# Presentation: 491560

## Equal-Channel Angular Pressing (ECAP) and High-Pressure Torsion (HPT)

ECAP and HPT are used to fabricate ultrafine-grained microstructures with grain sizes <1000 nm.
Hardness measurements demonstrate the development of homogeneity after processing: illustrations (right) show an inhomogeneous microstructure after 1 turn of HPT (upper) and a more homogeneous microhardness after 5 turns (lower).
Materials processed by ECAP and HPT are under evaluation for use in superplastic forming operations.

- ECAP and HPT are used to fabricate ultrafine-grained microstructures with grain sizes <1000 nm.
- Hardness measurements demonstrate the development of homogeneity after processing: illustrations (right) show an inhomogeneous microstructure after 1 turn of HPT (upper) and a more homogeneous microhardness after 5 turns (lower).
- Materials processed by ECAP and HPT are under evaluation for use in superplastic forming operations.

**Creep and Superplasticity ****in Materials with Ultrafine Grain Sizes****Terence G. Langdon, University of Southern California, DMR 0243331**

- M. Kawasaki, C. Xu and T.G. Langdon, “An Investigation of Cavity Growth in a Superplastic Aluminum Alloy Processed by ECAP,” Acta Materialia _53_, 5353 (2005).
- C.Xu, Z. Horita and T.G. Langdon, “The Evolution of Homogeneity in Processing by High-Pressure Torsion,” Acta Materialia _55_, 203 (2007).
- M. Kawasaki and T.G. Langdon, “Properties of Superplasticity in Ultrafine-Grained Materials,” Journal of Materials Science _42_, 1782 (2007).

- _Al-6061: P = 4 GPa, 5 turns_

- _Al-6061: P = 4 GPa, 1 turn _

**Notes:**
Processing by ECAP and HPT provide the opportunity of producing remarkable grain refinement in bulk solids and in producing fully-dense materials with grain sizes in the submicrometer or nanometer range.  As a result of the very small grain sizes, these materials exhibit high strength and, provided the grain structure is reasonably stable, excellent forming capabilities at elevated temperatures.
An important consideration in the production of these materials concerns the degree of homogeneity that may be attained after processing.  The two images on the right show three-dimensional plots of the hardness across disks of pure aluminum that were processed by HPT under an imposed pressure of 4.0 GPa.  The upper image was taken after a single turn of torsional strain and in this material the structure is inhomogeneous with lower values of the hardness in the center.  The lower image shows a similar specimen after 5 turns where there is now an evolution into a more homogeneous structure but with a small area of low hardness near the center.  

## Creep and Superplasticityin Materials with Ultrafine Grain SizesTerence G. Langdon, University of Southern California, DMR  0243331

**Training**
- 2 graduate students (Megumi Kawasaki and Roberto Figueiredo) and 1 post-doc (Dr. Cheng Xu) are participating in this research.
- Collaborations are in place with Kyushu University, Japan, and the University of Southampton, U.K.

**Impact**
- Invited lectures describing the results were presented at international conferences in Canada, Germany, Japan, Poland, Russia, Spain, U.K., U.S.A.
- The P.I. co-organized conferences on Ultrafine-Grained Materials in Spain (2003); Charlotte, N.C. (2004); Japan (2005); San Antonio, TX (2006); Ufa, Russia (2007).
- The post-doc (Dr. Cheng Xu) and student (Megumi Kawasaki) won awards for best oral presentations at the TMS Annual Meetings in Charlotte, N.C. (2004) and San Antonio, TX (2006).

- (From left) Megumi Kawasaki, Prof. Langdon, Dr. Cheng Xu and Roberto Figueiredo at the BNM-2007 International Symposium on Bulk Nanostructured Materials in Ufa, Russia, in August 2007

**Notes:**
This program provided support for a female post-doc (Dr. Cheng Xu) and a female graduate student (Ms. Megumi Kawasaki).  In addition, an Hispanic graduate student (Roberto Figueiredo) was supported by a Fulbright Scholarship.  All of these research personnel are excellent.  
Dr. Xu has already published more than 40 papers in refereed journals.  She was an invited speaker at the 5th Pacific Rim Conference in China and at the ASM Advanced Aerospace Materials and Processes Conference in Seattle.  She was awarded first prize for her oral presentations at the TMS Annual Meetings in Charlotte, N.C., in 2004 and San Antonio, TX, in 2006.  She has been awarded a WiSE (Women in Science and Engineering) Senior Research Fellowship for 2006-2008.
Graduate student Megumi Kawasaki has already published seven papers in scientific journals.  She was awarded second place for her poster at the TMS Annual Meeting in Charlotte (2004) and second place for her oral presentation at the TMS Annual Meeting in San Antonio (2006).
Graduate student Roberto Figueiredo has published two papers in scientific journals during the first two years of his Ph.D. research at USC.
Prof. Langdon has been active in organizing international meetings on ultrafine-grained materials.  He was the Co-Chairman (with Prof. Ruslan Valiev) of BNM-2007, the “International Symposium on Bulk Nanostructured Materials: from Fundamentals to Innovation” which was held in Ufa, Russia, on August 14-18, 2007.
Prof. Langdon is scheduled to receive the Albert Sauveur Achievement Award from ASM International in September 2007.