what is 3d ebsd? - chalmersfy.chalmers.se/~f10mh/halvarsson/em_intro_course_files/3d... · 2017....

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Three Dimensional Electron Backscatter Diffraction (3D-EBSD)

•  EBSD is usually a surface analysis technique – 2D •  3D EBSD involves a 3rd Dimension, with 2 variations:

A.  Analysis at different time intervals, showing the change of the microstructure through time: usually in combination with heating (or straining) experiments

B.  Analysis into the volume of the sample, by serial sectioning and reconstruction of the 3D microstructure

What is 3D EBSD?

Talk Outline

A.  Dynamic EBSD experiments in the SEM

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2004 Experiment: Starting Microstructure

Calcite sample. Data courtesy Sandra Piazolo, Stockholm University

2004 Experiment: Microstructure after a heat treatment

•  Single-phase Al-0.1%Mg alloy •  Deformed in channel die plane strain compression at 350°C to e=1.6 •  Sectioned in ND-RD plane •  Heated to ~280°C in FEGSEM •  EBSD Maps with prototype Oxford-Instruments NordlysF detector (~200

Hz): about 1.5 minutes per map •  EBSD maps at 10µm resolution obtained at intervals of ~15 mins

Heating Experiment Data

Images courtesy of Ian Brough & John Humphreys University of Manchester, UK

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500um

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500um

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EBSD in the FIB-SEM

•  Not a new technique – groups in the 1990s performed this manually to determine true boundary plane orientations (e.g. Prof. Randle, Swansea University)

•  In 2002-2004, several groups attempted this with a FIB-SEM. Alignment issues and poor resolution in z limited such experiments to c. 20 slices (and these took many days....)

•  In 2004 the first software for automated 3D EBSD in the FIB-SEM was developed

3D Serial Sectioning with EBSD

5µm

2-D dataset

Acknowledgement: Hans Mulders, FEI Company

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5µm

2-D dataset Reconstructed 3-D dataset


5µm

Visualization of slices in any orientation


Visualization of individual grains in 3-D


5µm

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Reconstructed 3-D dataset



5µm





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Quantitative grain information includes:

•  Volume •  Axial lengths of fitted

ellipsoids

•  Axial ratios of fitted ellipsoids

•  Shape orientation

•  Connectivity

•  Surface roughness •  Etc.

Grain size & shape analysis in 3-D

Data acquisition

Serial slicing & EBSD map acquisition

EBSD

e-

Ga+

Ion mill

Data

Data acquisition

Generally, milling is performed at 30kV and ~1-7 nA for acceptable pattern quality and milling

times, material and system dependent

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EBSD

e-

Serial slicing & EBSD map acquisition

Ga+

Ga+

Ga+

EBSD

Data

Data acquisition

Geometry of FIB-SEMs

FEI DB235 Ion column

Electron column

EBSD detector

Image courtesy Joe Michael, Sandia N.L.

Issue: Configuration of columns & camera

Complex stage motions necessary

e- ion+

EBSD


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180° rotation


Indent in Aluminium

Image series is very stable

�  90 slices over 18 µm – 200 nm /slice �  Maps 20 x 20 µm �  Total time ~26 hours

Shadowing of EBSD detector

It is important to remove enough extra material to the sides and

below the EBSD map area, otherwise severe shadowing can

occur.

Critical areas for material removal

EBSD map area

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Advantage: 3-D microstructural visualization & analysis �  Determination of true grain size and shape, in 3-D �  3D-EBSD makes full crystallographic characterization of interfaces

possible �  Morphology/topology of grains, e.g, for grain growth or phase

transformation studies

Limitations �  Small area of analysis (microns - tens of µm’s) �  Data collection time consuming �  Generally on the order of tens of hours to days

�  Material limitations: Susceptibility to FIB damage or alteration �  Destructive analysis �  Stability of the system over a very long period

3-D EBSD technical advantages & limitations

Applications examples

3-D EBSD applications example 2

Grain Sizes in a TRIP steel

FIB-SEM: FEI Nova600 DualBeam Slices: 62 (spacing 200nm) Step size: 100 nm Volume: ~ 3800 µm3 Acq. Time: 55 h (unattended) Total data: ~ 1.9 million analyses

Data courtesy of Dr. Ali Gholinia (HKL Technology)

Sample courtesy of of Dr. Roumen Petrov (Ghent University

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Reconstructed 3D orientation map

Reconstructed 3D orientation map showing individual slicing capability

Grain size comparison

Method Mean Grain Size (µm)

Maximum Grain Size (µm)

1D 0.8 2.4

2D 0.7 6.2

3D 0.8 8.1

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Other Potential Applications

•  Boundary analyses (e.g. twin boundary plane orientations in 3D)

•  Particle shape analyses •  Strain/stress fields •  Crack tip morphology in 3D •  ...

Overall Conclusions

•  Increasingly EBSD is used to analyse samples in 3 dimensions

•  This includes serial sectioning using a FIB-SEM and in-situ heating/straining/cooling experiments in the SEM

•  New generation fast EBSD detectors significantly boost this EBSD application field

what is 3d ebsd? - chalmersfy.chalmers.se/~f10mh/halvarsson/em_intro_course_files/3d... · 2017....

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