DOI 10.1007/s12289-008-0 - # Springer/ESAFORM 2008 Micro-extrusion of ultrafine grained copper 1 2 3 1 4 S. Geißdörfer , A.Rosochowski , L. Olejnik , U. Engel , M. Richert 1 Chair of Manufacturing Technology, University of Erlangen-Nuremberg, Egerlandstrasse 11, 91058 Erlangen, Germany URL: www.lft.uni-erlangen.de e-mail: Engel@lft.uni-erlangen.de; Geissdoerfer@lft.uni-erlangen.de 2 Department of Design, Manufacture and Engineering Management, University of Strathclyde, 75 Montrose Street, Glasgow, United Kingdom, G1 1XJ URL: www.strath.ac.uk e-mail: a.rosochowski@strath.ac.uk 3 Institute of Materials Processing, Warsaw University of Technology, 85 Narbutta Street, 02-524 Warsaw, Poland www. wip.pw.edu.pl 1 INTRODUCTION Micro technology is gaining an increasing interest due to mobile phones, digital cameras and other consumer electronics products, which become smaller every day. Following this trend, an increasing market for small parts must be satisfied by the production industry. Depending on the required functionality of these parts and the production volume, different manufacturing technologies are available like machining, moulding and forming. In the case of the smallest metallic parts, most of them are produced using machining processes like turning, grinding or milling. For small batch production, machining may be justified. If large quantities of micro-parts are requested, the forming technology is more appropriate due to its high production rate and remarkable accuracy. However, investigations on microforming processes have shown significant differences in the forming behaviour compared to the conventional scale forming, which prevents microforming from being used on a wider scale. Research activities in microforming during the last decade have identified and analyzed the two main size-effects, one with relation to the material flow and another one due to friction. The former can be explained by a dependency of the material flow on the grain size (Hall-Petch effect) and the ratio of the grain size and part's dimensions (contribution of surface grains) [2,3]. The size-effect related to friction has been first investigated using ring upsetting tests scaled-down according to the similarity theorem [4]. A more detailed study has been done using a double cup extrusion test [5,6] which confirmed the previous ABSTRACT: Because of the well known virtues of low cost and high productivity, metal forming technology is well suited for mass production of metal micro-components. However, scaling down metal forming processes proves to be problematic because, among other factors, the relatively coarse grain (CG) structure of micro-billets leads to non-uniform material flow and lack of repeatability during microforming. A substantial grain size reduction below one micron should help to prevent these problems. The aim of the presented study is to investigate a possibility of using an ultrafine grained (UFG) metal for micro-extrusion. The material used for this purpose is CP Cu often used for electrical applications. The UFG version of Cu is produced by severe plastic deformation at room temperature using up to 8 passes of equal channel angular pressing. The microstructure and compression properties of the UFG version of the material are tested. The microforming process of backward extrusion is carried out at room temperature using half cylindrical billets. The extrusion force, grain flow, shape representation and surface quality of the extruded micro-components are compared. Key words: ultrafine grained metal, ECAP, micro-extrusion, in-situ process observation URL: e-mail: l.olejnik@wip.pw.edu.pl 4 Faculty of Non-Ferrous Metals, AGH - University of Science and Technology, Aleja Mickiewicza 30, 30-059 Krakow, Poland URL: www.uci.agh.edu.pl e-mail: mrichert@uci.agh.edu.pl 093 1 Int J Mater Form (2008) Suppl 1:455–458