April 8, 2004
Edward Barnard
Elizabeth Hager
Kevin McComber
Jenny Lichter
Outline
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Goal
Aluminum Mold and Initial Spin Tests
Silicone Mold
Ceramic Preform and Binders
High Temperature Pressure Vessel Calculations
Infiltration Time Calculations
Hardness Tests
SEM and Etching
Schedule
Goal
The goal of our project is to design a
manufacturing process to create a
selectively reinforced metal matrix
composite.
This project will take the theory
developed in Jess Wannasin’s thesis
work and scale up to part production.
Aluminum Mold
Centrifuge Setup
Initial Spin tests
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Small amount of Tin-Lead
Completed cleared out of runner
Silicone Mold
Polytek PLATSIL RTV
Silicone Rubber 71-10
Ceramic Preform
SiC 120 Grit
(100 µm particles)
Binder
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REMET R-25 binder (Prehydrolyzed Ethyl Silicate)
Silica
Compressive Strength (psi)
1200.00
No Sintering
Sintering for 1 hour
800.00
400.00
0.00
10
15
20
25
Binder Concentration (%)
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Other options: discuss acid phosphate binders with
Prof. Cima or look into epoxies
Wannasin
Pressure Vessel
1.5
2.0
0.50
0.125
Measurements in inches
High Temp. Pressure Vessel
Pmax
2
2
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 UTS ro  ri 
 2 2 
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S.F .  ro  ri 
Pmax = 730 psi = 50 atm
S. F. : safety factor = 2
Material
σUTS
rinner
router
router
S. F.
Aluminum
45 ksi
0.75
0.82
1.00
20
Aluminum
45 ksi 0.0625
0.0646
0.2425
60
But…. there’s a catch:
as the processing temperature increases, σUTS decreases
Wannasin
Tin-Lead Phase Diagram
http://cyberbuzz.gatech.edu/asm_tms/phase_diagrams/pd/sn_pb.gif
New Safety Factors
High Temp = 250 - 300°C
σUTS, High Temp = [0.2 – 0.3] * σUTS, Room Temp
σUTS  safety factor
Safety factors sufficient
rinner
S. F.
0.75
5
0.0625
15
Swagelok Catalog
Infiltration Time Calculations
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Darcy’s Law: pressure driven flow
L2 
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2kt
P
 (1  VP )
Tube-Bundle Theory with Blake-Kozeny equation
(1  VP )3
k 
4.2  S02  VP2
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L: infiltration length
Assumptions:
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Laminar flow
Particles are uniform spheres
k: Permeability
S0  6 DP
S0: surface area
Wannasin
Infiltration Time Calculations
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Values:  = 2* water, L = 4 inches,
DP = 100m
VP = 0.5 VP = 0.7
Threshold pressures 1.5 atm
Infiltration times
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3.5 atm
<<1 sec <<1 sec
P >> Pthreshold and infiltration times << 5 mins
Hardness Tests
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Preparation
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Cut samples with low-speed saw to obtain smooth
surface
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blade is material specific
part is a combination of materials of very different materials
Polished with 5-micron polishing paper
Results: used Rockwell B and H (low hardness)
Pure tin-lead: off-the-scale on the low end hardness
 MMC: on-scale but low
 MMC is harder than plain tin-lead 
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SEM
(Scanning Electron Microscopy)
Images
1mm
100m
SiC particles
500-600 microns
2mm
Fracture behavior
Etchers
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Ceramic particles not visible on all parts
Etching may be necessary
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cutting may have melted metal around ceramic
particles and obscured them from view
we’d like to see the particles so we can
characterize them with SEM
Further research into possible etchers
Projected Work Schedule
2/5 2/12 2/19 2/26 3/4 3/11 3/18 3/25 4/1 4/8 4/15 4/22 4/29 5/6 5/13
Materials
Metal choice
Ceramics choice
Part production
CAD
Alum. machined mold
Ceramic preform
Volume fraction
Size distribution
Time Permitting
"
Final testing
CODE:
Task
Sub-task
Gradation
Testing