1. 5 Parameter analysis of Modified 316 LN Stainless steel By: Nicholas Bembridge 1 Advisors: Dr Anthony Rollett 2 & Dr Peter Kalu 1 PhD Researchers: Mohammed Alvi 2 Jason Gruber 2 & Steven Downey 1 (1)FAMU FSU College of Engineering (2) Carnegie Mellon University

2. Long term Goal The long term goal of this research is to examine the microstructure and texture changes caused by heat treatment of modified 316LN stainless steel. Current Goals Examine grain boundary character distribution in M316LN stainless steel. Examine grain boundary character distribution in M316LN stainless steel. Determine grain size and twin density with sufficient statistical confidence. Determine grain size and twin density with sufficient statistical confidence.

3. Background 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.

4. Conduit Processing Annealed, Cold rolled – As Received Cold workedCold worked –Jacket Formation (forming & welding) –Magnet coil winding Nb 3 Sn reaction Heat Treatment (100hrs at 700 o C)Nb 3 Sn reaction Heat Treatment (100hrs at 700 o C) Produces superconductor from Cu-Nb wires and TinProduces superconductor from Cu-Nb wires and Tin Primary Selection Criteria for material usePrimary Selection Criteria for material use Cu/Nb 3 Sn Superconductors Heat treatment Cu-NB wires with thin layer of Sn

5. Element 316 LN Wt.% Modified 316LN* Wt% Chromium16.00-18.0017.22 Nickel10.00-14.0013.26 Molybdenum2-32.06 Manganese 2 max 1.51 Silicon.750 max.750 Nitrogen.130-.180.147 Carbon.03 max.005 Niobium No spec..08 Material

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

7. Boundary Plane, n (2 parameters) Lattice Misorientation, ∆g (3 parameters) Grain Boundaries have 5 Macroscopic Degrees of Freedom Grain Boundary Character

8. Experimental Procedure As received M316LN samples were furnace annealed in argon atmosphere at 700 o C for varying lengths of time and water quenched.As received M316LN samples were furnace annealed in argon atmosphere at 700 o C for varying lengths of time and water quenched. *Received in cold rolled and annealed condition. O.I.M. analysis done with Phillips XL-40 FEG SEM Orientation Imaging Microscope and TSL software.O.I.M. analysis done with Phillips XL-40 FEG SEM Orientation Imaging Microscope and TSL software. Between 300x300 and 350x350 micron scan area. Between 300x300 and 350x350 micron scan area. 0.5 micron step size for good resolution. 0.5 micron step size for good resolution.

9. OIM Overview Electron diffraction gives grain orientation.Electron diffraction gives grain orientation. Orientations are measured point by point across the sample’s surface.Orientations are measured point by point across the sample’s surface. 11 22 33

10. Results OIM IPF MapsOIM IPF Maps Twin density dataTwin density data Grain size dataGrain size data Plots of GBCD for as-received, and comparison of as-received with 50 hours annealPlots of GBCD for as-received, and comparison of as-received with 50 hours anneal

11. IPF Maps As Received 100 Hour IPF Map Legend Texture is weak, therefore sample suitable for GBCD analysis

12. Twin density data Typical twin Typical twinned grain

13. Grain size data

14. As Received [100] 30 0 40 0 45 0 60 0 50 0 Misorientations based on [100] show low frequencies; slight bias towards {111} and {110} normals.

15. As Received [110] 30 0 40 0 50 0 60 0 20 0 Peaks present for [110] misorientations at 30°, 40°, with normals between (001) and (1-11); also 60° with (-111).

16. As Received [111] 30 0 40 0 50 0 60 0 20 0 All [111] misorientations favor pure twist boundaries with (111) normals; only 60°[111] shows a massive peak, corresponding to the coherent twin. Peak at (111)-50°[111] may be “leakage” from the coherent twin in (111)-60°[111].

17. Comparative MRD for selected misorientations 50hr 60 0 [110] As Received [110] 60 0 50 0 [111] 50 0 [111]

18. 60 0 [111] As Received50hr [111] 60 0 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

19. Conclusions GBCD is similar to other low stacking fault energy fcc metals such as brass.GBCD is similar to other low stacking fault energy fcc metals such as brass. Negligible changes in Grain size and Twin density.Negligible changes in Grain size and Twin density. Negligible changes in texture.Negligible changes in texture. Negligible changes in grain boundary character distribution as far as 50 hours.Negligible changes in grain boundary character distribution as far as 50 hours. Annealing at 700 0 C has essentially no effect on the microstructure.Annealing at 700 0 C has essentially no effect on the microstructure.

20. 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

21. Any Questions?

22. Supplemental Slides

23. MRD Plots - As Received [100] 5050 10 0 15 0 20 0

24. 10 0 20 0 5050 15 0 MRD Plots - As Received [110]

25. As Received [110] 30 0 40 0 45 0 50 0 60 0

26. MRD Plots - As Received [111] 5050 10 0 15 0 20 0

27. As Received [111] 30 0 40 0 45 0 50 0 60 0