5868 dan tatham
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8/8/2019 5868 Dan Tatham
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Microstructure evolutionMicrostructure evolution
during creep andduring creep andannealing of mineralsannealing of mineralsand rocksand rocks
Microstructure evolutionMicrostructure evolution
during creep andduring creep andannealing of mineralsannealing of mineralsand rocksand rocks
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D. Tatham,D.J. Prior, E. Mariani, S.J. Covey-Crump, J. Mecklenburgh, J. Wheeler
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High temperature deformation in the EarthHigh temperature deformation in the EarthHigh temperature deformation in the EarthHigh temperature deformation in the Earth
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Ed Garnero
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How do we gain insight into mechanisms of
deformation in the Earth’s crust and their implications?
SE NWTorre Saliere
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Fold structure in theFold structure in the MorcleMorcle NappeNappe,, SalanfeSalanfe, Swiss, SwissAlpsAlpsFold structure in theFold structure in the MorcleMorcle NappeNappe,, SalanfeSalanfe, Swiss, SwissAlpsAlps
1 Km
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Naturally deformed systems
Electronbackscatter
diffraction(EBSD)
Tools for understanding high temperatureTools for understanding high temperaturedeformation of rocksdeformation of rocks
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“Final microstrucutres ”
Experimental
rockdeformation
“Post mortem
analysis ”
Modelling
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These may tell us about:
•
We track microstructural evolutionthrough in-situ heating and deformationexperiments in the SEM with
simultaneous EBSD
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• the behaviour of special (twin, CSL) boundaries
• the control of orientation/chemistry on boundary migration
• what mechanisms control static and dynamic recrystallization
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The SEM in LiverpoolThe SEM in LiverpoolThe SEM in LiverpoolThe SEM in Liverpool
• The CamScan X500CrystalProbe is specificallydesigned for high-temperature in situ experiments.
• Tilted column permitsexperimentation on horizontal
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.
• Sample assembly anddetectors separated bywater-cooled heat shield,reducing contamination ofsignal at high experimentaltemperatures.
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Static Heating StageStatic Heating StageStatic Heating StageStatic Heating Stage
• Coiled Ta wire resistanceheater.
• Capable of furnace
temperatures in excess of1200oC.
• Equates to sample surfacetemperatures in excess of
o
7
.
• Samples up to 9x9x3mm sit ina cavity in graphite furnacecore.
• Furnace heating path controlled
by a Oxford InstrumentsIntelligent TemperatureController.
Seward et al., 2000 Scanning , 24, 232-240.
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Annealing of deformed NaClAnnealing of deformed NaClAnnealing of deformed NaClAnnealing of deformed NaCl
8Bestmann et al., 2005. J. Struct. Geol. 47, 447-457 Piazolo et al. 2006, Tectonophysics 427, 55-71
Slide8.avi
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Before heating
Annealing of deformed NaClAnnealing of deformed NaCl
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500 µµµµmBestmann et al., 2005. J. Struct. Geol. 47, 447-457
Piazolo et al. 2006, Tectonophysics 427, 55-71
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after 4.5h heating at 350-410°°°°C
Annealing of deformed NaClAnnealing of deformed NaCl
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500 µµµµm
Bestmann et al., 2005. J. Struct. Geol. 47, 447-457
Piazolo et al. 2006, Tectonophysics 427, 55-71
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GBM at low T GBM at high T
12 Piazolo et al., 2006, Tectonophysics 427, 55-71
Increasing length of straight segment movement
Increasing face control
Decreasing influence of pre-existing substructure
Decreasing tendency to create ‘poikiloblasts’
Increasing continuity (time and space) of movement
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Grain growth in annealed copper at 850Grain growth in annealed copper at 850ooCCGrain growth in annealed copper at 850Grain growth in annealed copper at 850ooCC
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Video is 30x real-time
Slide13.avi
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Grain growth in annealed copper at 850Grain growth in annealed copper at 850ooCCGrain growth in annealed copper at 850Grain growth in annealed copper at 850ooCC
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In In- -situ situ deformation & heating stagedeformation & heating stageIn In- -situ situ deformation & heating stagedeformation & heating stage
• Stepper motor-driven tensileheating/deformation rig in-situ in SEM.
• Opposing lead screws allowtensile load & strain whilekeeping the area of investigationunder the electron beam.
LVDTs
Load
cell
Steppermotor
Sample
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•
capable of furnacetemperatures in excess of1400oC & sample surfacetemperatures well in excess of1000oC.
• Samples thermally isolated fromdeformation assembly byceramic jig.
• Controlled via LabVIEW.
Water-cooled plate
HeatersCeramic sample jig
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Deformation in copper at ~700Deformation in copper at ~700ooCCDeformation in copper at ~700Deformation in copper at ~700ooCC
16Video is 300x real-time, 0.8mm total extension
Slide16.avi
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Pressure
• inhibits brittle failure
• promotes GBM
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In the SEM we need higher temperature but...
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Practicalities of working on geologically important materialsPracticalities of working on geologically important materials
20Mariani and Tatham, unpublished experiments; Bestmann. unpublished experiments
Slide20.avi
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LVDT
fixed piston
displacement rods
Tracking microstructure evolutionTracking microstructure evolution
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High T creep rig
(to Mariani, July 09)
New SEM stage
(to Prior, January 09) passive load
moving piston
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microstructural evolution
Tracking microstructure evolutionTracking microstructure evolution
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shear strain s t r e
s s
rheology
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U n d e f o r m e d
Tracking microstructure evolutionTracking microstructure evolution
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5 0 0 1 0 0 0
s c a l e / m s c a l e / m
00 5 0 0 1 0 0 0
shear strain = 0.5
T=973K
P = 3 0 0 M P a
With Julian Mecklenburgh,
Manchester
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Higher ResolutionHigher ResolutionHigher ResolutionHigher Resolution
Carrara marble
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Solenhofen limestone
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