Scanning Electron Microscopy tools for material characterization

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Scanning Electron Microscopy tools

for material characterization

Focus on EBSD for characterisation of dislocation structures

Floriane Léaux (EN–MME–MM)

5th International Workshop on Mechanisms of Vacuum Arcs 02-04/09/2015

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Outline

1. Introduction • SEM* principle

• Response to incident electrons

2. Characterisation of dislocation structures

• EBSD*

• Link with dislocations

• Misorientation criterion

• Example (ferritic steel)

3. Conclusion • Microscopy at CERN for CLIC

• SEM-FIB*

*SEM: Scanning Electron Microscope

*EBSD: Electron BackScattered Diffraction *FIB: Focused Ion Beam

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Introduction

 SEM principle

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SEM principle, response to incident electrons 1. Introduction Ref: AMMRF Incident beam Sample Light (cathodoluminescence) Bremsstrahlung Secondary electrons Backscattered electrons Heat Elastically scattered electrons Transmitted electrons Specimen current Auger electrons

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Characterisation of dislocation

structures

 EBSD principle

 Link with dislocations

 Introduction of a misorientation criteria, example of KAM*  EBSD and TEM*, between complementarity and

substitution

 Case of a ferritic steel

*KAM:Kernel Average Misorientation *TEM:Transmission Electron Microscope

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Diffraction of back scattered electrons Following Bragg condition

Diffraction cones Kikuchi lines Diffraction pattern EBSD principle (1/2) 2. Dislocation structures Electron beam Sample Phosphor screen Camera Electron beam Screen Kikuchi lines Diffraction cones Cristal Diffracting planes Ref:[BAU10]

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EBSD principle (2/2) 2. Dislocation structures • Mapping: • Phase • Orientation • … Ref: [BAU10] Oxford Instruments

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Link with dislocations

2. Dislocation structures

Ref: [WRI11]

Influence of dislocations on the diffraction pattern

*_{GND : Geomatrically Necessary Dislocations}

*_{SSD: Statistically Stored Dislocations}

Perfect crystal GND* _SSD* Contrast and sharpness decrease Local misorientation  Rotation of the pattern Theoretical diffraction pattern

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Link with dislocations

Ref: [WRI11]

Influence of dislocations on the diffraction pattern

*_{GND : Geometrically Necessary Dislocations}

*_{SSD: Statistically Stored Dislocations}

Perfect crystal GND* _SSD*  Rotation of the pattern Theoretical diffraction pattern Local misorientation

LAGB : Low Angle Grain Boundaries

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Introduction of misorientation criteria

• Example of Kernel Average Misorientation (KAM)

2. Dislocation structures Local misorientation

Misorientation within a subgrain/grain

0,5° < DQ < Q_lim

Q_lim= 5° or more, 15° for a grain

Deformation gradient

Link with dislocation densities (GND)

 Link with plastic deformation

Grain boundary: Q > Q_lim

𝐾𝐴𝑀_𝑖 = 1 𝐾

𝑗=1 𝐾

ΔΘ_𝑖𝑗, ΔΘ_𝑖𝑗 < ΔΘ_𝑙𝑖𝑚 Misorientation average between

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EBSD and TEM

• Between complementarity and substitution

TEM

EBSD

+

Imaging mode  direct image of dislocation structures

+

Understand mechanisms

−

Limited to small scale

−

Destructive method Deformation mechanisms dislocation structure Link with plastic deformation Quantitativ e results

+

Assessment of dislocation densities

+

Quantitative and statistic results

+

Non destructive method (for small samples)

−

Influence of experimental parameters  comparative results

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Case of a ferritic steel (1/3)

Ref: [LEA12]

Low carbon ferritic steel

Subjected to cyclic deformation (LCF* fatigue tests)

Total strain control : 0.3% < De_t < 1.2%

*LCF: Low Cycle Fatigue

TEM KAM No deformation High deformation, De_t = 1.2% 0 1 2 3 4 5

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Case of a ferritic steel (2/3)

• Take into account the experimental effect

Define a reference state

Calculate a variation of KAM 2. Dislocation structures Ref: [LEA12] Δ𝐾𝐴𝑀 = 𝐾𝐴𝑀 − 𝐾𝐴𝑀𝑟𝑒𝑓 𝐾𝐴𝑀_𝑟𝑒𝑓 -40 0 40 80 120 160 200 0 0,2 0,4 0,6 0,8 1 D K A M ( %) Déformation plastique De p (%)

Evolution de la taille de cellule et du <KAM>

0.5S 0.4S 0.3S 0.7S 1.0S 1.2S 0 5 10 15 20 25 30 35 40 0 0,25 0,5 0,75 1 1,25 1,5 1,75 2 0.3% 0.4% 0.5% 0.7% 1.0% 1.2% F ré q u en c e ( %) KAM (°) De t =

Evolution of DKAM with De_p KAM distribution

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Case of a ferritic steel (2/3) 2. Dislocation structures Ref: [LEA12] -40 0 40 80 120 160 200 0 0,5 1 1,5 2 2,5 0 0,2 0,4 0,6 0,8 1 D K A M ( %) T a ill e mo y en n e d e c el lu le (µm ) Déformation plastique De p (%)

1.0S 1.2S 0.7S 0.7S 0.5S 0.4S 0.3S 0.4S MEB-EBSD

MET _{Very good fit between EBSD}

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Case of a ferritic steel (2/3) 2. Dislocation structures Ref: [LEA12] -40 0 40 80 120 160 200 0 0,5 1 1,5 2 2,5 0 0,2 0,4 0,6 0,8 1 D K A M ( %) T a ill e mo y en n e d e c el lu le (µm ) Déformation plastique De p (%)

1.0S 1.2S 0.7S 0.7S 0.5S 0.4S 0.3S 0.4S MEB-EBSD

MET _{Very good fit between EBSD}

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Case of a ferritic steel (3/3) Case of CC metal

Dislocation structure = cells

• What about copper?

• What about other dislocation arrangements? • …

Ref: [LEA12]

Dislocation  appearance of BD ???

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Conclusion

 Microscopy at CERN in the context of CLIC  BD* and FE* description

 Dislocation structure charaterisation of pure copper and link with BD occurency

 Prespective : SEM-FIB and the 3D nanoworld

*BD: Break Down *FE: Field Emission

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Microscopy at CERN in the context of CLIC

• BD and FE description

 Charaterisation and localisation of BD

Post-Mortem analysis

Ref: [PER14]

Ana Teresa PEREZ FONTENLA SEM images review on CLIC

structures after testing

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Microscopy at CERN in the context of CLIC

• Dislocation structure charaterisation of copper

3. Conclusion

 Introduction of dislocation structure into Cu-OFE

 TEM bibliography  cell structure

 Monotonic and fatigue tests + EBSD charaterisation

Enrique RODRIGUEZ CASTRO Identification of dislocations patterns in Cu-OFE for CLIC project by using EBSD

POSTER session

• Link with BD occurency

• DC spark system Ref: [ZHA05]

[JIA03]

After cyclic deformation

After tension until rupture (monotonic)

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Prespective : SEM-FIB

• SEM-FIB  SEM microscope equiped with a focused ion column Electron column Ion column Sample New signals  Secondary ions  Secondary electrons  STEM*

*STEM: Scanning Transmission Electron Microscopy

Preferential etching Nanomachining

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Prespective : SEM-FIB 3. Conclusion Milling  Cross-sections  3D tomography Ref: TESCAN

Preparation of the sample

Acquisistion: Milling and

imaging 3D reconstruction

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Prespective : SEM-FIB

• Beginning 2016

• New possibilities for CLIC accelerating RF structure:  Delicate preparation on selected area  Cross section  STEM images  …

Up to now: Top view

Prespective:

Cross-section / bulk view

EBSD, KAM

?

• CERN is actually acquiring a SEM-FIB

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Thank you

AMMRF: http://www.ammrf.org.au/myscope/.

[BAU10]: Baudin T., Analyse EBSD Principe et cartographies d’orientations, Techniques de l’Ingénieur, 2010,

M 4 138, 1–17.

[JIA03]: Jia W.P. and Fernandes J.V., Mechanical behaviour and the evolution of the dislocation structure of copper polycrystal deformed under fatigue-tension and tension-fatigue sequential strain paths, MSE A 348, 2003, 133-144.

[LEA12]: Léaux F., Relation entre microstructure et fatigue d’un acier ferritique utilise dans l’industrie

automobile: élaborationd’indicateurs d’endommagement, Science des matériaux: Université Lille 1 – Sciences et Technologies, 2012

[PER14]: A.T. Perez Fontenla, Post-Mortem analysisTD24 R05 N1 tested in X Box 1, CERN, EDMS:1450676, 2014

[WRI11]: Wright S.I., Nowell M.M. & Field D.P., A review of strain analysis using electron backscatter diffraction. Microscopy and microanalysis, 2011, vol.17, n°3,316–29.

[ZHA05]: Zhang J. and Jiang Y., An experimental investigation on cyclic plastic deformation and substructures of polycrystaline copper, Int. J. Of Plasticity 21, 2005, 2191-2211.