# Presentation: 491557

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

ECAP and HPT are used to process ultrafine-grained microstructures.
Grain sizes are generally in the range 100-1000 nm.
Hardness measurements demonstrate the development of homogeneity after processing: illustrations (right) show an inhomogeneous microstructure after 1 turn of HPT (upper) and a homogeneous microhardness distribution after 5 turns (lower).
Materials processed by ECAP and HPT are excellent candidate materials for use in superplastic forming operations.

- ECAP and HPT are used to process ultrafine-grained microstructures.
- Grain sizes are generally in the range 100-1000 nm.
- Hardness measurements demonstrate the development of homogeneity after processing: illustrations (right) show an inhomogeneous microstructure after 1 turn of HPT (upper) and a homogeneous microhardness distribution after 5 turns (lower).
- Materials processed by ECAP and HPT are excellent candidate materials for use in superplastic forming operations.

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

- C. Xu, M. Furukawa, Z. Horita and T.G. Langdon, “Influence of ECAP on Precipitate Distributions in a Spray-Cast Aluminum Alloy,” Acta Materialia _53_, 749-758 (2005).
- 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 (2006) in press.

**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 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 the variation in hardness across disks of pure aluminum that were processed by HPT under an imposed pressure of 1.25 GPa.  The upper image was taken after a single turn of torsional strain and in this material the structure is inhomogeneous (as shown by the higher values of hardness recorded near the center of the disk).  The lower image shows a similar specimen after 5 turns where there is now an acceptable level of homogeneity across the disk.  

## Training
3 graduate students and 1 post-doc are participating in this research.
Collaborations are in place with Kyushu University, Japan, and the University of Southampton, U.K.

- 3 graduate students and 1 post-doc are participating in this research.
- Collaborations are in place with Kyushu University, Japan, and the University of Southampton, U.K.

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

- Impact
- Invited lectures describing the results were presented at international conferences in the Czech Republic, Japan, Poland, Russia, Spain, Ukraine, U.K., U.S.A.
- The P.I. is co-organizer of conferences on Ultrafine-Grained Materials in Spain (2003); Charlotte, N.C. (2004); Japan (2005); San Antonio, TX (2006); Ufa, Russia (2007).
- The post-doc and student won awards for best oral presentations at the TMS Annual Meetings in Charlotte, N.C. (2004) and San Antonio, TX (2006).

- Dr. Cheng Xu and Prof. Langdon prepare ultrafine-grained materials using Equal-Channel Angular Pressing at the University of Southern California

- Graduate student Megumi Kawasaki with the High-Pressure Torsion facility

**Notes:**
This program provides support for a female post-doc (Dr. Cheng Xu) and a female graduate student (Ms. Megumi Kawasaki).  In addition, another student (P. Kumar) is supported by a Teaching Assistantship and an Hispanic student (Roberto Figueiredo) is supported by a Fulbright Scholarship.
All of these research personnel are excellent.  Dr. Xu has already published more than 15 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.
Graduate student Megumi Kawasaki has already published four 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).
Prof. Langdon has been active in organizing international meetings on ultrafine-grained materials.  Currently, he is the Co-Chairman (with Prof. Ruslan Valiev) of the “International Symposium on Bulk Nanostructured Materials: from Fundamentals to Innovation” to be held in Ufa, Russia, on August 14-18, 2007.