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
1
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.
2
3
Schema of SHS
Fig.1. Schema of electric field activated synthesis reaction
equipment
4
Preparation method of gradient reagent
Pressure Machine
(F)
Top Die
Gradient Reagent
Column Die
Bottom Die
F
5
Schema of SHS.
6
Scheme of Experiment
Tab.1. Components list of single-layer reactants stocks.
testing
number
Fe% of 0.25(3Ni+Ti)+(10.25) (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%
7
Design of Gradient Reagent
Ti+C+2 %Ni+0%Fe
Ti+C+25 %Ni+10%Fe
Ti+C+25 %Ni+20%Fe
Fig.2 . Schematic diagram of the reactants stock of TiC-Ni-x%Fe system.
5Ti+3TiO2 +3C+4Al+0%Fe
5Ti+3TiO2 +3C+4Al+10%Fe
5Ti+3TiO2 +3C+4Al+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
Product
Zone of
partly
reaction
Reagent
Preheat zone
Fig. 4. Combustion wave model
of quenching
Fig.5 . Combustion reaction model of
the gradient layers reactants
9
Prepared FGM
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、HRBV1875）
 Phase
composition Analysing（ Y-2000 ）
11
Microstructure Contrast between not imposed
electric field and imposed electric field
not imposed electric field
c
b
1mm
Fig.8. Microstructures of TiCNi-x%Fe system compounds
prepared
before and after imposed
electric field.
imposed electric field
a
12
Microstructure of FGM (TiC-Ni-x%Fe)
a
1
First
Layer
5
Second
layer
First
Layer
Second
layer
Third
Layer
100μm
4
2
6
3
b
Third
Layer
200μm
200μm
200μm
Second
layer
Fig. 9 . Microstructure of each
gradient layer of TiC-Ni-x%Fe
system
1mm
Fig. 10. microstructure of gradient
layers of TiC-Ni-x%Fe system
13
a
c
TiC
Metal and
intermetallic
compound
b
d
Fig. 11 . Microstructure and energy spectrum analysis of the second layer.
14
Phase composition Analysing
(TiC-Ni-x%Fe)
300
a
△
T iC
●Ni
△
200
CPS
Ni2T i
△
◇
△
◇
100
◇
0
20.00
△
◇
40.00
△
First Layer
●
60.00
80.00
2θ(o)
b
200
△
CPS
150
100
△
▲
◇
□
○
▲
TiC
○
□
FeNix
▲
Fe5C2
Ni
◇
Ni3 Ti
Second Layer
Fe
●
△
●
□
○
●
△
▲
50
0
20.00
△
40.00
60.00
2θ(o)
80.00
15
c
200
CPS
150
100
○
□
△
○
△
TiC
○Fe5C2
△
●
◇
○
□
◇
NixFe
▲Ni
□
Ni2Ti
●Fe
◇
Third Layer
△
●
▲
▲
▲
○
△
50
0
20.00
40.00
60.00
80.00
2θ(o)
Fig. 12 . Results of X-ray diffraction patterns of TiCNi-x%Fe system FGM. (a,b,c)
16
Hardness Testing (TiC-Ni-x%Fe)
Tab.2 . The micro hardness distribution of TiC-Ni-x%Fe system.
First Layer(TiC-Ni0%Fe)
Testing
Number
Hardness(HV)
Second Layer(TiC-Ni10%Fe)
Third Layer(TiCNi-20%Fe)
1
2
3
4
5
6
1268
987
1177
773
976
604.5
Fig.13. The hardness
distribution regularity of
TiC-Ni-x%Fe system
FGM
Hardness /HRC
100
78.6
80
75
74.3
72.1
66.4
60.7
60
52.9
40
20
第 3层
第 2层
T iC -Ni-10%F e T iC -Ni-20%F e
第 1层
T iC -Ni-0%F e
0
0
2
4
6
8
Thickness of product /mm
10
12
14
17
Effect of electric field on SHS
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
18
Effect of electric field on SHS
12
Fig. 15 . Relationship between combustion
wave velocity and Fe content
10
6
4
40
2
0
0
20
40
60
Fe / %
v / mm·s-1
30
I/A×10、U/V·cm-1
v / mm·s-1
8
电压V
电流I
30
S
E
20
V
10
0
1
2
3
t/s
4
5
6
20
Fig. 16. Curve of current and voltage
with time
10
0
0
10
20
E / V·cm-1
30
40
Fig.17 . Dependence of the wave velocity
on E
19
Transmit Mechanism of Solid State Ion on Electric field
E
Ni :  x : Ti 
NiTi x
E


Ti :  x : C : TiC x
Ni  xTi 
 NiTix
E
Ti  xC 
TiC X
E
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)
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Thanks for your Attention
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