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

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

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?

Possible Applications

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

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

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

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

Thermal Response of Hot Roll Furnace

Actual Thermal History of a Monitored Sample During Grain Initiation

Sample layout Bead on Plate down center of plate Hot work Step Heating Cold Work Samples

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

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

Rolling

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

Polishing Samples surfaces were polished with silicon carbide 240 grit alumina suspension polish to .1 micron

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

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

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

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

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

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

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