Mechanical alloying and sintering of nanostructured TiO 2 reinforced copper composite and its characterization Y.A. Sorkhe a,⇑ , H. Aghajani a , A. Taghizadeh Tabrizi b a Department of Materials Science and Engineering, University of Tabriz, Tabriz, Iran b Department of Materials Science and Engineering, Sahand University of Technology, Sahand, Iran article info Article history: Received 1 November 2013 Accepted 15 January 2014 Available online 25 January 2014 Keywords: Mechanical alloying Cu–TiO 2 composite Electrical conductivity abstract Mechanical alloying is a suitable method for producing copper based composites. Cu–TiO 2 composite was fabricated using high energy ball milling and conventional consolidation. Ball milling was performed at different milling durations (0–24 h) to investigate the effects of the milling time on the formation and properties of produced nanostructured Cu–TiO 2 composites. The amount of the TiO 2 in the final compo- sition of the composite assumed to be 0, 1, 3, 5 and 7 wt%. The milled composite powders were charac- terized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy to investigate the effects of the milling time on the formation of the composite and its properties. Also hard- ness, density and electrical conductivity of the sintered specimen were measured. High energy ball mill- ing causes a high density of defects in the powders. Thus the Cu crystallite size decreases, generally to less than 50 nm. The maximum hardness value (105 HV) of the sintered compacts belongs to Cu–5 wt%TiO 2 which has been milled for 12 h. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Copper based materials are widely used where high electrical and thermal conductivity are required. Rotating source neutron targets, combustion chamber liners, the electrode of resistance welding and high voltage switches are the applications of interest. These applications require special properties, e.g., high electrical conductivity and excellent mechanical properties at elevated tem- peratures [1–3]. The combination of high electrical conductivity and high hardness is particularly suitable for welding electrodes and sliding contacts. Oxide Dispersion Strengthening (ODS) is a suitable method to improve the mechanical properties of the cop- per matrix composites [4]. Due to high interfacial energy between the molten metal and oxide particles melting and casting tech- niques are not used to fabricate such composites; therefore these composites should be produced by the powder metallurgy meth- ods. The main step of these methods is the production of composite powder, followed by consolidation to get a balk material [5]. The suitable methods for preparing copper based composites are mechanical alloying (MA) and internal oxidation [1,6]. Nanosized particles reinforcing and grain refinement achieved by MA process are very common techniques for producing the copper-based com- posites with high mechanical properties. Therefore, dispersion hard- ening and grain refinement strengthening mechanisms result in the improvement of mechanical properties of these composites [7]. Copper based ODS composites could be reinforced by different fine oxide particles such as Al 2 O 3 and TiO 2 due to their chemical and thermal stability [8]. Cu–Al 2 O 3 composites have been investi- gated by many researchers [1–4], but the Cu–TiO 2 composite has not well studied yet. Warrier and Rohatgi [9] showed that TiO 2 dis- persions can improve the mechanical properties of copper. El-Eskan- darany [10] investigated the possibility of the mechanical solid state reduction (MSSR) of Cu 2 O to metallic Cu using Ti powder as reducing agent and showed that the final product of the MSSR process is a mixture of nanocrystalline Cu and TiO 2 powder. Akarapu [11] showed that wear resistance of Cu–TiO 2 composite coating after a certain amount of sliding is better than Cu–Al 2 O 3 composite coating. In this paper, the fabrication of the copper matrix composite strengthened by nanosized TiO 2 using MA method is expatiated. The effect of the milling time and the amount of TiO 2 content on the structure and properties of the composites were also investigated. 2. Experimental details Powders of copper (Cu; 99.7% purity; average particle size 120 lm), copper (II) oxide (Cu 2 O 99.5% purity; average particle size http://dx.doi.org/10.1016/j.matdes.2014.01.040 0261-3069/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +98 9381638556; fax: +98 411 3354153. E-mail address: yahya.sorkhe90@tabrizu.ac.ir (Y.A. Sorkhe). Materials and Design 58 (2014) 168–174 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes