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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 School of Metallurgy Xi’an University of Architecture & Technology

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

APPLICABILITY OF THE MASS ACTION LAW IN COMBINATION WITH THE COEXISTENCE THEORY OF METALLIC MELTS INVOLVING COMPOUND TO BINARY METALLIC MELTS

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Acta Metallurgica Sinica(English Letters) 2002年第4期15卷 353-362页

作者： J.ZhangMetallurgical Engineering School, University of Science and Technology Beijing, Beijing 100083, China Manuscript received 9 March 2001 in revised form 7 August 2001 Metallurgical Engineering School University of Science and Technology Beijing Beijing 100083 China

Based on the atomicity and molecularity as well as the consistency ofthermodynamic properties and activities of metallic melts with their structures, the coexistencetheory of metallic melts structure involving compound has been suggested. According to this theory,the calculating models of mass action concentrations for different binary metallic melts have beenformulated. The calculated mass action concentrations agree well with corresponding measuredactivities, which confirms that the suggested theory can reflect the structural characteristics ofmetallic melts involving compound and that the mass action law is widely applicable to this kind ofmetallic melts.

关键词： metallic melts activity mass action law coexistence theory

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

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

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

Mold Filling Behavior of Melts with Different Viscosity under Centrifugal Force Field

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Journal of Materials Science & Technology 2002年第2期18卷 148-151页

作者： Daming XU, Qingmei YU, Xin LI and Geying ANSchool of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China [ Manuscript received October 12, 2001, in revised form december 10, 2001] Sch. of Mat. Sci. and Eng. Harbin Inst. of Technol. Harbin 150001 China

Recently proposed mathematical model for mold filling processes under centrifugal force field conditions and the computer codes were first tested through the sample simulation of gravity mold filling process for a benchmark plate-casting, which were compared with quoted experimental observations. The model and the developed computer program were then applied to the numerical simulation of centrifugal field mold filling processes for a thin-section casting with a titanium alloy melt of assumed viscosity of 1.2 and 12.0 mm2/s, respectively. The computation result comparison shows that the flow behaviors of the filling melts are basically similar to each other although the less viscous melt tends to fill into the thin section casting cavity faster.

关键词： Centrifugal casting Mold filling Viscosity Numerical simulation

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 Material and Metallurgy Engineering Kunming University of Science and Technology 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

ON THE TENSILE MECHANICAL PROPERTY OF Si-Mn TRIP STEELS AT HIGH STRAIN RATE

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Acta Metallurgica Sinica(English Letters) 2002年第3期15卷 285-294页

作者： X.C. Wei, L. Li, R.Y. Fu and W. ShiSchool of Materials Science and Engineering, Shanghai University, Shanghai 200072, China Manuscript received 18 June 2001 in revised form 7 November 2001 School of Materials Science and Engineering Shanghai University

Tensile mechanical properties of 1.6Si-1.58Mn-0.195C TRIP (transformation-induced plasticity) steels under high strain rate and effects of DP (dual-phase) treatments were studied and compared to the quasi-static tensile behavior. The results show that the increasing of strain rate leads to increasing in their strengths and decreasing in the uniform elongation remarkably. Because the stable retained austenite in TRIP steel can transform to martensite during tensile testing and the material exhibits excellent characteristic of transformation induced plasticity, the plastic deformation behavior is evidently improved and the combination of strength and elongation is superior to that of dual-phase steel, although its strength is smaller than that of DP steel. However, DP treated steel shown lower elongation under dynamic tension in spite of higher strength. A model was proposed to explain the excellent elongation rate of TRIP steel compared with DP steel on the basis of SEM analysis and the strength of the components in microstructure.

关键词： automobile sheet steel TRIP steel,high strain rate,tensile impact

EFFECT OF RESIDUAL STRESS ON THE MARTENSITIC TRANSformATION OF SPUTTER-DEPOSITED SMA THIN FILMS

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Acta Metallurgica Sinica(English Letters) 2002年第4期15卷 391-395页

作者： L.Wang,D.Xu and B.C.CaiInformation Storage Research Center, Shanghai Jiao Tong University, Shanghai 200030, China Manuscript received 14 September 2001 in revised form 27 November 2001 Information Storage Research Center Shanghai Jiao Tong University

TiNi thin films were sputter-deposited on circular single-crystal silicon substrates un-der various sputtering parameters. The crystal structure and residual stress of the as-deposited films were determined by X-ray diffraction and substrate-curvature method. The phenomenon of stress-suppressed martensitic transformation was observed. R is considered that the residual stresses in SMA thin films based on circular substrates act as balanced biaxial tensile stresses. The status of equilibrant delays the align-ment of self-accommodated variants and the volume shrinkage during the martensitic transformation.

关键词： martensitic transformation residual stress TiNi thin film shape memory alloy