In-situ fabrication of functionally graded Al/Mg2Si by electromagnetic separation

1
In-situ fabrication of functionally graded
Al/Mg2Si by electromagnetic separation
2nd Sino-Germany Workshop on Electromagnetic
Processing of Materials

• Li Jianguo
• lijg_at_sjtu.edu.cn

School of Materials Science and Engineering,
Shanghai Jiaotong University, Shanghai 200030,
China
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Outline

• 1. Motivation
• 2. Principle of the process
• 3. Experiments and results
• 4. Summary

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Motivation

• The in-situ Al-Mg2Si composites have great
  potential applications in the automotive and
  aerospace industries due to their excellent
  properties.
• 1.ProblemsHard and fragile primary phases
  (eg. Mg2Si in Al-Mg-Si) may harmful to mechanical
  properties
• 2.SolutionGradient distributed from the
  surface to the centerFunctionally graded
  materials(FGMs).

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The process of FGMs by EMS

• The process of in-situ FGMs by
  electromagnetic separation (EMS) method is
  recently proposed by our laboratory. It produces
  the in-situ FGMs using usual casting under
  electromagnetic field by one-step. So it lower
  the production cost. And it can produce the
  thermodynamically stable systems by in-situ
  nucleation and growth of the reinforcing
  particles from the parent melt.

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Principle of the process
Principle of the process of in-situ FGMs by
Electromagnetic Separation method
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Movement analysis of particle

• Electromagnetic Archimedes force acting on a
  spherical primary particle can be written

(1)

• The buoyant force due to gravity imposed on the
  primary particle is stated as

(2)
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• The motion drag force of the primary particles
  in the molten metal is expressed as

(3)

• When these forces are in the balance

(4)

• The terminal migration velocity of primary
  particle as

(5)
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CD is the drag coefficient, which is related to
the Reynolds number . with
laminar flow,
( 6 )
And when the mode of the movement is transition
flow ,
( 7 )

• where v is the velocity of the primary particle
  and the viscosity of the melt.

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Experiments and results

• Equipments of experiment
• Effects of Element Ti
• Effects of process parameters

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Equipment
Schematic of equipments used in the process of
FGMs by EMS method ( a ) Top view of the
equipments, ( b ) Front view of the equipments.
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Effects of element Ti on Microstructures of
particle packed region
Process parameters Pouring temperature
850oC Mould temperature 400oC Electromagnetic
force 5104 N/m3
Composition Al-15Mg2Si 5Si
Composition Al-15Mg2Si 5Si-4Ti
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Microstructures at higher magnification of
Al-15Mg2Si 5Si-4Ti samples

• ß is Al3Ti
• d is a kind of Al-Si-Ti ternary intermetallic
  compounds, and composition is 65.12at.Al-13.47at
  .Si-21.41at.Ti

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Microstructures of in-situ Al/MgSi FGMs by EMS
Method

• Process parameters
• Pouring temperature 850oC
• Mould temperature of 400oC
• Electromagnetic force 5104 N/m3
• Composition Al-15Mg2Si 5Si-4Ti

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Effects of the electromagnetic force on particle
distributions
5104 N/m3
3104 N/m3
1104 N/m3
Microstructures of upper side in the samples
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Movement time of particles for unit distance
(1mm) vs the electromagnetic force
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Effects of mould temperature on particle
distribution
600oC
400oC
200oC
Microstructures of upper side in the samples
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Effects of pouring temperature on the particle
distributions
850oC
800oC
750oC
Microstructures of upper side in the samples
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Cooling curves of melt
Effects of mould temperature
Effects of Pouring temperature
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Effects of the composition on particle
distributions

• Al-15Mg2Si-5Si-4Ti

Al-20Mg2Si-5Si-3.75Ti
Al-25Mg2Si-5Si-3.5Ti
Microstructures of upper side in the samples
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Summary

• 1. In-situ Al/Mg2Si FGMs was successfully
  prepared by EMS method.
• 2. Additional element Ti can prevent primary
  Mg2Si particles from forming the particle
  clusters.
• 3. There exists a critical value of
  electromagnetic force, and the In-situ Al/Mg2Si
  FGMs can be prepared by EMS method only when the
  electromagnetic force is beyond it.
• 4. Increasing of the electromagnetic force
  and the content of Mg2Si and decreasing of the
  solidification rate can make the particle volume
  fraction of the particle packed region and the
  gradient of particle distributions increase.

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Acknowledgements

• The work is supported by the National
  Natural Science Foundation of China.
• We express our sincere thanks for their
  financial support.

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The end

• Thank you!