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Meng Qingsen Quan wanglin Cheng dajun Shen yanli

Effect of Electric Field on the Self-propagating High-temperature Synthesis of Functionally Gradient Materials. Meng Qingsen Quan wanglin Cheng dajun Shen yanli (Taiyuan University of Technology， Taiyuan 030024，China )

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Meng Qingsen Quan wanglin Cheng dajun Shen yanli

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  1. Effect of Electric Field on the Self-propagating High-temperature Synthesis of Functionally Gradient Materials Meng Qingsen Quan wanglin Cheng dajun Shen yanli (Taiyuan University of Technology， Taiyuan 030024，China ) Invitation for the 2nd German-Sino Workshop on EPM, Oct.16-19, 2005

  2. Self-propagating High-temperature Synthesis(SHS) SHS is a science-intensive process.Its comprehension requires erudition in thermodynamics, chemical kinetics, general and structural macrokinetics, materials science, and other allied fields of knowledge.

  3. Schema of SHS Fig.1. Schema of electric field activated synthesis reaction equipment

  4. Top Die Column Die Bottom Die Preparation method of gradient reagent PressureMachine (F) Gradient Reagent F

  5. Schema of SHS.

  6. testing number Fe% of 0.25(3Ni+Ti)+(1-0.25) (Ti+C) system testing number Fe% of 5Ti+3TiO2+3C+4Al A01 0% B01 0% A02 10% B02 10% A03 20% B03 20% A04 30% B04 30% A05 40% B05 40% A06 50% B06 50% A07 60% Scheme of Experiment Tab.1. Components list of single-layer reactants stocks.

  7. 5Ti+3TiO +3C+4Al+0 %Fe 2 5Ti+3TiO +3C+4Al+10 %Fe 2 5Ti+3TiO +3C+4Al+20 %Fe 2 Design of Gradient Reagent Ti+C+2 %Ni+0%Fe Fig.2 . Schematic diagram of the reactants stock of TiC-Ni-x%Fe system. Ti+C+25 %Ni+10 %Fe Ti+C+25 %Ni+20 %Fe Fig.3 . Schematic diagram of the reactants stock of TiC-Al2O3-x%Fe system.

  8. Models of Combution Front edge zone of reaction Zone of partly reaction Reagent Product Preheat zone Fig.5 . Combustion reaction model of the gradient layers reactants Fig. 4. Combustion wave model of quenching

  9. PreparedFGM Fig. 6. TiC-Ni-x%Fe system FGM prepared by SHS. Fig.7 . TiC-Al2O3-x%Fe system FGM prepared by SHS.

  10. Testing and Analytic technique • Microscopic structure Analysing （XJL-024、SEM LEO520） • Hardness Testing（M-400-Hi、HRBV-1875） • Phase composition Analysing（ Y-2000 ）

  11. c a 1mm b Microstructure Contrast between not imposed electric field and imposed electric field Fig.8. Microstructures of TiC-Ni-x%Fe system compounds prepared before and after imposed electric field. imposed electric field not imposed electric field

  12. 200μm 200μm 200μm Microstructure of FGM (TiC-Ni-x%Fe) a Fig. 9 . Microstructure of each gradient layer of TiC-Ni-x%Fe system 1 First Layer Second layer 5 Second layer First Layer Third Layer 100μm 4 2 6 b 3 Third Layer Second layer 1mm Fig. 10. microstructure of gradient layers of TiC-Ni-x%Fe system

  13. a d b c TiC Metal and intermetallic compound Fig. 11 . Microstructure and energy spectrum analysis of the second layer.

  14. a CPS 2θ(o) b CPS 2θ(o) Phase composition Analysing(TiC-Ni-x%Fe) First Layer Second Layer

  15. c CPS 2θ(o) Third Layer Fig. 12 . Results of X-ray diffraction patterns of TiC-Ni-x%Fe system FGM. (a,b,c)

  16. First Layer(TiC-Ni-0%Fe) Second Layer(TiC-Ni-10%Fe) Third Layer(TiC-Ni-20%Fe) Testing Number 1 2 3 4 5 6 Hardness(HV) 1268 987 1177 773 976 604.5 Hardness Testing (TiC-Ni-x%Fe) Tab.2 . The micro hardness distribution of TiC-Ni-x%Fe system. Fig.13. The hardness distribution regularity of TiC-Ni-x%Fe system FGM Hardness /HRC Thickness of product /mm

  17. Fig.14 . Profiles of temperature (T), conversion (η), and rate of heat release (φ) in the vicinity of an advancing reaction front with a thickness of δw Effect of electric field on SHS

  18. v / mm·s-1 Fe / % v / mm·s-1 E / V·cm-1 Effect of electric field on SHS Fig. 15 . Relationship between combustion wave velocity and Fe content I/A×10、U/V·cm-1 t/s Fig. 16. Curve of current and voltage with time Fig.17 . Dependence of the wave velocity on E

  19. Transmit Mechanism of Solid State Ion on Electric field

  20. Conclusions • (1) The heat of self-propagation reaction and electric field induced is the driving force of mass transferring, which promoted the generating of the product of Ni3Ti and Fe5C2. • (2) From Fig. 14. , the imposed electric field makes the ions and free electrons of metal move in greater speed, which impels the temperature of the system increasing and improve the plenitude of reaction and the uniformity of products by accelerating the diffusion speed of electrons and ions. • (3) From Fig. 16. , the field distribution on reactants and products makes high temperature in the front edge, which overcomes the thermodynamic limits of SHS and actuates the reaction to proceed, increases reaction speed. • (4)From Fig. 17. , it is shown that the velocity of the combustion wave is linearly proportional to magnitude of electric field.

  21. Requirement and Hope 1) It is essential to understand the effect of the electric fields on the processes parameters such as density, combustion temperature, burning velocity, extent of conversion, composition, structure, properties of SHS products, etc. 2) Additional experimental and theoretical studies should be carried out about the effect of the electric fields on product of FGM.

  22. Acknowledgement This project was financially supported by National Natural Science Fund of China (50375105) Natural Science Fund of Shanxi Province (20031051)

  23. Thanks for your Attention

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