x-ray microdiffraction on diamond-shaped niti for biomedical applications

$: X-Ray Microdiffraction on Diamond-shaped NiTi for Biomedical Applications$
8th Jun. 2003 SEM X International Congress

X-Ray Microdiffraction on Diamond-shaped NiTi for Biomedical Applications

Apurva Mehta

SSRL/ SLAC, Stanford University

Valentina Imbeni


Apurva MehtaNew Boss


Apurva MehtaCollaborators

Valentina Imbeni – SRI

Brad Boyce – Sandia Labs

Nobumichi Tamura – LBL

Xiao-Yan Gong, Alan Pelton, & Tom Duerig –

NDC

Rob Ritchie’s Group (Scott Robertson, Monica

Barney) – LBL/ UC Berkeley


Apurva Mehta

Motivation:Macroscopic --- Microscopic

Understanding of Deformation and Failure of NiTi components at Local Level under Multiaxial Loading.

Validation of Design Models. Towards Improved Models that

include: Austenite to Martensitic Phase Transition Mechanics Beyond Continuum Mechanics.

In vivo loadingIn vivo loadingfracturesfractures


Apurva Mehta

MotivationE.g., understanding Fatigue Tests

Location of Fracture

Increase of Fatigue Life Above 1.5% Strain !!

0.0

0.2

0.4

0.6

0.8

1.0

-4 -3 -2 -1 0 1 2 3 4

Mean Strain (%)

Hal

f Alt

ern

atin

g S

trai

n (

%)

BrokenRun Out

A. Pelton et. al. - NDC


Apurva MehtaTalk Outline

What did we do? Methodology

What did we find? Diamond in Compression Diamond in Compression Cycling Diamond in Tension

Five “New” Insights


Apurva Mehta

MethodologyLoad Cell

FEA Simulations

X-ray Beam

Tension

•Nitinol Tube 4.67mm OD with 0.38mm wall

•Laser machined

•Fully Annealed – Grains ~ 20-100 microns

compression


Apurva Mehta

Bend MagnetSource(250x40m)

1:1 Toroidalmirror

1:1 imageat slits

Elevation view

Plan view

4 CrystalSi(111)Monochromator

CCDcamera

Sampleon scanningXY stage

Horizontal focusing K-B mirror Vertical focusing K-B mirror

MethodologyX-ray Microdiffraction

Beam size on sample: 0.8x0.8 m2

Photon energy range: 5-14 keV

Schematic layout of the X-ray Microdiffraction

Beamline (7.3.3.) at the ALS


Apurva Mehta

MethodologyX-ray Microdiffraction-1 micron spot

NiTi Diffraction Patterns

10 m Grain Map

Elastic Strain

Plastic Strain

• Ni & Ti Fluorescence

• Austenite Diff. Pattern


Apurva Mehta

300

03

0

003

3'

3'

3'

332313

232212

131211

332313

232212

131211

ij

DeviatioricDeviatioric DilationalDilational

kkkb o )(lkkc o )(hkka o )(

From energy scan(Variably Monochromated X-rays)

From Laue Patterns deviations(broad bandpass (White) X-rays)

Strain Tensor

Strain TensorsIn crystal reference

frame

xx xy xz

xy yy yz

xz yz zz

+

Crystal OrientationFrom Laue Patterns

In Sample reference frame


Apurva MehtaDisplacement Strain


Findings


Apurva Mehta

CompressionD = 0 mm : F = 0 N

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

-1.5%

1.5% 0.0 mm

xx

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

X (microns)

Y (

mic

rons

)

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

-1.5%

1.5%0.0 mm

yy

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

X (microns)Y

(m

icro

ns)

xx yy


Apurva Mehta

CompressionD = 0.5 mm : F = -0.393 N

0 50 100 150 200 250 300 350 400500

400

300

200

100

01.5%

-1.5%

Y (

mic

rons

)X (microns)

Compression 0.5 mm

yy

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

Y (

mic

ron

s)

X (microns)

1.5%

-1.5%

Compression 0.5 mm

xx

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

xx yy

-4 -3 -2 -1 0

-1.5

-1.0

-0.5

0.0

0.5

For

ce (

N)

Displacement (mm)


Apurva Mehta


0 50 100 150 200 250 300 350 400500

400

300

200

100

0

Y (

mic

rons

)

X (microns)

-1.5%

1.5%Compression 1.0 mm

xx

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

xx yy

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

-1.5%

1.5%

Y (

mic

rons

)X (microns)

Compression 1.0 mm

yy

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

-4 -3 -2 -1 0

-1.5

-1.0

-0.5

0.0

0.5

For

ce (

N)

Displacement (mm)


Apurva Mehta


0 50 100 150 200 250 300 350 400500

400

300

200

100

01.5%

-1.5%

X (microns)Y

(m

icro

ns)

Compression 1.5 mm

yy

-15.00

-14.00

-13.00

-12.00

-11.00

-10.00

-9.000

-8.000

-7.000

-6.000

-5.000

-4.000

-3.000

-2.000

-1.000

0

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

9.000

10.00

11.00

12.00

13.00

14.00

15.00

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

-1.5%

1.5%

Y (

mic

rons

)

X (microns)

Compression 1.5 mm

xx

-15.00

-14.00

-13.00

-12.00

-11.00

-10.00

-9.000

-8.000

-7.000

-6.000

-5.000

-4.000

-3.000

-2.000

-1.000

0

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

9.000

10.00

11.00

12.00

13.00

14.00

15.00

xx yy

-4 -3 -2 -1 0

-1.5

-1.0

-0.5

0.0

0.5

For

ce (

N)

Displacement (mm)


Apurva Mehta


0 50 100 150 200 250 300 350 400500

400

300

200

100

0 1.5%

-1.5%

Y (

mic

rons

)X (microns)

Compression 2.5 mm

yy

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

0 50 100 150 200 250 300 350 400500

400

300

200

100

0 1.5%

-1.5%

Y (

mic

rons

)

X (microns)

Compression 2.5 mm

xx

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

xx yy

-4 -3 -2 -1 0

-1.5

-1.0

-0.5

0.0

0.5

For

ce (

N)

Displacement (mm)


Apurva Mehta


0 50 100 150 200 250 300 350 400500

400

300

200

100

0

-1.5%

1.5%

Y (

mic

rons

)X (microns)

Compression 3.7 mm

yy

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

-1.5%

1.5%

Y (

mic

rons

)

X (microns)

Compression 3.7 mm

xx

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

xx yy

-4 -3 -2 -1 0

-1.5

-1.0

-0.5

0.0

0.5

For

ce (

N)

Displacement (mm)


Apurva Mehta


0 50 100 150 200 250 300 350 400500

400

300

200

100

0

-1.5%

1.5%

Y (

mic

rons

)

X (microns)

Compression 3.7 mm

yy

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

-4 -3 -2 -1 0

-1.5

-1.0

-0.5

0.0

0.5

For

ce (

N)

Displacement (mm)

Phase Map

yy

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

Y (

mic

ron

s)

X (microns)

Compression 3.7 mm

Austenite

Martensite


Apurva MehtaInsight #1

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

-1.5%

1.5%

Y (

mic

ron

s)

X (microns)

Compression 3.7 mm

yy

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

Finite Elem. Analysis Microdiffraction

3.7 mm compression

Qualitative agreement with FEA

But – Granular and Speckled

X. –Y. Gong et al.



Local Strain Never exceeds 1.5 %

NiTi Superelastic because the Aust. And Mart. Elastic region separated by a large region of Transformation Strain

Mar

tens

ite

Aust

enit

e

Molar vol ~ strain 1.5%

Aust + Mart2 phase region

Transformation strain @

const. Stress



Strain relief on transformation

Strain reversal

140 145 150 155 160

150

140

130

120

110

100

yy

X (microns)

Y (

mic

rons

)

Aust

enit

eMolar vol ~ strain

1.5%

Nucleation energy


Apurva Mehta

CompressionD = 2.5 mm unload : F = -1.037 N

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

-1.5%

1.5%

X (microns)

Y (

mic

rons

)

xx

Compression 2.5 mm on unload

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

-1.5%

1.5%

Y (

mic

rons

)X (microns)


yy

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

xx yy

-4 -3 -2 -1 0

-1.5

-1.0

-0.5

0.0

0.5

For

ce (

N)

Displacement (mm)


Apurva Mehta

CompressionD = 0.0 mm unload : F = +0.282 N

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

-1.5%

1.5%

Y (

mic

rons

)X (microns)


yy

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

Y (

mic

rons

)

X (microns)

-1.5%

1.5%Compression 0.0 mm on unload

xx

-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

xx yy

-4 -3 -2 -1 0

-1.5

-1.0

-0.5

0.0

0.5

For

ce (

N)

Displacement (mm)


Apurva MehtaLoad Cycling @3.7 mm

0 50 100 150 200 250 300 350 400500

400

300

200

100

0

Y (

mic

rons

)

X (microns)

Compression 3.7 mm

0 50 100 150

100

0

Martensite map

X (microns)

Y (

mic

rons

)

0 50 100 150

160

140

120

100

80

60

40

20

0

yy

X (microns)

Y (

mic

rons

)

0 20 40 60 80 100 120 140 160 180

160

140

120

100

80

60

40

20

0

Martensite map

X (microns)

Y (

mic

rons

)

0 20 40 60 80 100 120 140 160 180

140

120

100

80

60

40

20

0

yy

X (microns)

Y (

mic

rons

)

0 20 40 60 80 100 120 140 160 180

140

120

100

80

60

40

20

0

Martensite map

X (microns)

Y (

mic

ron

s)

0 20 40 60 80 100 120 140 160 180

140

120

100

80

60

40

20

0 yy

X (microns)

Y (

mic

rons

)

-5 -4 -3 -2 -1 0

-1.5

-1.0

-0.5

0.0

0.5

Force

(N)

Displacement (mm) Zero Cycles0 – 3.7 mm

One Cycles3.7- 0- 3.7 mm

Eleven Cycles4.9 – 2.5 - 3.7 mm



On cycling Martensitic region grows.

Growth Pattern unpredictable from FEA

Strain relief as Martensite grows

Explanation for increased Fatigue Life for macroscopic strains > 1.5 %


Apurva Mehta

Tension : yy

-200 -100 0 100 200 300-150

-100

-50

0

50

100

150

200

250

300

350

400

Tension 3.0 mm

yy

-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

X (microns)

Y (

mic

rons

)

-200 -150 -100 -50 0 50 100 150 200 250 300

-100

0

100

200

300

400

Tension 2.0 mm

yy

-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

X (microns)Y

(m

icro

ns)

-200 -100 0 100 200 300

-100

0

100

200

300

400

Tension 0.3 mm

yy

-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

X (microns)

Y (

mic

ron

s)

-200 -100 0 100 200 300

-100

0

100

200

300

400

Tension 6.0 mm

yy

-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

X (microns)

Y (

mic

rons

)

-200 -100 0 100 200 300

-100

0

100

200

300

400

Tension 5.0 mm

yy

-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00

X (microns)

Y (

mic

rons

)



Transformation front and hence stress “hotspot” changes direction, and traverses down the stem of the diamond.

Failure occurs when the “hotspot” encounters a defect or weakness in the material. Location of failure maybe different from FEA prediction.


Apurva MehtaSummary

Insights: Strain map granular, martensite evolution speckled. In the superelstic region max stress doesn’t exceed

stress corresponding to 1.5% Austenite strain. Strain relief and strain reversal at the transformation

front. On load cycling, the martensite region grows. Overall

stress drops. Transformation and max stress front changes directions.

Further Questions: What is the crystallographic relationship between the

Martenite and the Austenite phase? What happens around a crack tip?


Apurva Mehta

Crystallographic Relationships


Thanks !

x-ray microdiffraction on diamond-shaped niti for biomedical applications

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