Hydrostatic Extrusion as a method to produce UFG and NC metals

Waclaw Pachla 

Polish Academy of Sciences, Institute of High Pressure Physics (UNIPRESS), Sokolowska 29/37, Warszawa 01-142, Poland

Abstract

Formation of ultra-fine grained (UFG) or nanocrystalline (NC) structures requires a very large deformations performed at relatively low temperatures (to prevent dynamic recrystallization). To maintain the material integrity during the severe plastic deformation (SPD) a high pressure must be imposed on the workpiece. These conditions require the special methods of mechanical deformation to be applied. Some of them, commonly used, are: high pressure torsion (HPT), equal channel angular pressing (ECAP), cyclic extrusion compression (CEC), cumulative rolling (CR) and multiple forging (MF). They all impose some limitations on researchers, as small volume or limited length, low homogeneity of strain or susceptibility to cracking. Recently, the hydrostatic extrusion (HE) has shown to be an effective SPD method (see EMRS’2005 Conference contributions). It will be demonstrate, that HE satisfies the bulk nanostructures generation criteria, i.e.: high plastic homogenous strain at low deformation temperatures under high imposed (hydrostatic) pressure. Examples of the effective grain refinement in several treated metals and alloys, as aluminium and aluminium alloys, copper, iron, nickel, titanium, stainless steel, and others will be presented. Simultaneous improvement of mechanical properties, such as hardness, tensile strength and yield stress due to refinement and transformation of microstructure during HE will be discussed. Capability of HE process in further increase of strain during deformation improving the properties of metals and alloys will be presented.

Acknowledgment: This communication reports the results of the project supported by the Ministry of Science and Informatics 4 T08A 045 25, 4 T08A 027 24 and PBZ-KBN-096/T08/2003. The author wishes to acknowledge contribution made to this communication by Prof. K. J. Kurzydlowski, Dr. M. Lewandowska, Dr. H. Garbacz, M.Sc. A. Mazur and M.Sc. M. Kulczyk.

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Presentation: invited oral at E-MRS Fall Meeting 2005, Symposium I, by Waclaw Pachla
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-30 12:55
Revised:   2009-06-07 00:44
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