Dimpling: The Final Dimpling: The Final FrontierFrontier
It’s not just for golf balls and It’s not just for golf balls and grandmothers anymore!grandmothers anymore!Student: Jason BurbeyStudent: Jason Burbey
Faculty Advisor: Professor Eric StachFaculty Advisor: Professor Eric Stach
OutlineOutline
BackgroundBackground ObjectiveObjective Sample Preparation/CharacterizationSample Preparation/Characterization Sample Prep. InstrumentsSample Prep. Instruments Work CompletedWork Completed Future WorkFuture Work AcknowledgementsAcknowledgements QuestionsQuestions
BackgroundBackground Professor Ravi Professor Ravi
ChandranChandran• University of UtahUniversity of Utah
Laminated Steel and Laminated Steel and BrassBrass• Repeated cold rollingRepeated cold rolling• Continuation of Continuation of
previous studyprevious study Evaluated Mechanical Evaluated Mechanical
PropertiesProperties• Inverse relationship Inverse relationship
between yield strength between yield strength and bilayer thicknessand bilayer thickness
• Yield strengths as high Yield strengths as high as 850 MPa as 850 MPa
Why?Why?• Microstructural Microstructural
characterization neededcharacterization neededRavichandran, K. “Nanoscale Steel-Brass Multilayer Laminates Made By Cold Rolling: Microstructure and Tensile Properties.” Scripta Materialia Vol 42: 949,951
ObjectiveObjective
Microstructural Characterization of Microstructural Characterization of laminateslaminates• Bright Field Images in TEMBright Field Images in TEM
Features of interest:Features of interest:• Bilayer thicknessBilayer thickness• Interlamellar structureInterlamellar structure• Dislocation density and distributionDislocation density and distribution
Sample Sample Preparation/CharacterizationPreparation/Characterization
Dimple specimens to 10-15umDimple specimens to 10-15um
Ion Mill to produce very small hole in Ion Mill to produce very small hole in specimenspecimen• Electron TransparentElectron Transparent
Take bright-field images of specimen Take bright-field images of specimen using TEMusing TEM
The DimplerThe Dimpler
Model 2000 Model 2000 Sample Prep Sample Prep SystemSystem
Diamond Slurries Diamond Slurries and pastesand pastes• 6,3,1, .25 micron6,3,1, .25 micron
The Ion MillThe Ion Mill
Gatan Model 600 Gatan Model 600 Duo-MillDuo-Mill
ArAr++ ions directed at ions directed at specimen from specimen from both sides at a set both sides at a set angleangle
Fairly time Fairly time consumingconsuming
Transmission Electron MicroscopeTransmission Electron Microscope
JEOL Model 2000FXJEOL Model 2000FX Uses an Ultra High Uses an Ultra High
Vacuum (UHV)Vacuum (UHV)• 1010^-9 ^-9 -10-10^-11 ^-11 atmatm
Capable of high Capable of high resolution images resolution images at high at high magnificationsmagnifications• 1,000,000X or 1,000,000X or
higherhigher• Resolution of < 3ÅResolution of < 3Å
Work completedWork completed
Dimpled metallic laminatesDimpled metallic laminates• SS grinding wheelSS grinding wheel
Ion Mill attemptIon Mill attempt
• Micarta grinding WheelMicarta grinding Wheel Dimpled Ta/Si specimensDimpled Ta/Si specimens Dimpled InAs/GaP specimensDimpled InAs/GaP specimens
Metallic Laminates: SS grinding Metallic Laminates: SS grinding WheelWheel
Thicknesses varied from 90-Thicknesses varied from 90-290um290um
Used 3um slurry and Used 3um slurry and dimpled to 20umdimpled to 20um• Not all specimens were Not all specimens were
20um20um• Used optical microscope Used optical microscope
to check thicknessto check thickness• Re-dimpling difficultRe-dimpling difficult
Specimens 10-15um Specimens 10-15um achievedachieved• Ion Mill trialsIon Mill trials• InefficientInefficient
Start Over!Start Over!• Made more specimensMade more specimens• New dimpling progressionNew dimpling progression• Used different wheelUsed different wheel
Dimpling Laminates: Micarta Dimpling Laminates: Micarta Grinding WheelGrinding Wheel
Micarta Wheel is flatter Micarta Wheel is flatter and thicker than the SS and thicker than the SS grinding wheelgrinding wheel
Dimple the whole Dimple the whole specimen surfacespecimen surface• Used 6um slurryUsed 6um slurry• Sped up dimpling progressSped up dimpling progress
Much smoother surfaceMuch smoother surface• Very important for Ion Very important for Ion
MillingMilling Successful specimens Successful specimens
createdcreated• Stopped after 1um slurryStopped after 1um slurry• More scratches observed More scratches observed
with .25um pastewith .25um paste
Ta/Si SpecimensTa/Si Specimens
Checking phase Checking phase transformation of transformation of TaTa
Blue side = SiBlue side = Si Reflective = TaReflective = Ta Use diamond scribe Use diamond scribe
to cleave to cleave specimensspecimens
Sample PrepSample Prep Problem Problem Dimple on Si sideDimple on Si side
• SS grinding wheelSS grinding wheel Specimens thicker Specimens thicker
than laminatesthan laminates• 470-520um470-520um
Same progression Same progression as laminatesas laminates
Same force exerted Same force exerted by grinding armby grinding arm
Destruction of Destruction of specimensspecimens• Force too much Force too much • Si is fragile!Si is fragile!• Would crack at Would crack at
approx. 20umapprox. 20um
Solution for Ta/Si specimensSolution for Ta/Si specimens
Use less force!Use less force! Progressively Progressively
decrease forcedecrease force• Before switching Before switching
slurry/pasteslurry/paste 3 specimens from 3 specimens from
each bulk sample each bulk sample ready for Ion ready for Ion MillingMilling
In/As specimensIn/As specimens
Thicknesses between Thicknesses between 310-320um310-320um
Dimpled on GaP sideDimpled on GaP side• Used SS grinding wheelUsed SS grinding wheel• Same dimpling Same dimpling
progression as Ta/Siprogression as Ta/Si• Like butter!Like butter!• It smells…It smells…
3 specimens ready for 3 specimens ready for Ion MillingIon Milling
Future WorkFuture Work
Ion Mill all of the different specimensIon Mill all of the different specimens
Characterize specimens in TEM with Characterize specimens in TEM with help from Professor Stachhelp from Professor Stach
Publish characterization resultsPublish characterization results
AcknowledgementsAcknowledgements
Dr. KingDr. King Professor StachProfessor Stach Cheryl WallerCheryl Waller Vijay RawatVijay Rawat Rocco Cerchiara from FischioneRocco Cerchiara from Fischione Jan EberleJan Eberle MSE Dept.MSE Dept.
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