Equal Channel Angular Pressing of High Purity Aluminum

1. Equal Channel Angular Pressing of High Purity Aluminum Julio A. Nunez Chris Hovanec Dr. Surya R. Kalidindi Dr. Roger D. Doherty Mechanics of Microstructures Group

2. Equal Channel Angular Pressing(ECAP) Deformation process that imposes high strains with the benefit of retaining the cross-sectional area of the work piece. Shear Plane

3. Motivation • The likelihood that ultra fine grain aluminum and its alloys can be produced by ECAP processing with both increased strength and fracture toughness. • To achieve a more in-depth understanding of the physical mechanisms behind the evolution of grain size and shape during severe plastic deformation.

4. Social/Economical F-22 Space Shuttle 10% Reduction/6% efficiency Thrust High =Higher Acceleration Weight Dodge Viper

5. Microstructure = Performance Performance Processing Microstructure

6. Two Ways to Strengthen Metals • Precipitation Hardening • Strain Hardening

7. Precipitation Hardening • Precipitation Hardening is a thermodynamic reaction that involves creation of a new phase change • Precipitation Heat Treatment: • precipitates form on grain boundaries • lower fracture toughness compared to strain hardening Grain Boundaries

8. Strain Hardening • Strain Hardening occurs when a ductile metal becomes harder and stronger as it is plastically deformed • rolling, compression, and ECAP

9. Rolling • Widely used for strain hardening • Pass a piece of metal between two rolls • Although imposes strain on the metal, it reduces thickness • Sample thickness limits amount of strain induced

10. Aluminum • Generally precipitation heat treated because of inherent properties • Lowers fracture toughness • Dr. Doherty and colleagues discovered high solute alloys increase fracture toughness when strained

11. ECAP • Same strength as precipitation hardening but higher fracture toughness • Rolling ε =2.3 VS. ECAP ε =10

12. Objectives • Successfully process high purity Al by ECAP to high strains • Extract mechanical properties as a function of imposed strain • Extract mechanical properties as a function of microstructure • Validate the MMG ECAP process through comparisons of experimental data & published data

13. Procedure • Run each sample twice and heat treat at 450C for 1hr • Run ten samples to different strains through route “A” • Cut samples • Run compression test • Perform metallography to measure grain size and analyze texture

14. Microstructure • Metallography is the process of preparing samples such that any deform or unrepresented surface is removed so the specimen is ready for analysis. • Grain Size • Texture OIM (measure of crystal orientations). SEM OIM

15. Grinding wheel Grinding/Polishing • Grinding is done on a spinning wheel with water running on the surface. • Round SiC grinding paper are used to scratch the surface with all the lines going in one direction. • Polishing creates a smooth, mirror-like finish. • Non-abrasive cloth is used and lubricant is added and a diamond suspension which acts as grit. Different grit papers Cloth, lubricant, and diamond suspension

16. Mechanical Properties • Theoretically we expect the envelope expand to the right Fracture Toughness KIC Yield Strength σy

17. Mechanical Properties • Theoretically we expect the envelope expand to the right Fracture Toughness KIC Yield Strength σy

18. Results • Results from testing will be used to compare data from previous published findings. • If the data correlates, this will validate proper technique and give us a base line for our overall project.

19. Thank You

20. Dislocations Linear or one dimensional defects where some of the atoms are misaligned.