Fabrication of Mo/Cu Functional Gradient Material
by Hot-Explosive Consolidation
Pengwan Chena,*, Xiang Gaoa, Weiping Shenb, Zhiming Jianga, Sanxi Yuana, Qiang zhoua
aState
Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology,
Beijing 100081, China
bUniversity of Science and Technology Beijing, Beijing 100083, China
e-mail: pwchen@bit.edu.cn
Outline

Introduction

Hot-explosive consolidation apparatus

Preheating by self-propagating high-temperature
synthesis (SHS)

Experiment and characterization

Conclusions
Introduction
Functional gradient material (FGM) is a new kind of nonhomogeneous composite
Mo(W)/Cu FGM combines the advantages of molybdenum and copper
Powder metallurgy and hot isostatic pressing etc are traditional fabrication techniques
of Mo(W)/Cu functional gradient materials
Explosive consolidation provides a solution to fabricate high quality Mo/Cu FGM
Hot-explosive consolidation apparatus
1. Detonator; 2. Explosive lens; 3. Water； 4. Protection tube； 5. Tungsten wire； 6. Mo/Cu FGM sample；
7. Copper sample box；8. Steel plate；9. SHS powders；10. Sand
Experiment and characterization
Design and fabrication of pre-compacted Mo/Cu FGM sample
 The average particle sizes of Mo powder and Cu powder were 3 µm and 74 µm, respectively
 The first layer contained only Mo with a thickness of 3 mm
 The seventh layer contained only Cu with a thickness of 2 mm.
 The other five gradient layers contained different ratios of Mo and Cu with a thickness of 1 mm for each layer.
Composition of Mo/Cu FGM
Preheating by self-propagating hightemperature synthesis (SHS)
Self-propagating high-temperature synthesis(SHS) reaction was required to proceed
in a confined small space during explosive consolidation
A combined SHS system of (TiO2+Al+C) and (Fe2O3+ Al) were used to preheat the
pre-compacted Mo/Cu FGM sample
The mass ratio of (TiO2+Al+C) to (Fe2O3+Al) is 60%: 40%~80%: 20%.
 The pre-compacted Mo/Cu FGM sample can be preheated rapidly to 300℃~1000℃
in a small space by regulating the mass ratio of (TiO2+Al+C) to (Fe2O3+Al).
Typical temperature rise curves in FGM powder and water
Experiment and characterization
Shock wave propagation and shock pressure measurement
 The propagation and interaction of shock waves during explosive consolidation
were studied with flash X-ray cineradiography
 The shock pressures during the passage of shock waves were measured by manganin pressure gauges.
 MODEL1200-type flash X-ray camera system of Swedish Scandiflash AB Company
 Two space-time associated flash X-ray high-speed cameras
 The angle between two camera axis was 30°~45°
B
爆炸洞壁
爆炸中心
底片A
X射线脉冲发生器
底片B
A
防护窗口
The shock pressure histories at different locations during explosive consolidation
were recorded by the embedded manganin pressure gauges
Results of shock wave peak pressures
Densities and thickness of gradient layers of Mo/Cu FGM
Microstructure of Mo/Cu FGM:
(a) FGM-7 (Cu)/FGM-6; (b) FGM-6/FGM-5; (c) FGM-5/FGM-4;
(d) FGM-4/FGM-3; (e) FGM-3/FGM-2; (f) FGM-2/FGM-1 (Mo)
220
6.0
200
5.5
/105Scm-1
HV/× 10MPa
180
160
140
5.0
4.5
4.0
3.5
120
3.0
100
2.5
2.0
80
1.5
0
10
20
30
40
50
60
70
80
90 100
Cu content, V％
Hardness as a function of Cu content of gradient layers
0
10
20
30
40
50
60
70
80
90
100
Cu/V％
Electrical conductivity curve of Mo/Cu FGM
Thermal conductivity of FGM-3 & FGM-4 layer
  c 
p
Shear fracture surface morphology of FGM-1/FGM-2:
(a) SEI of fracture surface; (b) backscattered image of fracture surface;
(c) composition analysis image of Mo in (b); (d) composition analysis image of Cu in (b)
Conclusions
The symmetry and planeness of the bidirectional shock waves generated by the
explosive consolidation assembly are fairly good.
The pre-compacted Mo/Cu FGM sample can be preheated rapidly to 300℃~1000℃
in a confined small space by the exothermic reaction of self-propagating high
temperature synthesis.
The average relative density in the consolidated FGM can reach 95%
For refractory molybdenum, plastic flow and volume diffusion mechanism may be
dominant for the lack of liquid phase during sintering.
For copper rich layer, viscous flow may be the major sintering mechanism as its
relatively low melting point and good plasticity.
Thank you very much!