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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.
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
5. Microstructure = Performance
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
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 e =2.3 VS. ECAP e =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).
16. Mechanical Properties Theoretically we expect the envelope expand to the right
17. Mechanical Properties Theoretically we expect the envelope expand to the right
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