© Copyright by International OCSCO World Press. All rights reserved. 2007 VOLUME 24 ISSUE 2 October 2007 Research paper 35 of Achievements in Materials and Manufacturing Engineering of Achievements in Materials and Manufacturing Engineering Dispersion – strengthened nanocrystalline copper J.P. Stobrawa a,b, *, Z.M. Rdzawski a,b a Division of Materials Processing Technology, Management and Computer Techniques in Materials Science, Institute of Engineering Materials and Biomaterials, Silesian University of Technology, ul. Konarskiego 18a, 44-100 Gliwice, Poland b Non-Ferrous Metals Institute, ul. Sowińskiego 5, 44-100 Gliwice, Poland * Corresponding author: E-mail address: jerzys@amme.com Received 23.03.2007; published in revised form 01.10.2007 Materials AbstrAct Purpose: The aim of this work was to investigate microstructure, mechanical properties and deformation behaviour of dispersion strengthened nanocrystalline copper produced by powder metallurgy techniques. Design/methodology/approach: Tests were performed with the Cu, Cu-tungsten carbide and Cu-yttria micro-composites containing up to 3 wt.% of a strengthening particles. The mechanical properties, initial nanocrystalline structures and their evolution during deformation processes were investigated. Findings: The obtained strengthening effect have been discussed based on the existing theories related to strengthening of nanocrystalline materials. The studies have shown the importance of “flows” existing in the consolidated materials and sintered materials such as pores or regions of poor powder particle joining which significantly deteriorate mechanical properties of micro-composites produced by powder metallurgy. Research limitations/implications: The powder metallurgy techniques make it possible to obtain copper-based bulk materials by means of milling input powders in the planetary ball, followed by compacting and sintering. Additional operations of hot extrusion are also often used. There is some threat, however, that during high- temperature processing or using these materials at elevated or high temperatures this nanometric structure may become unstable. Practical implications: A growing trend to use new copper-based functional materials is observed recently world-wide. Within this group of materials particular attention is drawn to those with nanometric grain size of a copper matrix, which exhibit higher mechanical properties than microcrystalline copper. Originality/value: The paper contributes to the mechanical properties of dispersion strengthened (with tungsten carbide and yttria) nanocrystalline copper and to the elucidation of deformation behaviour of these materials with high porosity. Keywords: Nanomaterials; Mechanical properties; Electron microscopy; Metallography; Powder metallurgy 1. Introduction Dispersion – strengthened copper (DSC) is a group of functional and structural materials. They could be used as electrical contact materials in relays, contactors, switches, circuit breaks, resistance–welding tips, continuous casting moulds and so on, where combination of high electrical or/and thermal conductivity with high strength at room and elevated temperatures is required. A growing trend to use such functional materials is recently observed world-wide. Within this group of materials particular attention is drawn to those with nanometric grain size of a copper matrix, which exhibit higher mechanical properties than microcrystalline copper. 1. Introduction