5 Parameter analysis of Modified 316 LN Stainless steel

By: Nicholas BembridgBy: Nicholas Bembridgee11

Advisors: Dr Anthony RolleAdvisors: Dr Anthony Rolletttt22

& Dr Peter & Dr Peter KaluKalu11

PhD Researchers: Mohammed AlvPhD Researchers: Mohammed Alvii22

Jason GrubeJason Gruberr22 & Steven Downe & Steven Downeyy11

(1)FAMU FSU College of Engineering (2) Carnegie Mellon University(1)FAMU FSU College of Engineering (2) Carnegie Mellon University

Long term GoalThe long term goal of this research is to examine the microstructure The long term goal of this research is to examine the microstructure and texture changes caused by heat treatment of modified 316LN and texture changes caused by heat treatment of modified 316LN stainless steel.stainless steel.

Current Goals• Examine grain boundary character distribution Examine grain boundary character distribution in M316LN stainless steel.in M316LN stainless steel.

• Determine grain size and twin density with Determine grain size and twin density with sufficient statistical confidence.sufficient statistical confidence.

Background

Currently Modified 316 LN Stainless steel is used as a superconducting wire conduit in Currently Modified 316 LN Stainless steel is used as a superconducting wire conduit in the 45 Tesla Hybrid Magnet System at the National High Magnetic Field Laboratory.the 45 Tesla Hybrid Magnet System at the National High Magnetic Field Laboratory.

Conduit ProcessingAnnealed, Cold rolled – As ReceivedAnnealed, Cold rolled – As Received

• Cold worked Cold worked – Jacket Formation (forming & welding) Jacket Formation (forming & welding)

– Magnet coil windingMagnet coil winding

• NbNb33Sn reaction Heat Treatment (100hrs at 700Sn reaction Heat Treatment (100hrs at 700ooC)C)• Produces superconductor from Cu-Nb wires and Tin Produces superconductor from Cu-Nb wires and Tin

• Primary Selection Criteria for material usePrimary Selection Criteria for material use

Cu/Nb3Sn Superconductors

Heat treatment

Cu-NB wires with thin layer of Sn

ElementElement 316 LN Wt.%316 LN Wt.% Modified 316LN* Wt%Modified 316LN* Wt%

ChromiumChromium 16.00-18.0016.00-18.00 17.2217.22

NickelNickel 10.00-14.0010.00-14.00 13.2613.26

MolybdenumMolybdenum 2-32-3 2.062.06

ManganeseManganese 2 max2 max 1.511.51

SiliconSilicon .750 max.750 max .750.750

NitrogenNitrogen .130-.180.130-.180 .147.147

CarbonCarbon .03 max.03 max .005.005

NiobiumNiobium No spec.No spec. .08.08

Material

Grain Boundary Character

Why do we need 5 parameters?Why do we need 5 parameters?- Describing a grain boundary requires a - Describing a grain boundary requires a misorientation (3 parameters) misorientation (3 parameters) andand a normal (2 a normal (2 parameters).parameters).Why might the 5 parameter distributions be Why might the 5 parameter distributions be interesting?interesting?- This material has a high density of twins, so we - This material has a high density of twins, so we would like to know if the twins are all coherent would like to know if the twins are all coherent twins; also we would like to know if any other twins; also we would like to know if any other boundary types are favoredboundary types are favored

““GBCD” = Grain Boundary Character DistributionGBCD” = Grain Boundary Character Distribution

Experimental Procedure• As received M316LN samples were furnace As received M316LN samples were furnace

annealed in argon atmosphere at 700annealed in argon atmosphere at 700oo C for C for varying lengths of time and water quenched.varying lengths of time and water quenched.

*Received in cold rolled and annealed condition.*Received in cold rolled and annealed condition.

• O.I.M. analysis done with Phillips XL-40 O.I.M. analysis done with Phillips XL-40 FEG SEM Orientation Imaging Microscope FEG SEM Orientation Imaging Microscope and TSL software. and TSL software.

• Between 300x300 and 350x350 micron Between 300x300 and 350x350 micron scan area.scan area.

• 0.5 micron step size for good resolution.0.5 micron step size for good resolution.

OIM Overview• Electron diffraction gives grain orientation. Electron diffraction gives grain orientation. • Orientations are measured point by point Orientations are measured point by point

across the sample’s surface.across the sample’s surface.

1 1

2 233

Results

• OIM IPF MapsOIM IPF Maps

• Twin density dataTwin density data

• Grain size dataGrain size data

• Plots of GBCD for as-received, and Plots of GBCD for as-received, and comparison of as-received with 50 hours comparison of as-received with 50 hours annealanneal

IPF Maps

As ReceivedAs Received 100 Hour100 Hour

IPF Map LegendIPF Map Legend

Texture is weak, therefore sample suitable for GBCD analysisTexture is weak, therefore sample suitable for GBCD analysis

Twin density dataTwin Fraction VS Annealing Time

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

-10 10 30 50 70 90 110

Annealing Tim e (hours)

Tw

in F

ract

ion

Typical twin

Typical twinned grain

Grain size dataGrain Diameter With Twins VS Annealing Time

0

1

2

3

4

5

6

7

-10 10 30 50 70 90 110

Annealing Tim e (hours)

Gra

in D

iam

eter

(m

icro

ns)

• As Received [100]

300 400

450

600

500

Misorientations based on [100] Misorientations based on [100] show low frequencies; slight bias show low frequencies; slight bias towards {111} and {110} normals.towards {111} and {110} normals.

• As Received [110]

300

400 500

600

200

Peaks present for [110] Peaks present for [110] misorientations at 30°, 40°, with misorientations at 30°, 40°, with normals between (001) and (1-11); normals between (001) and (1-11); also 60° with (-111).also 60° with (-111).

• As Received [111]

300

400 500

600

200

All [111] misorientations favor pure twist All [111] misorientations favor pure twist boundaries with (111) normals; only boundaries with (111) normals; only 60°[111] shows a massive peak, 60°[111] shows a massive peak, corresponding to the corresponding to the coherent twincoherent twin. Peak . Peak at (111)-50°[111] may be “leakage” from at (111)-50°[111] may be “leakage” from the coherent twin in (111)-60°[111].the coherent twin in (111)-60°[111].

Comparative MRD for selected Comparative MRD for selected misorientationsmisorientations

50hr

600

[110]

As Received

[110]

600

500

[111]

500

[111]

600

[111]

As Received 50hr

[111]

600

Comparison Continued

• Peaks occur at similar locationsPeaks occur at similar locations

• Peaks have similar intensitiesPeaks have similar intensities

• No change in GBCDNo change in GBCD

Conclusions

• GBCD is similar to other low stacking fault GBCD is similar to other low stacking fault energy fcc metals such as brass.energy fcc metals such as brass.

• Negligible changes in Grain size and Twin Negligible changes in Grain size and Twin density.density.

• Negligible changes in texture.Negligible changes in texture.• Negligible changes in grain boundary Negligible changes in grain boundary

character distribution as far as 50 hours.character distribution as far as 50 hours.• Annealing at 700Annealing at 7000 0 C has essentially no effect C has essentially no effect

on the microstructureon the microstructure..

Acknowledgements

• Dr. Kalu 1

• Dr. Rollett 2

• Steven Downey 1

• Mohammed Alvi 2

• Jason Gruber 2

• Herb Miller 2

• Tricia Bennett 2

(1)FAMU/FSU College of Engineering (2) Carnegie Mellon University

Any Questions?Any Questions?

Supplemental Slides

MRD Plots - As Received [100]

50 100

150 200

100

200

50

150

MRD Plots - As Received [110]

• As Received [110]

300 400

450 500

600

MRD Plots - As Received [111]

50 100

150 200

• As Received [111]

300 400

450 500

600