue behavior. It is the grain boundary-induced redistribution of stresses near the crack tip that induces the difference of fatigue behavior.

关键词： Bicrystals Fatigue behavior Grain boundary Shielding effect

MODELING OF FERRITE GRAIN GROWTH OF LOW CARBON STEELS DURING HOT ROLLING

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Acta Metallurgica Sinica(English Letters) 2002年第3期15卷 267-271页

作者： Y.T. Zhang, D.Z. Li and Y.Y. LiInstitute of Metal Research, The Chinese Academy of Sciences, Shenyang 110016, China Manuscript received 26 December 2001 in revised form 9 February 2002 Inst. of Metal Res. Chinese Acad. of Sci. Shenyang 110016 China

For most commercial steels the prediction of the final properties depends on accurately calculating the room temperature ferrite grain size. A grain growth model is proposed for low carbon steels Q235B during hot rolling. By using this model, the initial ferrite grain size after continuous cooling and ferrite grain growing in coiling procedure can be predicted. In-plant trials were performed in the hot strip mill of Ansteel. The calculated final ferrite grain sizes are in good agreement with the experimental ones. It is helpful both for simulation of microstructure evolution and prediction of mechanical properties.

关键词： Ferrite Forecasting Grain growth Hot rolling Iron and steel plants Mathematical models Mechanical properties

Numerical Simulation of the TIG Welding Arc Behavior

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Journal of Materials Science & Technology 2002年第1期18卷 43-46页

作者： Chuansong WU and Jinqiang GAOInstitute of Materials Joining, Shandong University, Jinan 250061, China [ Manuscript received january 2, 2001, in revised form February 14, 2001] Inst. of Mat. Joining Shandong Univ. Jinan 250061 China

Achieving an effective utilization and exploitation of TIG welding arcs require a thorough understanding of the plasma properties and its physical processes. Through simultaneous solutions of the set of conservation equations for mass, momentum, energy and current, a mathematical model has been developed to predict the velocity, temperature, and current density distributions in argon welding arcs. The predicted temperature fields in arc regions, and the distribution of current density and heat flux at the anode agree well with measurements reported in literatures. This work could lay the foundation for developing a comprehensive model of the TIG welding process where a dynamic, two-way coupling between the welding arc and the weld pool surface is properly represented.

关键词： Welding Argon arc Plasma Behavior

Preparation and Properties of Sintering Additives Coated Si_3N_4 from Heterogeneous Nucleation Processing

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Journal of Materials Science & Technology 2002年第1期18卷 34-36页

作者： Juxian ZHANG, Jinjun FENG and Longqiao GAOBeijing Vacuum Electronics Research Institute, 100016 Beijing, China[ Manuscript received january 18, 2001, in revised form April 24, 2001] Beijing Vacuum Electron. Res. Inst. Beijing 100016 China

The sintering additives such as Al2O3 and/or Y2O3 were coated on the surfaces of Si3N4 particles via heterogeneous nucleation processing using a buffered pH solution as the precipitation reagent. They nucleated and grew only on the surfaces of Si3N4 and did not form sol particles in solution by TEM observation. The isoelectric point (IEP) of coated Si3N4 was different from that of as-received Si3N4. The IEP of AI(OH)3-coated Si3N4 occurred at pH8.4, which is close to that of alumina. When AI(OH)3-coated Si3N4 particles were coated with Y(OH)3, the IEP of coated Si3N4 powder shifted from pH8.4 to pH9.2, similar to that of yttria. In addition, the rheological data showed that Al2O3 and/or Y2O3 coated Si3N4 suspension is nearly Newtonian and that added Si3N4 suspension shows a shear rate thinning behavior.

关键词： Si3N4 powder Sintering additives Zeta potential Rheological property

Mechanism of the forming of Nodular Graphite

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Journal of Materials Science & Technology 2000年第6期16卷 615-618页

作者： Shoukui ZHANG (Dept. of Materials Engineering, Dalian University of Technology, Dalian 116024, China) [Manuscript received September 6, 1999, in revised form january 21, 2000] Dep. of Materials Eng. Dalian Univ. of Technol. Dalian 116024 China

This article presents a theory about the growth mechanism of bubble-screw dislocation of nodular graphite. Normally speaking, the crystallizing procedure of most nodular graphite is as follows: firstly, graphite generates nuclei on bubbles and fills them (mainly in the way of screw dislocation) forming the complete nuclei of nodular graphite-graphite bubble nuclei. Then, graphite grows up in the way of screw dislocation. Two important conditions concerning the production of nodular graphite are: (a) there is a relatively big interfacial energy between ferro liquid and graphite, and the one between ferro liquid and graphite prismatic plane is bigger than that between ferro liquid and graphite basal plane; (b) there are a certain amount of micro-bubbles in the melt.

关键词： Mechanism of the forming of Nodular Graphite

Pressure Effect on Crystallization of Zr_(55)Cu_(30)Al_(10)Ni_5 Bulk Metallic Glass

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Journal of Materials Science & Technology 2002年第2期18卷 184-186页

作者： Jianjun LIU, Keqiang QIU, Aimin WANG, Haifeng ZHANG, Bingzhe DING and Zhuangqi HUState Key Laboratory for RSA, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China [ Manuscript received February 16, 2001, in revised form May 25 Stat Key Lab. for RSA Inst. of Metal Res. Chinese Acad. of Sci. Shenyang 110016 China

The effect of pressure on the variation of the crystallization phases of the Zr55Cu30Al10Ni5 bulk glass and its thermal stability under high pressure annealing was investigated by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The mode of crystallization and products of crystallization of the Zr55Cu30Al10Ni5 bulk glass were quite different under different pressure. At ambient pressure, the crystallization products consisted of NiZr2 and CuZr2, while at pressure of 1 GPa and 3 GPa, the alloys crystallized into NiZr2 and Cu10Zr7, respectively. The alloy was nearly not crystallized and only a small amount of Cu10Zr7 was precipitated under 5 GPa. DSC proved that the mode of the crystallization under high pressure was different from that at ambient pressure.

关键词： Bulk metallic glan Pressure effect Crystallization

CATHODIC PROCESS AND WEAR RESISTANCE OF ELECTRO-DEPOSITED RE-Ni-W-P-SiC COMPOSITE COATING

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Acta Metallurgica Sinica(English Letters) 2002年第4期15卷 369-374页

作者： Z.C.Guo,X.Y.Zhu,R.D.Xu and X.W.YangFaculty of Material and Metallurgy Engineering, Kunming University of Science and Technology, Kunming650093, ChinaManuscript received 26 December 2001 in revised form 23 April 2002 Faculty of Mat. and Metall. Eng. Kunming Univ. of Sci. and Technol. Kunming 650093 China

Cathodic deposition current density of the composite coatings increases when SiC par-ticles and rare earth (RE) were added in the bath, which is profitable for Ni- W-P alloy to deposit in the cathod, forming Ni-W-P-SiC and RE-Ni-W-P-SiC composite coatings. On the contrary, the addition of PTFE in the bath decreases cathodic deposition current density of the coatings. The current density increases a little when the amount of RE is 7-9g/l; however, the current density increases greatly when the amount of RE is increased to 11-13g/l. Bui ij the amount of RE is raised further, the current density decreases. Hardness and wear resistance of RE-Ni-W-P-SiC composite coating have been studied, and the results show that the hardness and wear resistance of RE-Ni-W-P-SiC composite coating increase with increasing heat treatment tempera-ture, which reach peak values at 400℃; while the hardness and wear resistance of the coating decrease with the rise of heat treated temperature continuously.

关键词： electrodeposition RE-Ni-W-P-SiC composite coating cathodic process hardness and wear resistance