Microstructural Characterization Microstructural Characterization

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Microstructural Characterization Microstructural Characterization

of of

Materials Materials

Eun Eun Soo Soo Park Park

Office: 33-316

Telephone: 880-7221

Email: espark@snu.ac.kr

Office hours: by an appointment

2009 spring

06. 03. 2009

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Content for previous class

Selected area diffraction Dark field image

Analysis for Ring pattern and Spot pattern kikuchi pattern

Mechanisms of image formation: contrast

Mass-thickness contrast Diffraction contrast

(major image formation mechanisms)

Phase contrast

(high resolution image of crystal lattice)

Z contrast imaging

(Dark field-STEM)

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Mass-thickness contrast

bright

dark

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Diffraction contrast (major image formation mechanisms)

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Phase contrast

(high resolution image of crystal lattice)

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Fast Fourier Transformation

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( STEM )

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piezoelectric

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Cowley (1969): for the same lenses, apertures and system dimension

the image contrast must be the same for CTEM and STEM

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56

20

38

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32

14

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Gd

₃₀

Ti

₂₅

Al

₂₅

Co

₂₀

100 nm

Gd

₃₀

Ti

₂₅

Al

₂₅

Cu

₂₀

Gd-Cu Ti

50 nm

Gd-Al Ti-Co

Gd

₃₀

Ti

₂₅

Al

₂₅

Ni

₂₀

100 nm

Ti Gd

0 10 20 30 40 50 60 70 80 90 100

1) Droplet structure

in Gd-Ti-Al-(Co, Ni, Cu) alloy system

400 600 800 1000 1200

Composition (%)

Temp. (K)

Ti

-38

-22 +15

-30

-28 -19

Gd Al

Co

* unpublished (2006)

Phase separation

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50 nm

Gd

₃₀

Zr

₂₅

Al

₂₅

Co

₂₀

50 nm

Gd

₃₀

Zr

₂₅

Al

₂₅

Cu

₂₀

Gd

₃₀

Zr

₂₅

Al

₂₅

Ni

₂₀

0 10 20 30 40 50 60 70 80 90 100

400 600 800 1000 1200

Composition (%)

Temp. (K)

Zr

-38

-22 +9

-44

-41 -19

Gd Al

Co

2) Interconnected structure

in Gd-Zr-Al-(Co, Ni, Cu) alloy system

* unpublished (2006)

Phase separation

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2 nm

① ②

①

②

Gd ₃₀ Zr ₂₅ Al ₂₅ Co ₂₀ * unpublished (2008)

Nano scale (<3 mm) interconnected Phase separation

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0 5 10 15 20 25 30 35

1 2 3 4 5 6 7 8 9 10

Z r G d

Spectrum Al Co Zr Gd

Spectrum(1) 23.16 30.79 18.34 27.70 Spectrum(2) 22.74 33.40 17.74 26.12 Spectrum(3) 24.15 30.38 23.29 22.18 Spectrum(4) 21.48 31.52 22.31 24.69 Spectrum(5) 22.45 37.20 15.46 24.89 Spectrum(6) 27.20 24.83 20.24 27.74 Spectrum(7) 23.67 24.90 18.47 32.96 Spectrum(8) 22.47 34.47 23.44 19.62 Spectrum(9) 26.01 26.16 25.50 22.33 Spectrum(10) 17.90 44.35 25.05 12.70

Chemical fluctuation - EDS Chemical fluctuation - EDS

10 nm Beam size : 0.7 nm

Distance between spots : ~ 5 nm

Spectrum Ni Nb

Spectrum(1) 65.22 34.78 Spectrum(2) 64.84 35.16 Spectrum(3) 66.66 33.34 Spectrum(4) 67.23 32.77 Spectrum(5) 67.57 32.43 Spectrum(6) 69.42 30.58 Spectrum(7) 66.98 33.02

Beam size : 0.7 nm

Distance between spots : ~ 15 nm

30 35 40 45 50 55 60 65 70

1 2 3 4 5 6 7

Ni Nb

Gd

₃₀

Zr

₂₅

Al

₂₅

Co

₂₀

Ni

₆₀

Nb

₄₀

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Chemical fluctuation – Z contrast Chemical fluctuation – Z contrast

nm scale contrast fluctuation in Z contrast image

⇒ early stage in spinodal decomposition

10 nm 10 nm

STEM BF

10 nm

STEM DF STEM DF

10 nm

10 nm 1 nm

STEM BF STEM DF STEM DF

Gd

₃₀

Zr

₂₅

Al

₂₅

Co

₂₀

Ni

₆₀

Nb

₄₀

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In-situ capabilities

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9 mm 11.5 mm

2.5 mm

11.5 mm

9 mm

EXAMPLE: Preparation of specimen for in-situ tensile test

시편 종류

: Ti

₄₀

Zr

₂₉

Cu

₉

Ni

₈

Be

₁₄

ribbon monolithic / crystallization of 4 %

시편 두께

: 60 ㎛

Thinning method

: jet polishing (No ion-milling)

Strain interval

= 1.0 ㎛/s ~ 0.1 ㎛/s

Strain at fracture

= 290 ㎛

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in in - - situ situ tensile test tensile test

Ti

₄₀

Zr

₂₉

Cu

₉

Ni

₈

Be

₁₄

H.J. Chang et al.

Unpublished. (2008)

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