What is Abnormal Grain Growth?

1. The Effect of Thermal-mechanical Treatment on Abnormal Grain Growth on Friction Stir Welded Al-Li 2195Richard Wellnitz & Anthony D. BarajasDr Howard – project superviser

2. Abnormal Grain Growth Normal Grain Growth What is Abnormal Grain Growth? SAMPLE H STD Massive Grains (.5-1 mm) Small Rounded Grains (3-5 microns)

3. Objective To Find Out • Does Hot rolling have an affect on grain growth? • Does cold rolling have an affect on grain growth? • Does step heating have an affect on grain growth?

4. Possible Applications

5. Other possible applications • Other possible applications in pictures examples of cars trains planes etc.

6. Presentation Organization • Introduction • Theory • Methods and Equipment • Charts • Description of Results • Summary and Conclusions

7. Theory Introducing a process of cold working or cold rolling may inhibit this formation of abnormal grain growth by breaking the structures along the slip plane. Face Centered Cubic on 1 1 1 plane Shifting along the Slip plane

8. The FSW equipment FSW AT 200 RPM 4 IPM TOOL ANGLE 3.5 DEG POSITION CONTROL WITH 0.010 “HEEL PLUNGE

10. Thermal Response of Hot Roll Furnace

11. Actual Thermal History of a Monitored Sample During Grain Initiation

13. Sample layout Bead on Plate down center of plate Hot work Step Heating ColdWork Samples

14. Step Heating • Step heating-Initially brought up to 750 F And continually increased by 50 degrees each hour afterwards to 950 F 50 F 950 F 1 HOUR 50 F Temp 1 HOUR 50 F 1 HOUR 50 F 1 HOUR 750 F Oven and samples heated to 750 degrees prior to step heating Time

15. Standard Samples STD STD-FSW Only H-Heated with hot roll samples ASAW – FSW and Solution Heat treatment ASFSW- FSW Only

16. Rolling

17. Processing schedules • Hot work- 10%,20%,30%,40% • Cold work- 5%,20%,25%,30% % OF REDUCTION THICKNESS OF SAMPLE T 1 T 2

18. Polishing Samples surfaces were polished with silicon carbide 240 grit 400 grit 600 grit 800 grit 1200 grit alumina suspension polish to .1 micron

19. Etching Etching- bringing out the grain Samples were etched with 10% Sodium Hydroxide solution – 60 seconds Rinsed –distilled water Washed in– 50% Nitric Acid Solution Rinsed –distilled water

20. Results of Hot Roll Reduction 10% 20% 30% 40% .320 Original Thickness

21. Results of Cold Roll Reduction 5% 20% 25% 30% .320 Original Thickness

22. Conclusions • Substantial Grain growth occurs in Al-Li 2195 • Hot working doesn’t eliminate or reduce grain growth • Hot work might actually increase grain growth • There is substantial grain growth reduction above 20% cold rolling • Step heating does not decrease grain growth

23. Suggested additional work • Image analysis for grain size (statistical) • Additional cold work between 5% and 20% • Further metallurgical testing for hardness toughness • Tensile strength ductility • Fatigue life • Microscopy

24. Bill Arbegast-AMP Dr. Stone-MET Santosh Koduri K.B. Anand Srikanth Labhala Eric Henderson Tyler Engstrom Colleen Gustafson Casey Allen Brian Tweedy Acknowledgements

25. Discussion • Why is cold work effective • At what point is cold work effective • Does hot rolling increase the grain growth