Abstract
Mechanical properties of most metallic materials can be improved by reducing their grain size. One of the methods used to reduce the grain size even to the nanometer level is the severe plastic deformation processing. Equal Channel Angular Pressing (ECAP) is one of the most promising severe plastic deformation processes for nanocrystallization of ductile metals. Nanocrystalline and ultrafine grained metals usually have significantly higher strength properties but lower tensile ductility compared to the coarse grained metals. In this work, the torsion properties of ECAP processed ultrafine grained pure 1070 aluminum were studied in a wide range of strain rates using both servohydraulic materials testing machines and Hopkinson Split Bar techniques. The material exhibits extremely high ductility in torsion and the specimens did not fail even after 300% of strain. Pronounced yield point behavior was observed at strain rates 500 s-1 and higher, whereas at lower strain rates the yielding was continuous. The material showed slight strain softening at the strain rate of 10-4 s-1, almost ideally plastic behavior at strain rates between 10-3 s-1 and 500 s-1, and slight but increasing strain hardening at strain rates higher than that. The tests were monitored using digital cameras, and the strain distributions on the surface of the specimens were calculated using digital image correlation. The strain in the specimen localized very rapidly after yielding at all strain rates, and the localization lead to the development of a shear band. At high strain rates the shear band developed faster than at low strain rates.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
ReferenceS
May J. Höppel H., Göken M., Strain rate sensitivity of ultrafine-grained aluminum processed by severe plastic deformation. Scripta Materialia, 53, pp. 189-194, 2005.
El-Danaf E. Mechanical properties and microstructure evolution of 1050 aluminum severely processed by ECAP to 16 passes. Materials Science and Engineering A, 487, pp 189-200, 2008.
El-Danaf E., Soliman M. Almajid A., El-Rayes M., Enhancement of mechanical properties and grain size refinement of commercial purity aluminum 1050 processed by ECAP. Materials Science and Engineering A, 458, pp 226-234, 2007.
Kokkonen J. Kuokkala V.-T., Lech Olejnik, Andrzej Rosochowski, Dynamic behavior of ECAP processed aluminum at room and sub-zero temperatures. In the proceedings of the annual SEM conference, Orlando Fl, 2008.
Rosochowski A., Olejnik L. Numerical and Physical modeling of plastic deformation in 2-turn equal angular extrusion. Journal of Materials Processing Technology, 125-126, pp. 309-316, 2002.
Olejnik L. Rosochowski A., Methods of fabrication metals from nano-technology. Bulletin of the Polish Academy of Sciences, Technical Sciences, 53, pp. 413-423, 2005.
Gilat A., Torsional Kolsky bar testing. ASM Handbook, 8, Materials Park, Ohio, USA, 2000.
Kokkonen J., Kuokkala V.-T., Seidt J., Walker A., Gilat A., Olejnik L., Rosochowski A. High strain rate deformation analysis of UFG aluminum sheet samples. In the proceedings of the annual SEM conference, Albuquerque NM, 2009.
Kuokkala V.-T., Kokkonen J., Song B., Chen W., Olejnik L., Rosochowski A., Dynamic responce of severe plastic deformation processed 1070 aluminum at various temperatures. In the proceedings of the Dymat Technical Meeting, Bourges, France, 2008.
Valiev R., Langdon T. Principles of equal-channel angular pressing as a processing tool for grain refinement. Progress in Materials Science, 51, pp 881-981, 2006.
Kokkonen J., Kuokkala V.-T., Isakov M., Dynamic behavior of UFG aluminum at a wide range of strain rates and temperatures in compression and tension. Journal de Physique IV, 1, pp. 647-653, 2009.
Sivaraman A., Chakkingal U., Investigations on workability of commercial purity aluminum processed by equal channel angular pressing. Journal of Materials Processing Technology, 202, pp. 543-548, 2008.
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2011 Springer Science+Business Media, LLC
About this paper
Cite this paper
Hokka, M., Kokkonen, J., Seidt, J., Matrka, T., Gilat, A., Kuokkala, VT. (2011). Dynamic Torsion Properties of Ultrafine Grained Aluminum. In: Proulx, T. (eds) Dynamic Behavior of Materials, Volume 1. Conference Proceedings of the Society for Experimental Mechanics Series. Springer, New York, NY. https://doi.org/10.1007/978-1-4419-8228-5_43
Download citation
DOI: https://doi.org/10.1007/978-1-4419-8228-5_43
Published:
Publisher Name: Springer, New York, NY
Print ISBN: 978-1-4419-8227-8
Online ISBN: 978-1-4419-8228-5
eBook Packages: EngineeringEngineering (R0)