characterization of void growth in high temperature fatigued copper through usans guangjun cheng...

Characterization of Void Growth in High Temperature Fatigued

Copper through USANS

Guangjun Cheng Stephen Fenimore

Rohan Hule Jinkee Lee

Christopher MettingMaria Torija

Outline

• USANS

• Problem background

• Experimental design

• Analysis

• Results

• Conclusions

USANS Capabilities

Graphite Filter

Sapphire Filter

Premonochromator

Monochromator

Monitor

Sample Changer

Main Detector

Analyzer

Transmission

Detector Isolation Table

Apertures

Scale: 1 m PCD Simplified Layout3.CV5

• Low q range– 3x10-5 Å-1 < q < 0.01 Å-1

• Particle Diameter: 0.1 μ m < D < 10 μm

Problem Background

• Fatigue causes voids in copper lattice

• Voids grow nucleate at grain boundaries

• Lead to mechanical failure

• Relationship between stress and void growth

Stress Axis

fatigue_cavity.CV5

Void

Grain Boundary (Diamond Configuration)

Experimental Design

• Fatigue conditions– 405 oC– 17 cycles/second– Max stress amplitude: 34 MPa

• Monitor void growth by varying the number of fatigue cycles– 25,000; 50,000; 100,000 cycles

• USANS to examine growth shape and size

Reduced Slit Smeared USANS DataSlope= -1 (plate)

Slope= -3 (Porod)

Porod Scattering, 100,000 cycles

0 100

1 10 -7

2 10 -7

3 10 -7

4 10 -7

5 10 -7

6 10 -7

7 10 -7

8 10 -7

0 100 5 10 -4 1 10 -3 1.5 10 -3 2 10 -3 2.5 10 -3

q•d

s/d

(q

)

Å-1

cm

-1

q (Å-1 )

blue_Porod.gra

3

Intercept ~surface area/sample volume-3

Invariant

0

0.5

1

1.5

2

2.5

3

3.5

4

0 100 5 10-4 1 10-3 1.5 10-3 2 10-3 2.5 10-3

q•d

/d

(q

)

Å-1

cm

-1

q (Å-1 )

blue_invariant.gra

Area under curve ~ Volume Fraction

Modified Guinier (plate)

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

0 100 5 10 -7 1 10 -6 1.5 10 -6 2 10 -6 2.5 10 -6 3 10 -6 3.5 10 -6 4 10 -6

ln(q

•d

s/d

(q

))

Å-1

cm

-1

q2 (Å-2 )

blue_mGuinier.gra

m= -T2/12

Results

Number of Cycles

  25,000 50,000 100,000

Surface area/Sample volume (cm2/cm3) 160 240

Volume fraction 5.80E-04 1.70E-03 2.90E-03

Average diameter (m) 0.60 0.72

Average volume (m3) 0.11 0.20

Number of voids/sample volume (cm-3) 1.50E+10 1.40E+10

Plate thickness (m) 0.36 0.55 0.63

Comparison with prior workScripta Met. 24 (1990) 227-232

Conclusions

• USANS proved to be a powerful tool for this investigation

• Average volume increases with cycle number

• Number of nucleation sites is independent of the number of cycles

HURRAY for USANS!

Thanks to John Barker, Man-Ho Kim, and David Mildner

Questions?

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Data reduction for USANS:Smearing corection

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Particle Volume fraction- Invariant

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